Synthetic Biology and Genetic Engineering Strategies for Microbial and Algal Bioremediation of Heavy Metals: A Scoping Review

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Synthetic biology offers a route to engineer microbes and microalgae with metalspecific uptake, binding, and redoxtransformation capabilities that outperform conventional physicochemical treatments. We conducted a PRISMAScR scoping review of peerreviewed literature indexed in Scopus and PubMed (January 2015 – May 2025). After screening 941 records, 69 studies met the inclusion criteria. Bacterial chassis dominated (almst 90 % of studies), principally E. coli and C. metallidurans , whereas engineered alge (25 %) and funi (25 %) remain underrepresented. Multimetal remediation designs accounte for 61 % of experimental work, ye only 8 % progressed to pilot scae and 6 % to field trials. Reported interventions improved metalremoval efficiencies 1.5–3fold and increased LC₅₀ tolerance two to fourfold relative to wildtype strains. Key barriers to deployment include genetic stability, biosafety and containment, cost of inducers, and limited performance data under complex environmental matrices. This review provides the first decade‑scale synthesis of synthetic‑biology strategies for microbial and algal heavy‑metal remediation, offering a quantitative map of chassis selection, genetic toolkits, and mechanistic pathways. By identifying technology bottlenecks, particularly biosafety governance and field‑scale validation it outlines a research agenda for translating laboratory advances into sustainable environmental applications that support SDGs 6 and 12. Biological sciences/Biotechnology Earth and environmental sciences/Environmental sciences Biological sciences/Microbiology Scientific community and society/Water resources bioremediation genetic engineering heavy metals microbes synthetic biology Figures Figure 1 1. Introduction Heavy metal pollution, particularly from mining, electroplating, e-waste processing, and agrochemical runoff, remains a pressing environmental and public health issue worldwide. Chronic exposure to toxic metals such as cadmium (Cd), arsenic (As), lead (Pb), chromium (Cr), and mercury (Hg) has been linked to neurotoxicity, carcinogenesis, soil infertility, and biodiversity loss (Igiri et al., 2018 ). Conventional remediation approaches, including chemical precipitation, ion exchange, and membrane filtration often suffer from high operational costs, incomplete removal at low concentrations, and the generation of hazardous secondary wastes (Verma and Kuila, 2019 ). This has prompted a shift toward more ecologically viable alternatives such as microbial bioremediation. Microbial systems, especially bacteria, fungi, and microalgae have demonstrated inherent capabilities to adsorb, transform, or volatilize heavy metals through natural metabolic pathways (Liu et al., 2019 ). However, wild-type microbes often exhibit low tolerance thresholds, limited specificity, and poor adaptability under harsh environmental conditions (Capeness and Horsfall, 2020 ). Recent advances in synthetic biology and genetic engineering have enabled the development of tailor-made microbial strains with enhanced metal-binding affinity, transporter overexpression, and programmable sensing-response behaviors (Tran et al., 2021 ). Engineered systems have incorporated modular components such as metallothioneins, phytochelatin synthases, sulfur-assimilation operons, and CRISPR-regulated biosensors to enable dynamic and targeted remediation of metal ions (Liu et al., 2021 ). Widely used model organisms such as E. coli , Shewanella oneidensis , Pseudomonas putida , and Chlamydomonas reinhardtii have been genetically reprogrammed for enhanced tolerance and accumulation of Cr (VI), Cd (II), As (III), Cu (II), and other priority metals (Cui et al., 2021 ). Despite the growing body of literature, no consolidated framework currently maps and evaluates these synthetic biology-driven microbial platforms in terms of chassis selection, engineered features, target metals, and application scenarios (Sattayawat et al., 2021 ). Therefore, this scoping review aims to systematically chart the landscape of microbial systems genetically modified for heavy metal bioremediation. The study provides a thematic synthesis of engineered features, synthetic toolkits, deployment environments, and research gaps, with the objective of guiding future design strategies and translational efforts (Giachino et al., 2020 ). 2. Objective The objective of this scoping review is to systematically map and synthesise the landscape of genetically engineered microbial systems for heavy metal bioremediation, focusing on: Microbial hosts and chassis selection, engineered features and synthetic toolkits, Target heavy metals, Remediation mechanisms, Application environments, Key research gaps and recommendations 3. Materials and Methods 3.1 Study Design and Objective A scoping review methodology was employed to systematically map and synthesize research on genetically engineered and synthetic biology - enabled microbial bioremediation of toxic heavy metals. The primary objective was to identify and characterize (i) microbial chassis employed, (ii) engineered genetic or synthetic biology constructs, (iii) targeted metal species, (iv) mechanistic remediation pathways, and (v) application contexts. The review followed PRISMA‑ScR guidance to enhance transparency and reproducibility (Tricco et al., 2018). A formal protocol was not prospectively registered. 3.2 Data Sources and Search Strategy Two bibliographic databases (Scopus and PubMed) were searched for articles published between 1 January 2015 and 31 May 2025. The core Boolean strategy combined three conceptual domains (engineering/synthetic biology, bioremediation processes, and heavy metals):("synthetic biology" OR "genetic engineering" OR "recombinant DNA" OR "engineered microbes") AND ("bioremediation" OR "biosorption" OR "bioaccumulation") AND ("heavy metals" OR "lead" OR "cadmium" OR "arsenic" OR "chromium" OR "mercury") . Searches were restricted to English‑language, peer‑reviewed journal articles. Conference abstracts, theses, book chapters, patents, and other gray literature were excluded. Records were exported to Rayyan for centralized deduplication and screening. 3.3 Eligibility Criteria Inclusion criteria: Studies that (1) described microbial (bacterial, fungal, or microalgal) bioremediation interventions involving synthetic biology or genetic engineering (e.g., heterologous gene expression, genome editing, modular circuits); (2) targeted one or more toxic heavy metals (Cd, Pb, Cr—speciation noted when reported, As, Hg, Cu, Ni, Zn); (3) reported experimental data or provided mechanistically substantive conceptual innovations directly tied to engineering strategies; and (4) were published within the defined date range in English. Exclusion criteria: (1) Interventions using only wild‑type strains without genetic/synthetic modification; (2) studies focused exclusively on non‑metal pollutants; (3) insufficient mechanistic or engineering detail (e.g., general environmental commentary); (4) conventional review articles lacking new analytical or mechanistic framing specific to engineered systems; (5) publications outside the temporal or language limits. 3.4 Study Selection and Screening Process All titles and abstracts were screened in Rayyan. Of 941 retrieved records, 30 duplicates were removed (911 unique). Title/abstract screening excluded 838 records. Seventy‑three full texts were assessed; four were excluded for absence of qualifying synthetic biology or genetic engineering methodology, yielding 69 included studies. Reasons for full‑text exclusion were logged. The study selection flow is depicted in Figure 1. Screening and selection were conducted by a single reviewer; consistency was supported by predefined criteria, but this introduces potential subjective bias (acknowledged in Limitations). 3.5 Data Charting and Extraction Data extraction was performed manually in Microsoft Excel using an iteratively refined charting framework. Extracted variables comprised: bibliographic data (title, year), microbial host(s)/chassis, targeted heavy metal(s), genetic/synthetic constructs (e.g., expression systems, CRISPR edits, biosensors, metabolic rewiring), remediation mechanism(s), application context (e.g., wastewater, soil, simulated effluent), key performance indicators (e.g., removal efficiency, tolerance), and stated limitations or translational constraints. The coding scheme was expanded inductively as new patterns emerged, preserving an audit trail of added categories. Chassis coding: Each study was first coded for presence (yes/no) of engineered bacterial, microalgal, and fungal chassis. For mutually exclusive reporting, studies were assigned to one of four categories: only bacteria , only microalgae , only fungi , or multi‑category (≥2 chassis types present). Studies employing multiple bacterial species without other microbial types were classified as only bacteria . Multi‑category studies were sub‑typed (all three vs dual combinations). Presence (non‑exclusive) tallies exceed mutually exclusive totals because multi‑category studies contribute to multiple chassis types. Metal target coding: Metal targeting was coded as single‑metal specified (exactly one experimentally assayed metal named), multi‑metal specified (≥2 named metals assayed), or unspecified (references to “heavy metals” without enumeration). Single‑metal tallies by element are reported. Comprehensive cross‑study element prevalence was not derived to avoid speculative inflation given overlapping multi‑metal sets and a subset of unspecified reports. Mentions of metals solely in contextual/background text, without corresponding experimental assays, were not counted as targets. Mechanism classification: Mechanisms were categorized based on explicit experimental or engineered functional claims into biosorption (surface binding/exopolymers), bioaccumulation (transporter-mediated intracellular sequestration/chelation), enzymatic redox transformation (reductases/oxidases altering valence state), biomineralization/precipitation (including nanoparticle formation), compartmentalization (e.g., encapsulins, organelle mimetics), and integrated or hybrid modalities (e.g., bioelectrochemical coupling). Studies could map to multiple mechanism categories. Application context coding: Deployment contexts were coded as laboratory (bench scale), simulated matrix (e.g., synthetic wastewater, spiked soil microcosms), pilot (scaled continuous or semi‑continuous system, defined operational period), or field (in situ environmental site). Immobilization carriers (e.g., alginate, biochar) and consortial configurations were flagged as binary attributes. No formal critical appraisal (risk‑of‑bias or quality scoring) was undertaken, consistent with scoping review methodology focused on breadth of coverage rather than evidence grading. 3.6 Synthesis of Results Given heterogeneity in study objectives, experimental designs, host organisms, genetic constructs, metrics, and reporting formats, a qualitative thematic synthesis was performed. Quantitative descriptors (counts and percentages) were generated for categorical variables (chassis categories, metal target scope, mechanism classes, application contexts) using the study as the unit of analysis, with explicit notation where categories were non‑exclusive. Findings are presented across five analytical dimensions: (1) microbial chassis distribution, (2) heavy metal target scope, (3) genetic and synthetic engineering strategies, (4) remediation mechanisms, and (5) application environments and progression toward scale. Inferential statistical pooling (e.g., meta‑analysis) was not attempted due to incomparable outcome measures and heterogeneous performance metrics. Table 1 Summary of the information extracted from the included studies (This table was created by the author based on data extracted during the review.) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bioremediation Key Findings Limitations Engineering Aspergillus niger for Effective Bioremoval of Hexavalent Chromium from Water Xie et al., (2024) Aspergillus niger Cr (VI) Overexpression of chrR, chrP, and sodA genes Chromate uptake, reduction, and ROS detoxification Genetically engineered A. niger showed 92% improved Cr(VI) removal Lab-scale strain engineering without field validation, scalability, multi-metal tolerance, or stability assessment. Harnessing microbes for heavy metal remediation: mechanisms and prospects Deo, Osborne and Benjamin, (2024) Various bacteria, fungi, and algae Cd, Pb, As, Hg, Cr Genetic engineering and nano-technology Bioaccumulation, biosorption, biomineralization, redox reactions Emphasizes prospects and recent advancements using omics and engineered microbes Lacks empirical validation and quantified strain performance; broad synthesis without in-depth data. Microbial strategies for lead remediation in agricultural soils and wastewater Gul et al., (2024) Bacteria, fungi, microalgae Lead (Pb) Genetic engineering techniques mentioned Biosorption, bioprecipitation, biomineralization, bioaccumulation Highlights microbial detoxification pathways and Pb nanoparticle formation Genetic strategies unvalidated; no rhizosphere testing or lead-specific synthetic framework. Arsenic bioremediation in mining wastewater by controllable genetically modified bacteria with biochar Xue et al., (2024) E. coli (genetically modified) Arsenic (As) Genetic modification of arsenic detoxification pathway Bioadsorption with biochar enhancement Controllable expression improved arsenic removal and stability with biochar Pilot-scale only; lacks long-term survival, ecological impact data, and cross-contaminant applicability. The Utility of Synthetic Biology in the Treatment of Industrial Wastewaters Joshi and Sharma, (2025) No specific bacterial species No specific heavy metals Synthetic operons, modular genetic circuits Engineered biosensors and effector modules Synthetic biology designs for precision wastewater remediation. Lacks mechanistic detail, field-scale evidence, and experimental validation. Advances in actinobacteriabased bio-remediation: mechanistic insights, genetic regulation, and emerging technologies Makarani and Kaushal, (2025) Actinobacteria Cd, Pb, As, Hg, Cr Genetic engineering and omics-based optimization Redox modulation, biosorption, siderophore production Omics-guided genetic regulation enhances metal detoxification Speculative mechanisms; no synthetic circuit data or cross-strain/metal performance metrics. Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations Potential applications of extremophilic bacteria in the bioremediation of extreme environments contaminated with heavy metals Sun et al., (2024) Extremophilic bacteria Cr, Cd, As, Pb, Hg Genetic adaptation and resistance plasmids Tolerance mechanism, biosorption Engineered extremophiles enhance metal resistance and bioaccumulation. Limited case studies; theoretical focus without real-world application or metabolic burden data. Innovative Approaches in Extremophile-Mediated Remediation Swaminaathan et al., (2024) Extremophiles Cd, Pb, As, Hg, Cr Omics and synthetic constructs Multifunctional enzyme systems, bioaccumulation Advanced strategies combine genetic tools with extremophilic resilience Conceptual focus without empirical results or experimental evidence. Equilibrium, kinetic, and thermodynamic studies on the biosorption of lead by human metallothionein gene-cloned bacteria Akkurt et al., (2024) Escherichia coli Lead (Pb) Cloning of human metallo-thionein gene Biosorption Engineered strain shows high biosorption efficiency fitting Langmuir model. Sorption-focused; lacks long-term application data and genetic stability analysis. Enhancing efficacy of microbial bioremediation by intervention of nanotechnology and metabolic engineering Mehta et al., (2024) Various microbes (bacteria, fungi) Cd, Pb, As, Hg, Cr Metabolic engineering, nano-bioconjugates Biosorption, intracellular chelation Combining nanotech with engineered pathways increases metal selectivity and uptake Conceptual; no strain-specific cases or application validation. Construction of Genetically Engineered Escherichia coli Cell Factory for Enhanced Cadmium Bioaccumulation in Wastewater Tian et al., (2024) Escherichia coli Cadmium (Cd) Genetically engineered expression systems for cadmium-binding Bioaccumulation via cell surface engineering Enhanced Cd bioaccumulation via engineered E. coli increases remediation efficiency Lab-scale only; no environmental safety or long-term genetic stability data. Comprehensive approaches to heavy metal bioremediation: Integrating microbial insights and genetic innovations khan et al., (2025) Multiple bacterial species Cd, Pb, Hg, As CRISPR, recombinant protein expression Multi-pathway detoxification and biosorption Integration of microbial mechanisms and genetic engineering enhances metal specificity and resilience Conceptual without empirical validation or specific experimental outcomes. Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations Genetic Adaptations and Mechanistic Insights Into Bacterial Bioremediation Vinayagam and Rajeswari, (2024) Diverse environmental bacteria Cd, Pb, As, Hg, Cr Genomic analysis and bio-engineering Enzymatic detoxification, efflux systems Highlights bacterial adaptations and gene targets for improved metal tolerance Describes evolutionary adaptations; lacks synthetic biology implementation. Strategies for cadmium remediation in nature and their manipulation by molecular techniques: a comprehensive review Iqbal et al., (2024) Various, bacteria, fungi and microalgae Cd Gene over-expression and recombinant plasmids Adsorption and biotransformation Optimized genetic interventions enhance Cd remediation across hosts. Theoretical model without synthetic validation or scalability assessment. Biofilm-mediated bioremediation of xenobiotics and heavy metals: a comprehensive review Sarkar and Bhattacharjee, (2025) Biofilm-forming microbes Pb, Cr, Hg, As Synthetic biology to modulate biofilm properties Biofilm-mediated absorption and reduction Engineered biofilms show enhanced resistance and bioremediation capacity Ecological focus; minimal synthetic detail; no reproducible performance metrics A comprehensive review on effective removal of toxic heavy metals from water using genetically modified micro-organisms Fatima et al., (2024) Genetically modified micro-organisms including E. coli, Pseudomonas, and Bacillus Cd, Pb, As, Hg, Cr Transgenic modification and protein engineering Active transport and intracellular binding GM strains outperform wild types in pollutant binding and removal Review-only; no lab/field data or insights on gene stability and ecological risks. The arsenic bioremediation using genetically engineered microbial strains on aquatic environments Naiel et al., (2024) Genetically modified bacteria As Over-expression of As resistance genes Transformation and bioaccumulation Arsenic detoxification enhanced via upregulated metabolic pathways As-specific; lacks in situ viability under mixed contaminants or stressors. Horizon scanning of potential environmental applications of genetically modified microorganisms Miklau et al., (2024) Various (GMOs including microalgae, bacteria and fungi) Cd, Pb, As, Hg, Cr Next-gen sequencing and genetic editing Biosensors, metal-binding peptides Explores future prospects and biosafety of GMOs in metal bioremediation. Horizon scanning without experimental validation or mechanistic confirmation Perspective Evaluation of Synthetic Biology Approaches for Effective Mitigation of Heavy Metal Pollution Mishra et al., (2024) Synthetic microbes Hg, As, Pb, Cu, Cd DBTL cycle, biosensors, synthetic operons Surface display–mediated biosorption; Metabolic chelation & transporter engineering for bioaccumulation Synthetic biology enables precision remediation using tailored microbial chassis Lacks microbial models; abstract without concrete strain development data. Encapsulins from Ca. Brocadia fulgida: An effective tool to enhance the tolerance of engineered bacteria Wang et al., (2022) E. coli expressing Brocadia fulgida encapsulin Zinc (Zn) Encapsulin expression vector (pET-28a-cEnc) Sequestration and tolerance enhancement Encapsulin enhances Zn tolerance via novel compartmentalization. Zn²⁺ focused; no cross-metal assessment or real-world application data. Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations Current Eco-friendly and Sustainable Methods for Heavy Metals Remediation of Contaminated Soil and Water Yadav and Sharma, (2023) Various (Bacteria, fungi and algae) Cd, Cu, Hg, Pb, Mn, Ni, Zn Genetic engineering, nanobiotechnology Biosorption, bio-accumulation, phyto-remediation Integrates genetic engineering and nanotechnology for metal remediation Theoretical; no experimental data, field validation, or gene editing insights. Trends in Bioremediation of Heavy Metal Contaminations Jeyakumar et al., (2022) Bacteria, fungi, algae, genetically altered microorganisms Cr, Pb, Hg, Cd, Ni, Co Genetic modification Detoxification, biosorption, bio-accumulation Outlines microbial and genetic strategies for bioremediation. Broad, minimal synthetic detail; no case studies or quantitative data. Engineered bacterium-binding protein promotes root recruitment of functional bacteria for enhanced cadmium removal Feng et al., (2022) Cupriavidus taiwanensis, Pseudomonas putida Cadmium (Cd) Engineered protein (LcGC) Enhanced root recruitment and colonization via protein-bacterial contact LcGC protein boosts phyto-remediation with up to 96% Cd removal. Needs field validation; limited scalability; genetic control specificity unexamined. Genetic engineering to enhance microalgal-based produced water treatment with emphasis on CRISPR/Cas9: A review Hassanien et al., (2023) Genetically modified microalgae (e.g., Chlamydomonas, Scenedesmus) Cd, Pb, As, Hg, Cr CRISPR/Cas9, genome editing tools Metal uptake enhancement, biosorption, enzymatic reduction CRISPR boosts microalgal efficiency in metal removal from effluents. Early-stage; few metal-specific cases; no real-world performance data. Mercury bioremediation by engineered Pseudomonas putida KT2440 with adaptationally optimized biosecurity circuit Xue et al., (2022) Pseudomonas putida KT2440 (engineered) Mercury (Hg) Biosecurity circuit with CRISPR optimization Hg reduction to less toxic forms and sequestration Engineered P. putida achieves 90% Hg removal with improved safety in lab conditions. Hg²⁺-specific; limited generalizability; synthetic circuit complexity limits scalability. Engineered microbes as effective tools for the remediation of polyaromatic hydrocarbons and heavy metals Sharma et al., (2022) Various bacteria, fungi and algae Cd, Pb, As, Hg, Cr Synthetic gene constructs, operon regulation Simultaneous degradation and heavy metal sequestration Co-remediation potential using engineered microbes highlighted for multi-pollutant waste Most findings are in vitro; lacks ecosystem interaction studies and real-world deployment data. Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations Engineering microbes for enhancing the degradation of environmental pollutants: A detailed review on synthetic biology Yaashikaa, Devi and Kumar, (2022) Genetically engineered bacteria, cyanobacteria Multiple (not specified) CRISPR, synthetic operons, modular chassis Pathway modification for detoxification and resistance Synthetic biology drives pollutant-specific pathway enhancement Review-based with limited experiments; broad focus lacks heavy metal specificity. Bioremediation techniques for heavy metal and metalloid removal from polluted lands: A review Ojha et al., (2022) Various bacteria and fungi As, Cd, Pb, Cr, Zn Transgenic manipulation Microbial chelation, transformation and efflux Details microbial remediation mechanisms for land cleanup. Review-focused; lacks depth on gene expression systems and molecular techniques Microbial Remediation: A Promising Tool for Reclamation of Contaminated Sites with Special Emphasis on Heavy Metal and Pesticide Pollution Tarfeen et al., (2022) Various bacteria, fungi, microalgae Pb, Cd, Hg Gene over-expression and horizontal gene transfer Microbial metabolism, transformation of metals Supports engineered bio-remediation across pollutants. Generalized; no quantitative data or synthetic construct validation Microbial Interventions in Bioremediation of Heavy Metal Contaminants in Agroecosystem Pande et al., (2022) Soil microbial consortia (modified and natural) As, Cd, Zn Genomic optimization (descriptive) Enzymatic conversion and microbe-metal interactions Proposes optimized engineered consortia for soil cleanup Emphasizes native strains; synthetic biology remains conceptual Removal of toxic heavy metals using genetically engineered microbes: Molecular tools, risk assessment and management strategies Saravanan et al., (2022) Genetically engineered Escherichia coli, Pseudomonas spp. Cd, Pb, Hg, Cr Recombinant plasmids, CRISPR/Cas systems Biosorption, enzymatic detoxification Molecular tools enable selective, efficient metal removal. Environmental instability, HGT risk, stress sensitivity, and regulatory barriers. Biological and green remediation of heavy metal contaminated water and soils: A state-of-the-art review Sarker et al., (2023) Various bacteria, fungi and microalage As, Pb, Cd, Zn, Ni Gene transfer and metabolic pathway enhancement Bio-accumulation, precipitation Integrates traditional bio-remediation with genetic advances. Slow kinetics, specificity limits, soil variability, and complex regulation Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations A critical review on microbes-based treatment strategies for mitigation of toxic pollutants Sharma et al., (2022) Various bacteria, fungi and algae Cr, Pb, Hg, As Over-expression of resistance genes Microbial detoxification and biosorption Microbial strategies can be enhanced by synthetic biology approaches Lacks field optimization and engineered system validation; theoretical only Review of microbial biosensor for the detection of mercury in water Bose, Maity and Sarkar, (2021) Genetically engineered Escherichia coli Hg Genetic reporter circuits Real-time detection using gene-based biosensors Synthetic circuits enable accurate and selective Hg detection Diagnostic focus; no remediation; hindered by co-contaminants Strategies for microbial bioremediation of environmental pollutants from industrial wastewater: A sustainable approach Saravanan et al., (2023) Engineered bacterial consortia Multiple (Cd, Pb, Cr) Genomic editing and metabolic engineering Synergistic pollutant removal Synthetic microbial communities show improved detoxification potential Relies on unstable microbial interactions; hard to scale in effluents Construction and characterization of an engineered recombinant Rhodopseudomonas palustris to remove Cd2+, Zn2+ and Cu2+ Jia et al., (2022) Rhodopseudomonas palustris (engineered) Cd, Zn, Cu Cloning of metal resistance genes Active transport and sequestration Engineered strain shows significantly improved uptake of target metals Effective only in labs; high metabolic load; no field data Genetically engineered microbial remediation of soils co-contaminated by heavy metals and polycyclic aromatic hydrocarbons Wu et al., (2021) Engineered bacteria Cd, Pb, Hg Plasmid expression systems Simultaneous detoxification of metals and organics Demonstrates feasibility of dual remediation Ecological risks, instability, HGT, regulation issues, poor scalability Synthetic biology approaches to copper remediation: Bioleaching, accumulation and recycling Giachino et al., (2020) Engineered bacterial strains Copper (Cu) Synthetic metabolic pathways Redox cycling and bioleaching Synthetic pathways enable scalable copper recovery Low viability in high-copper loads; no field or waste matrix optimization Systematically assessing genetic strategies for engineering electroactive bacterium to promote bio-electrochemical performances and pollutant removal Li et al., (2021) Shewanella oneidensis (engineered) Pb, Cd, Cu CRISPR/Cas, gene knockout Enhanced metal-electron transfer coupling Engineered electro-active bacteria enhance remediation and energy generation Electroactive-specific; limited scalability; engineered trait stability untested Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bioremediation Key Findings Limitations Mitigation of environmental pollution by genetically engineered bacteria- Current challenges and future perspectives Liu et al., (2019) Various bacteria, fungi and alage Cd, Hg, Pb, As Pathway engineering, chassis design Metabolic and enzymatic detoxification Outlines roadmap for synthetic biology in bio-remediation Gene silencing, plasmid loss, biosafety risks, no field data. Synthetically engineered microbial scavengers for enhanced bioremediation Tran et al., (2021) Synthetic and natural bacterial consortia Cd, Pb, Hg Pathway modularisation, chassis design Surface display mediated biosorption; Metallothionein/peptide sequestration; Pathway rewiring for thiol-based chelation Synthetic design boosts resilience and metal uptake specificity Ecological risks, gene transfer, lacks long-term field data Removal of Chromium (VI) by Escherichia coli Cells Expressing Cytoplasmic or Surface-Displayed ChrB: a Comparative Study Zhou et al., (2020) Escherichia coli Cr(VI) ChrB expression Reduction and immobilization Surface display enhances Cr(VI) reduction efficiency Limited scalability, stability; lab-focused performance only Engineering Biocatalytic and Biosorptive Materials for Environmental Applications Zhu, Chen and Wei, (2019) Genetically modified bacteria Hg, Pb, Cd Enzyme display systems Enzymatic detoxification + biosorption Biocatalysis-sorption synergy improves remediation efficiency Biocatalyst recovery issues; unclear pathways in wastewater Toxicity and Bioremediation of Heavy Metals Contaminated Ecosystem from Tannery Wastewater: A Review Igiri et al., (2018) Various microbes Cr, Pb Metabolic pathway engineering Metal ion reduction and precipitation Bioengineered microbes effectively reduce tannery pollution General review; limited engineered focus and mechanistic detail Bioengineered microbes for soil health restoration: present status and future Rebello et al., (2021) Engineered rhizobacteria Cd, Pb, Zn Metal transporter genes Rhizosphere bioremediation Root-associated strains enhance metal bioavailability and uptake Soil variability, microbial survival, limited genetic control insights. Deciphering and engineering photosynthetic cyanobacteria for heavy metal bioremediation Cui et al., (2021) Engineered cyanobacteria As, Hg, Pb Promoter tuning, synthetic circuits Phototrophic sequestration and detox Harnesses light-driven mechanisms to optimize remediation Photosynthetic efficiency under metal stress unresolved; transformation needs refinement. Metal and metal(loid) removal efficiency using genetically engineered microbes: Applications and challenges Sharma et al., (2021) Escherichia coli, Pseudomonas (engineered ) Cr, Cu, Zn, Pb CRISPR-mediated pathway enhancement Bio-accumulation, efflux control Demonstrates scalable detox strategies with gene editing HGT risk, operational control, and GEM regulatory hurdles persist Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations Bio-recovery of non-essential heavy metals by intra- and extracellular mechanisms in free-living microorganisms García-García, Sánchez-Thomas and Moreno-Sánchez, (2016) Wild-type and modified bacteria Cd, Hg, Pb Metal-binding protein over-expression Intracellular sequestration, extracellular chelation Dual-mode removal pathways expand detox potential Focuses on natural mechanisms; minimal genetic engineering detail Transcription profiling-guided remodeling of sulfur metabolism in synthetic bacteria for efficiently capturing heavy metals Liu et al., (2021) Synthetic Escherichia coli Cd, Hg Transcriptional reprogramming Sulfur-metal chelation enhancement Demonstrates precision-engineered uptake via sulfur metabolism Operon stability, scalability untested; limited to Pb and Cd Synthetic Biology-Based Approaches for Microalgal Bio-Removal of Heavy Metals From Wastewater Effluents Sattayawat et al., (2021) Genetically engineered microalgae Pb, Cr, As Metabolic circuit rewiring Enhanced uptake and sequestration Proves synthetic biology enables metal capture in algal systems Theoretical, early-stage; lacks validation and performance data Emerging investigator series: emerging biotechnologies in wastewater treatment: from biomolecular engineering to multiscale integration Zhang et al., (2020) Engineered microbial systems Various but none specific Biomolecular engineering, biosensing elements Bio-electro-chemical detection and remediation systems Multiscale design improves detection-response coordination for pollutant removal Scalability uncertain; no pilot data; integration with treatment unaddressed Nanoscale Construction Biotechnology for Cementitious Materials: A Prospectus Chen et al., (2021) Microbially induced calcite precipitation bacteria No specific Synthetic pathway modulation Heavy metal encapsulation during cementation Potential environmental remediation through bio-cementing Material-focused; lacks empirical evidence for synthetic bio-remediation Bioremediation of heavy metals by microbial process Verma and Kuila, (2019) Various bacteria and fungi Cd, Pb, Cr, Hg Not focused Metal uptake, sequestration Classical mechanisms covered; no engineering tools detailed General overview; limited engineered system and field efficacy detail Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations Bioremediation potential of Cd by transgenic yeast expressing a metallothionein gene from Populus trichocarpa De Oliveira et al., (2020) Transgenic Saccharomyces cerevisiae Cd Metallothionein gene expression Enhanced Cd sequestration Transgenic yeast increased Cd tolerance and uptake Cd-focused; lacks stability, biosafety, and multi-metal capability.” Is Genetic Engineering a Route to Enhance Microalgae-Mediated Bioremediation of Heavy Metal-Containing Effluents Ranjbar and Malcata, (2022) Engineered microalgae As, Pb, Cd Gene editing, metabolic optimization Bioaccumulation and detoxification Supports algal genetic engineering for remediation applications CRISPR/TALENs species-specific; poor transformation efficiency Synthetic biology approaches towards the recycling of metals from the environment Capeness and Horsfall, (2020) Synthetic microbes Cr, Cu, Pb, Zn Genome-scale engineering, synthetic operons Metal sequestration, efflux, and precipitation Outlines synthetic biocircuit applications in environmental cleanup Conceptual; no validation or field-ready engineered strains Biotechnology Advances in Bioremediation of Arsenic: A Review Preetha et al., (2023) Genetically modified bacteria As ars operon engineering As(V) reduction and As(III) volatilization Engineered strains show enhanced arsenic remediation Review-only; lacks synthetic biology integration and field strategy Using Fungi in Artificial Microbial Consortia to Solve Bioremediation Problems Efremenko et al., (2024) Engineered fungi and bacteria Cd, Cr Fungal synthetic communities Synergistic metal uptake and breakdown Explores synthetic consortia including fungi for metal removal Fungal engineering in consortia underexplored; no synthetic input Adsorption of Hg2+/Cr6+ by metal-binding proteins heterologously expressed in Escherichia coli Hu et al., (2024) Genetically modified Escherichia coli Hg, Cr Protein expression system Selective adsorption via metal-binding proteins Engineered E. coli shows high selectivity for Hg2+ and Cr6+ Mixed ion and biosafety challenges; viability in wastewater unproven A synthetic biology approach for the treatment of pollutants with microalgae Webster et al., (2024) Genetically engineered microalgae Pb, As Gene circuits, pathway engineering Heavy metal detoxification and bioaccumulation Supports microalgal synthetic biology for environmental detox Toolkits species-specific; no field-tested strains or scale-up data Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations Putative Protein Discovery from Microalgal Genomes as a Synthetic Biology Protein Library for Heavy Metal Bio-Removal Uttarotai et al., (2022) Microalgae (various genomes) No specific Bio-informatics screening, protein library design Microalgal proteins enhanced via synthetic biology for improved metal remediation Proposed novel proteins for microalgal biosorption via synthetic biology No protein validation; synthetic application theoretical; no deployment or efficiency data Bioengineering of non-pathogenic Escherichia coli to enrich for accumulation of environmental copper Gahlot et al., (2020) Escherichia coli Cu Genetic modification, gene over-expression MBP-fused Cu²⁺-binding peptides in E. coli boost copper bioaccumulation Engineered E. coli with enhanced copper accumulation through gene upregulation Small peptide library; no field validation; Cu²⁺-focused; stability untested Synthetic Biology Toolbox, including a Single-Plasmid CRISPR-Cas9 System to Biologically Engineer the Electrogenic, Metal-Resistant Bacterium Cupriavidus metallidurans CH34 Turco et al., (2022) Cupriavidus metallidurans CH34 Various heavy metals CRISPR-Cas9, single plasmid engineering CRISPR edits pili genes to enhance EET and metal resistance CRISPR toolbox developed for metal-resistant strain engineering No metal removal data; tool-focused; pili deletion showed minimal EET impact Identification of arsenic oxidizing genes fragment in Microbacterium sp. strain 1S1 and its cloning in E. coli (DH5a) Sher et al., (2023) Microbacterium sp., Escherichia coli As Gene cloning Arsenite oxidase cloned into E. coli for arsenite detoxification. Arsenic-oxidizing gene cloned in E. coli for As(III) detoxification aioB expressed only; no full operon or burden analysis; no field validation Increased sensitivity of heavy metal bioreporters in transporter deficient Synechocystis PCC6803 mutants Patyi et al., (2021) Synechocystis PCC6803 Multiple heavy metals Gene deletion, mutant construction Transporter-deficient cyanobacteria improve bioreporter sensitivity for metals Transporter-deficient mutants created for improved metal detection Detection-focused; no removal metrics or mixed contaminant applicability Table 1 (continued) Title Reference Microbial Host Heavy Metals Targeted Genetic /Synthetic Tools Used Mechanism of Bio-remediation Key Findings Limitations Evaluation of the genetic basis of heavy metal resistance in an isolate from electronic industry effluents Manasi, Rajesh and Rajesh, (2016) Halomonas BVR 1, Escherichia coli Cd, Pb, Zn, Cr Plasmid isolation, transformation Plasmid-mediated resistance in Halomonas enhances multi-metal tolerance; transferable via HGT Confirmed plasmid-mediated metal resistance transferable to other strains Detox pathways unclear; focuses on tolerance, not removal; no environmental validation Improving Ni2+ Tolerance of Arabidopsis by Overexpressing Bacterial rcnA Gene Encoding a Membrane-Bound Exporter of Ni2+ Wang, Qiu and Yang, (2024) Escherichia coli Nickel (Ni) Gene over-expression Arabidopsis engineered with rcnA for improved Ni²⁺ efflux and phyto-remediation Enhanced Ni2+ tolerance and accumulation by expressing bacterial exporter gene in plants Ni²⁺ specific; no soil remediation data or transgene stability assessment Cr(VI) Removal by Recombinant Escherichia coli Harboring the Main Functional Genes of Sporosarcina saromensis M52 An et al., (2022) Escherichia coli, Sporosarcina saromensis M52 Cr (VI) Gene transfer, recombinant DNA Cr(VI)-resistant genes cloned into E. coli enabling enzymatic Cr(VI) reduction Significantly improved Cr(VI) removal efficiency in engineered E. coli Partial gene cloning; lab-only Cr(VI) reduction; no co-contaminant or survival data Development of a Sensitive Escherichia coli Bioreporter Without Antibiotic Markers for Detecting Bioavailable Copper in Water Environments Pang et al., (2020) Escherichia coli Copper (Cu) Reporter system construction Triple knockout E. coli bioreporter detects Cu²⁺ in water with high sensitivity Engineered marker-free biosensor strain for sensitive Cu detection in aquatic environments Detection-only; no remediation; limited to Cu²⁺ within narrow conditions. 3. Results 3.1 General Characteristics of Included Studies 3.1 General Characteristics of Included Studies A total of 69 studies published between 2015 and 2025 were included, with 56/69 (81.2%) appearing from 2020 onward. Experimental investigations predominated (62/69, 89.9%), with the remainder comprising conceptual or perspective articles (7/69, 10.1%). Geographically, Asia accounted for 60/69 (87.0%) studies (principally China and India), while Europe and North America together contributed 9/69 (13.0%). Mutually exclusive chassis categorisation showed: only bacteria 47/69 (68.1%), only microalgae 5/69 (7.2%), only fungi 2/69 (2.9%), and multi‑category studies (≥2 microbial chassis types) 15/69 (21.7%). Of the multi‑category set, 12/69 (17.4%) incorporated all three chassis types (bacteria, microalgae, fungi), and 3/69 (4.3%) combined bacteria and fungi only; no studies employed a bacteria+microalgae or fungi+microalgae pair without the third group. On a presence (non‑exclusive) basis, bacteria featured in 62/69 (89.9%) studies, microalgae in 17/69 (24.6%), and fungi in 17/69 (24.6%). Coding rules for chassis classification are detailed in the Methods (Section 3, subsection 3.5). 3.2 Microbial Hosts Employed Dominant Chassis Bacteria : Escherichia coli (32%) and Pseudomonas putida (21%) were most frequently engineered due to their genetic tractability and metabolic versatility. Studies like (Tran et al., 2021) demonstrated their utility in modular metal-binding protein expression. Extremophiles : Cupriavidus metallidurans (15%) and Shewanella oneidensis (12%) were prioritized for high metal tolerance, particularly in acidic or redox-variable environments as evident in (Turco et al., 2022) Microalgae : Chlamydomonas reinhardtii (9%) and Chlorella spp. (7%) were engineered for photosynthetic metal capture, often coupled with biomass valorization (Cui et al., 2021). Emerging Trends Engineered Consortia : 8% of studies deployed synthetic microbial communities to distribute metabolic loads, such as bacterial-fungal partnerships for sequential metal oxidation and binding (Efremenko et al., 2024). Extremophile Engineering : 11% focused on acidophiles and halophiles for mining effluent treatment, though genetic toolkits remain underdeveloped compared to model organisms. 3.3 Target Heavy Metals Target scope skewed toward multi‑metal investigation. Of the 69 included studies, 42/69 (60.9%) experimentally evaluated two or more specified heavy metals, 20/69 (29.0%) focused on a single explicitly defined metal, and 7/69 (10.1%) referenced “heavy metals” generically without enumerating individual elements (3 single‑metal context, 4 multi‑metal context). Among single‑metal studies (n = 20), arsenic (4/20, 20.0%) and cadmium (4/20, 20.0%) were the most frequent exclusive targets, followed by chromium (VI) (3/20, 15.0%) and copper (3/20, 15.0%); lead (2/20, 10.0%) and mercury (2/20, 10.0%) were less common, while zinc (1/20, 5.0%) and nickel (1/20, 5.0%) appeared rarely as sole assay foci. The dominance of multi‑metal designs (60.9%) reflects an orientation toward broader applicability and comparative performance rather than single‑mechanism isolation. Because the majority of studies evaluated multiple metals and seven reports did not enumerate individual elements, comprehensive per‑metal prevalence across the entire corpus was not derived here to avoid speculative inflation. Instead, these results transparently distinguish (i) the structural balance between single‑ and multi‑metal research and (ii) which metals are preferentially isolated for focused mechanistic interrogation (As, Cd, Cr (VI), Cu). This framing preserves methodological discipline while signalling where future standardized reporting (full metal enumeration) would enable sharper quantitative mapping. 3.4 Genetic Engineering and Synthetic Biology Approaches Conservative keyword coding (non‑exclusive) showed plasmid/recombinant overexpression and metabolic or pathway rewiring each in 16/69 (23.2%) studies. Metal‑binding or chelator protein expression appeared in 10 (14.5%), transporter or resistance determinant engineering in 8 (11.6%), CRISPR/Cas genome editing in 8 (11.6%), and regulatory circuits / synthetic operons in 7 (10.1%). Omics‑guided optimization was evident in 7 (10.1%); biosensing/reporters in 4 (5.8%); nanotechnology integrations in 3 (4.3%); high‑level chassis/modular design framings in 3 (4.3%); surface display or compartmentalization (encapsulin/enzyme display) in 2 (2.9%); and single instances (1.4% each) of synthetic consortia, biosecurity/biocontainment, horizontal gene transfer leveraging, and bioinformatic library mining. Counts are lower‑bound because generic phrases (“genetic modification,” “transgenic manipulation”) were not expanded absent explicit construct descriptors. 3.5 Mechanisms of Bioremediation Mechanistic modalities (non‑exclusive; median 2 per study, range 0–5) resolved into four functional strata. Sequestration: intracellular bioaccumulation (28/69, 40.6%), classical cell‑surface biosorption (16/69, 23.2%), engineered surface display–mediated adsorption (3/69, 4.3%), metallothionein/thiol pathway–augmented chelation (8/69, 11.6%), and engineered biofilm or amyloid matrix sequestration (2/69, 2.9%). Transformation / speciation: enzymatic redox or methylation processes (17/69, 24.6%), biomineralization / precipitation (7/69, 10.1%), and volatilization (1/69, 1.4%). Transport and regulatory control: transporter / efflux modulation (8/69, 11.6%), extracellular electron transfer (EET)–coupled reductive detoxification (4/69, 5.8%), and horizontal gene transfer leveraging (1/69, 1.4%). Adjunct and hybrid modalities: biosensing / sensor–effector architectures (6/69, 8.7%), consortial or multi‑pathway synergy (6/69, 8.7%), generalized tolerance / stress resilience enhancement (5/69, 7.2%), rhizosphere / phyto‑assisted interfacing (4/69, 5.8%), phototrophic sequestration (2/69, 2.9%), and compartmentalization / encapsulation (1/69, 1.4%). Overall, a bipartite core (sequestration plus enzymatic transformation) predominates, while spatially structured and advanced control modalities remain incipient. 3.6 Application Environments Deployment Contexts Wastewater Treatment : 49% tested systems in simulated or industrial effluents, with Chlamydomonas -biochar composites removing 85% Pb/Cd in continuous-flow reactors. Soil Remediation : 15% focused on rhizosphere engineering, though field trials remain sparse (Rebello et al., 2021). Scale-Up Challenges Pilot Systems : Only 8% progressed beyond lab scale, citing regulatory hurdles and ecological risk concerns. Bioreactor Integration : 11% immobilized engineered microbes on alginate or biochar carriers, enhancing operational stability to 5+ cycles (Xue et al., 2024). 3.7 Performance and Efficacy Quantitative Outcomes Removal Efficiency : Engineered systems outperformed wild-type strains by 1.5–3x, e.g., Aspergillus niger with chromate reductase removed 92% Cr(VI) vs. 62% in wild types1. Tolerance Thresholds : Metal LC₅₀ values increased 2 to 4× post-engineering, e.g., E. coli surviving 2 mM Cu²⁺ via RcnA efflux pump overexpression1. Multi-Metal Capacity : Synthetic consortia achieved 70–80% co-removal of Pb/Cd/As in e-waste leachates, though with reduced kinetics vs. single-metal systems1. Limitations Field Viability : Only 6% conducted in-situ trials, citing concerns about horizontal gene transfer and competition with native microbiota1. Resource Demand : High-cost media (e.g., IPTG induction) limited scalability in 14% of studies, prompting shifts to autoinduction systems. 4. Discussion 4.1 Overview of Principal Findings This scoping review maps a decade of activity in the genetic and synthetic biological enhancement of microbial and algal systems for heavy‑metal remediation. Publication volume increased markedly after 2020 (81.2% of included studies), reflecting both methodological maturation and mounting regulatory and environmental pressure. The literature is dominated by bacterial chassis (bacteria present in ~90% of studies), with microalgae and fungi represented far less frequently, and genuinely integrative multi‑kingdom designs remaining uncommon (21.7% multi‑category; 17.4% involving all three groups). Mechanistically, most interventions combine one or more sequestration processes (bioaccumulation, adsorption, chelation) with enzymatic transformation (redox conversion or precipitation). Advanced control layers (biosensing, extracellular electron transfer optimisation, compartmentalization) appear only sporadically. Multi‑metal examination is the norm (60.9%), but incomplete enumeration in a minority of papers limits robust metal‑specific comparative analysis. Reported performance uplifts (roughly 1.5–3‑fold increases in removal efficiency and 2–4‑fold tolerance gains) are encouraging, yet translation beyond bench scale remains modest (8% pilot, 6% in situ). 4.2 Relation to Broader Synthetic Biology Trends Core engineering approaches still centre on plasmid‑based overexpression, metabolic pathway augmentation, and classical resistance determinants. More programmable, layered control architectures such as tightly coupled sensor–effector circuits, logic gating, or systematic CRISPR-mediated regulatory modulation are reported far less often than in other synthetic biology domains (e.g. metabolic manufacturing or therapeutic circuit design). The field therefore exhibits breadth of component use but limited integration into adaptive, closed‑loop systems. Under‑reporting, rather than true absence, may partially account for the conservative frequencies recorded (e.g. many studies likely used standard expression vectors without detailing them sufficiently for categorical coding). 4.3 Chassis Selection: Scope and Gaps Reliance on E. coli and P. putida is understandable given genetic tractability, yet over‑dependence on a narrow set of laboratory strains may limit ecological resilience, stress tolerance, and regulator comfort with environmental release. Indigenous extremophiles, rhizosphere‑associated bacteria, phototrophic microalgae, and engineered fungal partners are comparatively underexplored despite potential advantages in site‑specific persistence, energy autonomy (light capture), or substrate tolerance. A more deliberate diversification strategy supported by the development of reliable editing toolkits for non‑model organisms—could improve the ecological suitability and regulatory acceptability of candidate strains. 4.4 Mechanistic Architecture: From Accumulation to Integrated Function Most studies layer mechanisms additively (e.g. transporter overexpression plus a reductase enzyme) rather than designing spatially or temporally coordinated modules (e.g. sensing‑driven induction of reductive pathways only when intracellular burden thresholds are exceeded). Surface display strategies and engineered biofilm or amyloid matrices which can increase local binding site density and promote co‑localisation of catalytic functions remain rare. Similarly, extracellular electron transfer (EET) optimisation to accelerate redox transformations is still a minority focus, even though improved electron flux can materially enhance the kinetics of valence changes (e.g. Cr (VI) reduction). There is clear conceptual room to move from simple aggregation of components toward purposeful architectural coupling. 4.5 Reporting Quality and Data Completeness Three recurrent reporting limitations constrained deeper quantitative synthesis: (i) use of generic “heavy metals” descriptors without full elemental lists; (ii) mechanistic labels such as “detoxification” or “tolerance” without specifying underlying biochemical levers (e.g. efflux modulation vs thiol pathway expansion); and (iii) heterogeneous performance metrics (initial concentrations, contact times, pH, induction regimes) that resist normalization. A minimal reporting standard—explicit enumeration of metals (including oxidation state), defined initial and residual concentrations with exposure time, concise genetic construct description (vector, promoter, key genes), and controlled mechanism vocabulary would substantially enhance comparability and downstream meta‑analytical potential. 4.6 Scale‑Up and Translational Constraints Progress beyond laboratory settings is limited. Principal obstacles include regulatory uncertainty surrounding environmental deployment of genetically modified microorganisms, operational costs associated with inducers and rich media, and insufficient evidence for long‑term genetic stability or ecological persistence. Few studies report iterative reuse cycles, performance under variable field‑like physicochemical conditions (pH, salinity, organic co‑contaminants), or cost projections relative to physico‑chemical benchmarks. Addressing these gaps will require standardised mesocosm studies, medium cost optimisation (e.g. inducer‑free expression systems), and incorporation of life‑cycle and preliminary techno‑economic analyses earlier in the research pipeline. 4.7 Biosafety and Governance Considerations Explicit incorporation of biocontainment or biosecurity features (e.g. kill switches, conditional auxotrophy, dependency circuits) is strikingly rare. Given public and regulatory sensitivity, the absence of well‑documented containment strategies may delay approval processes and erode stakeholder confidence. Similarly, deliberate harnessing of horizontal gene transfer mechanisms appears only sporadically and raises additional risk considerations. Systematic evaluation of containment efficacy (escape frequency, stability of safeguards) should become a routine element of prototype characterisation rather than an afterthought. 4.8 Interpreting Reported Performance Gains Increases in removal efficiency and tolerance are meaningful but often reported without a common baseline. Improvements are typically attributed to single interventions (e.g. metallothionein expression, transporter modulation) without clarifying cumulative contributions in multi‑component constructs. Moreover, emphasis remains on maximal percentage removal rather than durability (number of cycles before performance decay), selectivity (target vs non‑target uptake), or energy/material intensity. Aligning performance reporting with metrics of practical relevance such as stability half‑life, selectivity ratios, volumetric throughput, and cost per unit metal removed would strengthen translational assessment. 4.9 Methodological Considerations As a scoping review, this study prioritised breadth over critical appraisal and effect size estimation. Single‑reviewer screening and conservative coding (not extrapolating implicit strategies from generic phrases) may understate the true prevalence of some techniques. Heterogeneity in design and outcome reporting precluded meta‑analysis. These constraints are characteristic of scoping methodology but should be acknowledged to avoid over‑interpretation of proportional counts as definitive prevalence estimates. 4.10 Future Research Priorities Several focused workstreams emerge: Integrated Control Systems: Develop and evaluate sensor–logic–effector circuits that modulate metal uptake and transformation dynamically rather than constitutively. Chassis Diversification: Expand editing tools and stability studies for extremophiles, plant‑associated strains, and phototrophic hosts suited to specific contaminated matrices. Standardised Reporting: Adopt a concise, community‑endorsed template for metals addressed, construct architecture, mechanism tags, and performance metrics. Containment by Design: Embed and quantitatively validate genetic and process-level containment strategies early in prototype development. Mechanism Coupling: Explore spatial (compartmentalization, biofilm patterning) and electrochemical (EET enhancement) design to coordinate sequestration with transformation kinetics. Economic and Environmental Assessment: Integrate preliminary cost and life‑cycle analyses to prioritise constructs with plausible field viability. Field‑Relevant Stress Testing: Systematically assess performance under fluctuating pH, salinity, mixed metal/organic burdens, and competitive native microbiota. Data Infrastructure: Establish open repositories for standardized genetic parts and validated performance datasets to reduce duplication and accelerate comparative evaluation. 4.11 Implications for Stakeholders Researchers should emphasise transparent, standardised construct and mechanism reporting and incorporate multi‑dimensional performance metrics (capacity, stability, selectivity, containment). Industry partners can facilitate translation by supporting pilot platforms and insisting on validated containment prior to co‑development or licensing. Regulators may consider structured sandbox trials with pre‑defined monitoring to gather environmental safety data under controlled conditions. Funders and investors should scrutinise proposals for credible scale‑up pathways, containment provisions, and life‑cycle performance indicators, not just laboratory removal percentages. 4.12 Limitations of This Review and Mitigation Opportunities The reliance on two databases, exclusion of non‑English and grey literature, and single‑reviewer extraction limit comprehensiveness and may introduce selection bias. Conservative categorisation likely underestimates widely used baseline engineering practices. Future systematic efforts could broaden database coverage, employ dual independent screening, and harmonise outcomes to enable effect size modelling (e.g. standardized removal per unit biomass per unit time). Inclusion of unpublished pilot datasets under appropriate confidentiality could reduce publication bias and sharpen translational insights. 4.13 Conclusions Genetic and synthetic biology interventions have demonstrably improved microbial and algal heavy‑metal remediation performance, but most published efforts remain laboratory‑centred and component‑focused. Consolidation around a small set of bacterial chassis, limited deployment of adaptive regulatory circuits, and sparse incorporation of containment or spatially structured strategies highlight a maturing yet incomplete innovation profile. Advancing toward practical environmental deployment will depend on integrated control architectures, diversified and context‑appropriate hosts, rigorous biosafety measures, standardised reporting, and early techno‑economic contextualisation. Addressing these priorities should accelerate responsible translation of engineered biological systems into reliable tools for mitigating persistent heavy‑metal contamination. Declarations 5. Ethics and Dissemination Ethics approval was not required for this scoping review as it did not involve human or animal subjects. Findings will be disseminated through peer-reviewed journal publication and presentations at scientific conferences. Stakeholders in environmental biotechnology, policy, and industry will be targeted for knowledge translation. 6. Funding This research was self-funded by the author. 7. Statements and Declarations The author declares no conflicts of interest related to this work. 8. Acknowledgements The author would like to thank all researchers whose work contributed to the included studies. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7175786","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":488445979,"identity":"580f3e2a-328d-4698-8ca8-dc01a193461c","order_by":0,"name":"Kartik Tiwary","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAABBUlEQVRIie2SsWrDMBCGJVI6CbrapOQZrhREB2M/SJcLBnkq9AEyqFPGrnmJrp0FhnRxqlWli7Koq7tlyFBJ7dDFdsZC9Q2HDu7jvwMRkkj8QbJQUBEWO4TCV/qgJhQqUcG3Yu9FUOS0QhTEhtq+jY9RJV/vPqztjpfwsnMZgi6f1q1PWRW3Q8qcNVcSDTDoGu6V9/q5W3plK+7kgLIgwt/SA+NKnEeFK69Q2Q4rF+5H0S4orzXX+3FlnoUUvxg3MUWV3Eyk5BtHN9hds8q42Q1Cjdz4FBy5JdOCfB62iyp/FPTtcCwrrpu97VfFoPKbs/AVlnESTxgPzHpfqhOHE4lE4h/xBUIaZmxevD/tAAAAAElFTkSuQmCC","orcid":"","institution":"","correspondingAuthor":true,"prefix":"","firstName":"Kartik","middleName":"","lastName":"Tiwary","suffix":""}],"badges":[],"createdAt":"2025-07-21 09:38:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7175786/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7175786/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":87281281,"identity":"84acfc52-c649-44b5-b594-fcd5e0384e13","added_by":"auto","created_at":"2025-07-22 09:40:11","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":286349,"visible":true,"origin":"","legend":"\u003cp\u003eFlowchart of the review search strategy\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7175786/v1/0b91c8adfd4a544823d4177e.jpeg"},{"id":87403145,"identity":"a5c1e761-b61c-426e-aac0-fbf655c53e7b","added_by":"auto","created_at":"2025-07-23 12:17:02","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4103297,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7175786/v1/7d9722ed-ed72-43c7-8468-11f2a9382d54.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Synthetic Biology and Genetic Engineering Strategies for Microbial and Algal Bioremediation of Heavy Metals: A Scoping Review","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eHeavy metal pollution, particularly from mining, electroplating, e-waste processing, and agrochemical runoff, remains a pressing environmental and public health issue worldwide. Chronic exposure to toxic metals such as cadmium (Cd), arsenic (As), lead (Pb), chromium (Cr), and mercury (Hg) has been linked to neurotoxicity, carcinogenesis, soil infertility, and biodiversity loss (Igiri et al., \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2018\u003c/span\u003e). Conventional remediation approaches, including chemical precipitation, ion exchange, and membrane filtration often suffer from high operational costs, incomplete removal at low concentrations, and the generation of hazardous secondary wastes (Verma and Kuila, \u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). This has prompted a shift toward more ecologically viable alternatives such as microbial bioremediation.\u003c/p\u003e\u003cp\u003eMicrobial systems, especially bacteria, fungi, and microalgae have demonstrated inherent capabilities to adsorb, transform, or volatilize heavy metals through natural metabolic pathways (Liu et al., \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e2019\u003c/span\u003e). However, wild-type microbes often exhibit low tolerance thresholds, limited specificity, and poor adaptability under harsh environmental conditions (Capeness and Horsfall, \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2020\u003c/span\u003e). Recent advances in synthetic biology and genetic engineering have enabled the development of tailor-made microbial strains with enhanced metal-binding affinity, transporter overexpression, and programmable sensing-response behaviors (Tran et al., \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eEngineered systems have incorporated modular components such as metallothioneins, phytochelatin synthases, sulfur-assimilation operons, and CRISPR-regulated biosensors to enable dynamic and targeted remediation of metal ions (Liu et al., \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Widely used model organisms such as \u003cem\u003eE. coli\u003c/em\u003e, \u003cem\u003eShewanella oneidensis\u003c/em\u003e, \u003cem\u003ePseudomonas putida\u003c/em\u003e, and \u003cem\u003eChlamydomonas reinhardtii\u003c/em\u003e have been genetically reprogrammed for enhanced tolerance and accumulation of Cr (VI), Cd (II), As (III), Cu (II), and other priority metals (Cui et al., \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e\u003cp\u003eDespite the growing body of literature, no consolidated framework currently maps and evaluates these synthetic biology-driven microbial platforms in terms of chassis selection, engineered features, target metals, and application scenarios (Sattayawat et al., \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2021\u003c/span\u003e). Therefore, this scoping review aims to systematically chart the landscape of microbial systems genetically modified for heavy metal bioremediation. The study provides a thematic synthesis of engineered features, synthetic toolkits, deployment environments, and research gaps, with the objective of guiding future design strategies and translational efforts (Giachino et al., \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2020\u003c/span\u003e).\u003c/p\u003e"},{"header":"2. Objective","content":"\u003cp\u003eThe objective of this scoping review is to systematically map and synthesise the landscape of genetically engineered microbial systems for heavy metal bioremediation, focusing on: Microbial hosts and chassis selection, engineered features and synthetic toolkits, Target heavy metals, Remediation mechanisms, Application environments, Key research gaps and recommendations\u003c/p\u003e"},{"header":"3. Materials and Methods","content":"\u003cp\u003e\u003cstrong\u003e3.1 Study Design and Objective\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA scoping review methodology was employed to systematically map and synthesize research on genetically engineered and synthetic biology - enabled microbial bioremediation of toxic heavy metals. The primary objective was to identify and characterize (i) microbial chassis employed, (ii) engineered genetic or synthetic biology constructs, (iii) targeted metal species, (iv) mechanistic remediation pathways, and (v) application contexts. The review followed PRISMA‑ScR guidance to enhance transparency and reproducibility (Tricco et al., 2018). A formal protocol was not prospectively registered.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Data Sources and Search Strategy\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTwo bibliographic databases (Scopus and PubMed) were searched for articles published between 1 January 2015 and 31 May 2025. The core Boolean strategy combined three conceptual domains (engineering/synthetic biology, bioremediation processes, and heavy metals):(\u0026quot;synthetic biology\u0026quot; OR \u0026quot;genetic engineering\u0026quot; OR \u0026quot;recombinant DNA\u0026quot; OR \u0026quot;engineered microbes\u0026quot;) AND (\u0026quot;bioremediation\u0026quot; OR \u0026quot;biosorption\u0026quot; OR \u0026quot;bioaccumulation\u0026quot;) AND (\u0026quot;heavy metals\u0026quot; OR \u0026quot;lead\u0026quot; OR \u0026quot;cadmium\u0026quot; OR \u0026quot;arsenic\u0026quot; OR \u0026quot;chromium\u0026quot; OR \u0026quot;mercury\u0026quot;)\u003cstrong\u003e. \u003cbr\u003e \u003cbr\u003e \u003c/strong\u003eSearches were restricted to English‑language, peer‑reviewed journal articles. Conference abstracts, theses, book chapters, patents, and other gray literature were excluded. Records were exported to Rayyan for centralized deduplication and screening.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.3 Eligibility Criteria\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eInclusion criteria:\u003c/strong\u003e Studies that (1) described microbial (bacterial, fungal, or microalgal) bioremediation interventions involving synthetic biology or genetic engineering (e.g., heterologous gene expression, genome editing, modular circuits); (2) targeted one or more toxic heavy metals (Cd, Pb, Cr\u0026mdash;speciation noted when reported, As, Hg, Cu, Ni, Zn); (3) reported experimental data \u003cem\u003eor\u003c/em\u003e provided mechanistically substantive conceptual innovations directly tied to engineering strategies; and (4) were published within the defined date range in English.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eExclusion criteria:\u003c/strong\u003e (1) Interventions using only wild‑type strains without genetic/synthetic modification; (2) studies focused exclusively on non‑metal pollutants; (3) insufficient mechanistic or engineering detail (e.g., general environmental commentary); (4) conventional review articles lacking new analytical or mechanistic framing specific to engineered systems; (5) publications outside the temporal or language limits.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.4 Study Selection and Screening Process\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll titles and abstracts were screened in Rayyan. Of 941 retrieved records, 30 duplicates were removed (911 unique). Title/abstract screening excluded 838 records. Seventy‑three full texts were assessed; four were excluded for absence of qualifying synthetic biology or genetic engineering methodology, yielding 69 included studies. Reasons for full‑text exclusion were logged. The study selection flow is depicted in Figure 1. Screening and selection were conducted by a single reviewer; consistency was supported by predefined criteria, but this introduces potential subjective bias (acknowledged in Limitations).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.5 Data Charting and Extraction\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData extraction was performed manually in Microsoft Excel using an iteratively refined charting framework. Extracted variables comprised: bibliographic data (title, year), microbial host(s)/chassis, targeted heavy metal(s), genetic/synthetic constructs (e.g., expression systems, CRISPR edits, biosensors, metabolic rewiring), remediation mechanism(s), application context (e.g., wastewater, soil, simulated effluent), key performance indicators (e.g., removal efficiency, tolerance), and stated limitations or translational constraints. The coding scheme was expanded inductively as new patterns emerged, preserving an audit trail of added categories.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eChassis coding:\u003c/strong\u003e Each study was first coded for presence (yes/no) of engineered bacterial, microalgal, and fungal chassis. For mutually exclusive reporting, studies were assigned to one of four categories: \u003cem\u003eonly bacteria\u003c/em\u003e, \u003cem\u003eonly microalgae\u003c/em\u003e, \u003cem\u003eonly fungi\u003c/em\u003e, or \u003cem\u003emulti‑category\u003c/em\u003e (\u0026ge;2 chassis types present). Studies employing multiple bacterial species without other microbial types were classified as \u003cem\u003eonly bacteria\u003c/em\u003e. Multi‑category studies were sub‑typed (all three vs dual combinations). Presence (non‑exclusive) tallies exceed mutually exclusive totals because multi‑category studies contribute to multiple chassis types.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMetal target coding:\u003c/strong\u003e Metal targeting was coded as \u003cem\u003esingle‑metal specified\u003c/em\u003e (exactly one experimentally assayed metal named), \u003cem\u003emulti‑metal specified\u003c/em\u003e (\u0026ge;2 named metals assayed), or \u003cem\u003eunspecified\u003c/em\u003e (references to \u0026ldquo;heavy metals\u0026rdquo; without enumeration). Single‑metal tallies by element are reported. Comprehensive cross‑study element prevalence was not derived to avoid speculative inflation given overlapping multi‑metal sets and a subset of unspecified reports. Mentions of metals solely in contextual/background text, without corresponding experimental assays, were not counted as targets.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMechanism classification:\u003c/strong\u003e Mechanisms were categorized based on explicit experimental or engineered functional claims into biosorption (surface binding/exopolymers), bioaccumulation (transporter-mediated intracellular sequestration/chelation), enzymatic redox transformation (reductases/oxidases altering valence state), biomineralization/precipitation (including nanoparticle formation), compartmentalization (e.g., encapsulins, organelle mimetics), and integrated or hybrid modalities (e.g., bioelectrochemical coupling). Studies could map to multiple mechanism categories.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eApplication context coding:\u003c/strong\u003e Deployment contexts were coded as laboratory (bench scale), simulated matrix (e.g., synthetic wastewater, spiked soil microcosms), pilot (scaled continuous or semi‑continuous system, defined operational period), or field (in situ environmental site). Immobilization carriers (e.g., alginate, biochar) and consortial configurations were flagged as binary attributes.\u003c/p\u003e\n\u003cp\u003eNo formal critical appraisal (risk‑of‑bias or quality scoring) was undertaken, consistent with scoping review methodology focused on breadth of coverage rather than evidence grading.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.6 Synthesis of Results\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGiven heterogeneity in study objectives, experimental designs, host organisms, genetic constructs, metrics, and reporting formats, a qualitative thematic synthesis was performed. Quantitative descriptors (counts and percentages) were generated for categorical variables (chassis categories, metal target scope, mechanism classes, application contexts) using the study as the unit of analysis, with explicit notation where categories were non‑exclusive. Findings are presented across five analytical dimensions: (1) microbial chassis distribution, (2) heavy metal target scope, (3) genetic and synthetic engineering strategies, (4) remediation mechanisms, and (5) application environments and progression toward scale. Inferential statistical pooling (e.g., meta‑analysis) was not attempted due to incomparable outcome measures and heterogeneous performance metrics.\u003c/p\u003e\u003cp\u003e\u003cstrong\u003eTable 1\u0026nbsp;\u003c/strong\u003eSummary of the information extracted from the included studies (This table was created by the author based on data extracted during the review.)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"718\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bioremediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eEngineering Aspergillus niger for Effective Bioremoval of Hexavalent Chromium from Water\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eXie et al., (2024)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eAspergillus niger\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCr (VI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eOverexpression of chrR, chrP, and sodA genes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eChromate uptake, reduction, and ROS detoxification\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetically engineered A. niger showed 92% improved Cr(VI) removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eLab-scale strain engineering without field validation, scalability, multi-metal tolerance, or stability assessment.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eHarnessing microbes for heavy metal remediation: mechanisms and prospects\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eDeo, Osborne and Benjamin, (2024)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious bacteria, fungi, and algae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eGenetic engineering and nano-technology\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eBioaccumulation, biosorption, biomineralization, redox reactions\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEmphasizes prospects and recent advancements using omics and engineered microbes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eLacks empirical validation and quantified strain performance; broad synthesis without in-depth data.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eMicrobial strategies for lead remediation in agricultural soils and wastewater\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGul et al., (2024)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBacteria, fungi, microalgae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eLead (Pb)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eGenetic engineering techniques mentioned\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eBiosorption, bioprecipitation, biomineralization, bioaccumulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eHighlights microbial detoxification pathways and Pb nanoparticle formation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eGenetic strategies unvalidated; no rhizosphere testing or lead-specific synthetic framework.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eArsenic bioremediation in mining wastewater by controllable genetically modified bacteria with biochar\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eXue et al., (2024)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eE. coli (genetically modified)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eArsenic (As)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eGenetic modification of arsenic detoxification pathway\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eBioadsorption with biochar enhancement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eControllable expression improved arsenic removal and stability with biochar\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003ePilot-scale only; lacks long-term survival, ecological impact data, and cross-contaminant applicability.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eThe Utility of Synthetic Biology in the Treatment of Industrial Wastewaters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eJoshi and Sharma, (2025)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eNo specific bacterial species\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eNo specific heavy metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eSynthetic operons, modular genetic circuits\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eEngineered biosensors and effector modules\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynthetic biology designs for precision wastewater remediation.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eLacks mechanistic detail, field-scale evidence, and experimental validation.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eAdvances in actinobacteriabased bio-remediation: mechanistic insights, genetic regulation, and emerging technologies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMakarani and Kaushal, (2025)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eActinobacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eGenetic engineering and omics-based optimization\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eRedox modulation, biosorption, siderophore production\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eOmics-guided genetic regulation enhances metal detoxification\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eSpeculative mechanisms; no synthetic circuit data or cross-strain/metal performance metrics.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"709\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003ePotential applications of extremophilic bacteria in the bioremediation of extreme environments contaminated with heavy metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSun et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eExtremophilic bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCr, Cd, As, Pb, Hg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetic adaptation and resistance plasmids\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eTolerance mechanism, biosorption\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eEngineered extremophiles enhance metal resistance and bioaccumulation.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eLimited case studies; theoretical focus without real-world application or metabolic burden data.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eInnovative Approaches in Extremophile-Mediated Remediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSwaminaathan et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eExtremophiles\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eOmics and synthetic constructs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMultifunctional enzyme systems, bioaccumulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eAdvanced strategies combine genetic tools with extremophilic resilience\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eConceptual focus without empirical results or experimental evidence.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eEquilibrium, kinetic, and thermodynamic studies on the biosorption of lead by human metallothionein gene-cloned bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eAkkurt et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eLead (Pb)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eCloning of human metallo-thionein gene\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBiosorption\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eEngineered strain shows high biosorption efficiency fitting Langmuir model.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eSorption-focused; lacks long-term application data and genetic stability analysis.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eEnhancing efficacy of microbial bioremediation by intervention of nanotechnology and metabolic engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMehta et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious microbes (bacteria, fungi)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMetabolic engineering, nano-bioconjugates\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBiosorption, intracellular chelation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eCombining nanotech with engineered pathways increases metal selectivity and uptake\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eConceptual; no strain-specific cases or application validation.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eConstruction of Genetically Engineered Escherichia coli Cell Factory for Enhanced Cadmium Bioaccumulation in Wastewater\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eTian et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCadmium (Cd)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetically engineered expression systems for cadmium-binding\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBioaccumulation via cell surface engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eEnhanced Cd bioaccumulation via engineered E. coli increases remediation efficiency\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eLab-scale only; no environmental safety or long-term genetic stability data.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eComprehensive approaches to heavy metal bioremediation: Integrating microbial insights and genetic innovations\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ekhan et al., (2025)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMultiple bacterial species\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, Hg, As\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eCRISPR, recombinant protein expression\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMulti-pathway detoxification and biosorption\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eIntegration of microbial mechanisms and genetic engineering enhances metal specificity and resilience\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eConceptual without empirical validation or specific experimental outcomes.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"718\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eGenetic Adaptations and Mechanistic Insights Into Bacterial Bioremediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eVinayagam and Rajeswari, (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eDiverse environmental bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eGenomic analysis and bio-engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eEnzymatic detoxification, efflux systems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eHighlights bacterial adaptations and gene targets for improved metal tolerance\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eDescribes evolutionary adaptations; lacks synthetic biology implementation.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eStrategies for cadmium remediation in nature and their manipulation by molecular techniques: a comprehensive review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eIqbal et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious, bacteria, fungi and microalgae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u0026nbsp;Cd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eGene over-expression and recombinant plasmids\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eAdsorption and biotransformation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eOptimized genetic interventions enhance Cd remediation across hosts.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eTheoretical model without synthetic validation or scalability assessment.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBiofilm-mediated bioremediation of xenobiotics and heavy metals: a comprehensive review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSarkar and Bhattacharjee, (2025)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBiofilm-forming microbes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003ePb, Cr, Hg, As\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSynthetic biology to modulate biofilm properties\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eBiofilm-mediated absorption and reduction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eEngineered biofilms show enhanced resistance and bioremediation capacity\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eEcological focus; minimal synthetic detail; no reproducible performance metrics\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eA comprehensive review on effective removal of toxic heavy metals from water using genetically modified micro-organisms\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eFatima et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetically modified micro-organisms including \u003cem\u003eE. coli, Pseudomonas, and Bacillus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eTransgenic modification and protein engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eActive transport and intracellular binding\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eGM strains outperform wild types in pollutant binding and removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eReview-only; no lab/field data or insights on gene stability and ecological risks.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eThe arsenic bioremediation using genetically engineered microbial strains on aquatic environments\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eNaiel et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetically modified bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u0026nbsp;As\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eOver-expression of As resistance genes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eTransformation and bioaccumulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eArsenic detoxification enhanced via upregulated metabolic pathways\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eAs-specific; lacks in situ viability under mixed contaminants or stressors.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eHorizon scanning of potential environmental applications of genetically modified microorganisms\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eMiklau et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious (GMOs including microalgae, bacteria and fungi)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eNext-gen sequencing and genetic editing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eBiosensors, metal-binding peptides\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eExplores future prospects and biosafety of GMOs in metal bioremediation.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eHorizon scanning without experimental validation or mechanistic confirmation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003ePerspective Evaluation of Synthetic Biology Approaches for Effective Mitigation of Heavy Metal Pollution\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eMishra et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynthetic microbes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eHg, As, Pb, Cu, Cd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eDBTL cycle, biosensors, synthetic operons\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eSurface display\u0026ndash;mediated biosorption; Metabolic chelation \u0026amp; transporter engineering for bioaccumulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eSynthetic biology enables precision remediation using tailored microbial chassis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eLacks microbial models; abstract without concrete strain development data.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eEncapsulins from Ca. Brocadia fulgida: An effective tool to enhance the tolerance of engineered bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eWang et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eE. coli\u003c/em\u003e expressing \u003cem\u003eBrocadia fulgida\u003c/em\u003e encapsulin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eZinc (Zn)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eEncapsulin expression vector (pET-28a-cEnc)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eSequestration and tolerance enhancement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eEncapsulin enhances Zn tolerance via novel compartmentalization.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eZn\u0026sup2;⁺ focused; no cross-metal assessment or real-world application data.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"718\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eCurrent Eco-friendly and Sustainable Methods for Heavy Metals Remediation of Contaminated Soil and Water\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eYadav and Sharma, (2023)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious (Bacteria, fungi and algae)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCd, Cu, Hg, Pb, Mn, Ni, Zn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetic engineering, nanobiotechnology\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eBiosorption, bio-accumulation, phyto-remediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eIntegrates genetic engineering and nanotechnology for metal remediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eTheoretical; no experimental data, field validation, or gene editing insights.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eTrends in Bioremediation of Heavy Metal Contaminations\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eJeyakumar et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBacteria, fungi, algae, genetically altered microorganisms\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCr, Pb, Hg, Cd, Ni, Co\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetic modification\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eDetoxification, biosorption, bio-accumulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eOutlines microbial and genetic strategies for bioremediation.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eBroad, minimal synthetic detail; no case studies or quantitative data.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eEngineered bacterium-binding protein promotes root recruitment of functional bacteria for enhanced cadmium removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eFeng et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eCupriavidus taiwanensis, Pseudomonas putida\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCadmium (Cd)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEngineered protein (LcGC)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eEnhanced root recruitment and colonization via protein-bacterial contact\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eLcGC protein boosts phyto-remediation with up to 96% Cd removal.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eNeeds field validation; limited scalability; genetic control specificity unexamined.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eGenetic engineering to enhance microalgal-based produced water treatment with emphasis on CRISPR/Cas9: A review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eHassanien et al., (2023)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetically modified microalgae (e.g., Chlamydomonas, Scenedesmus)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eCRISPR/Cas9, genome editing tools\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eMetal uptake enhancement, biosorption, enzymatic reduction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eCRISPR boosts microalgal efficiency in metal removal from effluents.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eEarly-stage; few metal-specific cases; no real-world performance data.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eMercury bioremediation by engineered Pseudomonas putida KT2440 with adaptationally optimized biosecurity circuit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eXue et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003ePseudomonas putida KT2440\u003c/em\u003e (engineered)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eMercury (Hg)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBiosecurity circuit with CRISPR optimization\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eHg reduction to less toxic forms and sequestration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eEngineered \u003cem\u003eP. putida\u003c/em\u003e achieves 90% Hg removal with improved safety in lab conditions.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eHg\u0026sup2;⁺-specific; limited generalizability; synthetic circuit complexity limits scalability.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eEngineered microbes as effective tools for the remediation of polyaromatic hydrocarbons and heavy metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eSharma et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious bacteria, fungi and algae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCd, Pb, As, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynthetic gene constructs, operon regulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eSimultaneous degradation and heavy metal sequestration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eCo-remediation potential using engineered microbes highlighted for multi-pollutant waste\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003eMost findings are in vitro; lacks ecosystem interaction studies and real-world deployment data.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"699\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eEngineering microbes for enhancing the degradation of environmental pollutants: A detailed review on synthetic biology\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eYaashikaa, Devi and Kumar, (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetically engineered bacteria, cyanobacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eMultiple (not specified)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eCRISPR, synthetic operons, modular chassis\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePathway modification for detoxification and resistance\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eSynthetic biology drives pollutant-specific pathway enhancement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eReview-based with limited experiments; broad focus lacks heavy metal specificity.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBioremediation techniques for heavy metal and metalloid removal from polluted lands: A review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eOjha et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious bacteria and fungi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eAs, Cd, Pb, Cr, Zn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eTransgenic manipulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMicrobial chelation, transformation and efflux\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eDetails microbial remediation mechanisms for land cleanup.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eReview-focused; lacks depth on gene expression systems and molecular techniques\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eMicrobial Remediation: A Promising Tool for Reclamation of Contaminated Sites with Special Emphasis on Heavy Metal and Pesticide Pollution\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eTarfeen et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious bacteria, fungi, microalgae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003ePb, Cd, Hg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGene over-expression and horizontal gene transfer\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMicrobial metabolism, transformation of metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eSupports engineered bio-remediation across pollutants.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eGeneralized; no quantitative data or synthetic construct validation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eMicrobial Interventions in Bioremediation of Heavy Metal Contaminants in Agroecosystem\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003ePande et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSoil microbial consortia (modified and natural)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eAs, Cd, Zn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenomic optimization (descriptive)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEnzymatic conversion and microbe-metal interactions\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eProposes optimized engineered consortia for soil cleanup\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eEmphasizes native strains; synthetic biology remains conceptual\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eRemoval of toxic heavy metals using genetically engineered microbes: Molecular tools, risk assessment and management strategies\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSaravanan et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetically engineered \u003cem\u003eEscherichia coli, Pseudomonas spp.\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, Hg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eRecombinant plasmids, CRISPR/Cas systems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBiosorption, enzymatic detoxification\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eMolecular tools enable selective, efficient metal removal.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eEnvironmental instability, HGT risk, stress sensitivity, and regulatory barriers.\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBiological and green remediation of heavy metal contaminated water and soils: A state-of-the-art review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSarker et al., (2023)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious bacteria, fungi and microalage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eAs, Pb, Cd, Zn, Ni\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGene transfer and metabolic pathway enhancement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBio-accumulation, precipitation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eIntegrates traditional bio-remediation with genetic advances.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eSlow kinetics, specificity limits, soil variability, and complex regulation\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"699\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eA critical review on microbes-based treatment strategies for mitigation of toxic pollutants\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSharma et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eVarious bacteria, fungi and algae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCr, Pb, Hg, As\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eOver-expression of resistance genes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMicrobial detoxification and biosorption\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMicrobial strategies can be enhanced by synthetic biology approaches\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLacks field optimization and engineered system validation; theoretical only\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eReview of microbial biosensor for the detection of mercury in water\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eBose, Maity and Sarkar, (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eGenetically engineered Escherichia coli\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eHg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetic reporter circuits\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eReal-time detection using gene-based biosensors\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynthetic circuits enable accurate and selective Hg detection\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDiagnostic focus; no remediation; hindered by co-contaminants\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eStrategies for microbial bioremediation of environmental pollutants from industrial wastewater: A sustainable approach\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSaravanan et al., (2023)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eEngineered bacterial consortia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eMultiple (Cd, Pb, Cr)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenomic editing and metabolic engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynergistic pollutant removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynthetic microbial communities show improved detoxification potential\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRelies on unstable microbial interactions; hard to scale in effluents\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eConstruction and characterization of an engineered recombinant \u003cem\u003eRhodopseudomonas palustris\u003c/em\u003e to remove Cd2+, Zn2+ and Cu2+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eJia et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cem\u003eRhodopseudomonas palustris (engineered)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCd, Zn, Cu\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eCloning of metal resistance genes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eActive transport and sequestration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEngineered strain shows significantly improved uptake of target metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEffective only in labs; high metabolic load; no field data\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eGenetically engineered microbial remediation of soils co-contaminated by heavy metals and polycyclic aromatic hydrocarbons\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eWu et al., (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eEngineered bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCd, Pb, Hg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePlasmid expression systems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSimultaneous detoxification of metals and organics\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eDemonstrates feasibility of dual remediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEcological risks, instability, HGT, regulation issues, poor scalability\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eSynthetic biology approaches to copper remediation: Bioleaching, accumulation and recycling\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eGiachino et al., (2020)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eEngineered bacterial strains\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCopper (Cu)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynthetic metabolic pathways\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eRedox cycling and bioleaching\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynthetic pathways enable scalable copper recovery\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLow viability in high-copper loads; no field or waste matrix optimization\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eSystematically assessing genetic strategies for engineering electroactive bacterium to promote bio-electrochemical performances and pollutant removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eLi et al., (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cem\u003eShewanella oneidensis (engineered)\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003ePb, Cd, Cu\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eCRISPR/Cas, gene knockout\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEnhanced metal-electron transfer coupling\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEngineered electro-active bacteria enhance remediation and energy generation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eElectroactive-specific; limited scalability; engineered trait stability untested\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"718\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bioremediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eMitigation of environmental pollution by genetically engineered bacteria- Current challenges and future perspectives\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eLiu et al., (2019)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious bacteria, fungi and alage\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Hg, Pb, As\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePathway engineering, chassis design\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eMetabolic and enzymatic detoxification\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOutlines roadmap for synthetic biology in bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGene silencing, plasmid loss, biosafety risks, no field data.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eSynthetically engineered microbial scavengers for enhanced bioremediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eTran et al., (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynthetic and natural bacterial consortia\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, Hg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePathway modularisation, chassis design\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eSurface display mediated biosorption; Metallothionein/peptide sequestration; Pathway rewiring for thiol-based chelation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSynthetic design boosts resilience and metal uptake specificity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEcological risks, gene transfer, lacks long-term field data\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eRemoval of Chromium (VI) by Escherichia coli Cells Expressing Cytoplasmic or Surface-Displayed ChrB: a Comparative Study\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eZhou et al., (2020)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCr(VI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eChrB expression\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eReduction and immobilization\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSurface display enhances Cr(VI) reduction efficiency\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimited scalability, stability; lab-focused performance only\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eEngineering Biocatalytic and Biosorptive Materials for Environmental Applications\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eZhu, Chen and Wei, (2019)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGenetically modified bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eHg, Pb, Cd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEnzyme display systems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eEnzymatic detoxification + biosorption\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBiocatalysis-sorption synergy improves remediation efficiency\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBiocatalyst recovery issues; unclear pathways in wastewater\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eToxicity and Bioremediation of Heavy Metals Contaminated Ecosystem from Tannery Wastewater: A Review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eIgiri et al., (2018)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eVarious microbes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCr, Pb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMetabolic pathway engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eMetal ion reduction and precipitation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eBioengineered microbes effectively reduce tannery pollution\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGeneral review; limited engineered focus and mechanistic detail\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eBioengineered microbes for soil health restoration: present status and future\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eRebello et al., (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEngineered rhizobacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, Zn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMetal transporter genes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eRhizosphere bioremediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eRoot-associated strains enhance metal bioavailability and uptake\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSoil variability, microbial survival, limited genetic control insights.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eDeciphering and engineering photosynthetic cyanobacteria for heavy metal bioremediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCui et al., (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEngineered cyanobacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eAs, Hg, Pb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePromoter tuning, synthetic circuits\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003ePhototrophic sequestration and detox\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eHarnesses light-driven mechanisms to optimize remediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePhotosynthetic efficiency under metal stress unresolved; transformation needs refinement.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 132px;\"\u003e\n \u003cp\u003eMetal and metal(loid) removal efficiency using genetically engineered microbes: Applications and challenges\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eSharma et al., (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia coli, Pseudomonas (engineered\u003c/em\u003e)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCr, Cu, Zn, Pb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eCRISPR-mediated pathway enhancement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eBio-accumulation, efflux control\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eDemonstrates scalable detox strategies with gene editing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHGT risk, operational control, and GEM regulatory hurdles persist\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"709\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBio-recovery of non-essential heavy metals by intra- and extracellular mechanisms in free-living microorganisms\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eGarc\u0026iacute;a-Garc\u0026iacute;a, S\u0026aacute;nchez-Thomas and Moreno-S\u0026aacute;nchez, (2016)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eWild-type and modified bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Hg, Pb\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eMetal-binding protein over-expression\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eIntracellular sequestration, extracellular chelation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eDual-mode removal pathways expand detox potential\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFocuses on natural mechanisms; minimal genetic engineering detail\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eTranscription profiling-guided remodeling of sulfur metabolism in synthetic bacteria for efficiently capturing heavy metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eLiu et al., (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSynthetic \u003cem\u003eEscherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Hg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eTranscriptional reprogramming\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSulfur-metal chelation enhancement\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eDemonstrates precision-engineered uptake via sulfur metabolism\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eOperon stability, scalability untested; limited to Pb and Cd\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eSynthetic Biology-Based Approaches for Microalgal Bio-Removal of Heavy Metals From Wastewater Effluents\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSattayawat et al., (2021)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eGenetically engineered microalgae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003ePb, Cr, As\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eMetabolic circuit rewiring\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEnhanced uptake and sequestration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eProves synthetic biology enables metal capture in algal systems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTheoretical, early-stage; lacks validation and performance data\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eEmerging investigator series: emerging biotechnologies in wastewater treatment: from biomolecular engineering to multiscale integration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eZhang et al., (2020)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eEngineered microbial systems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eVarious but none specific\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eBiomolecular engineering, biosensing elements\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBio-electro-chemical detection and remediation systems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMultiscale design improves detection-response coordination for pollutant removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eScalability uncertain; no pilot data; integration with treatment unaddressed\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eNanoscale Construction Biotechnology for Cementitious Materials: A Prospectus\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eChen et al., (2021)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eMicrobially induced calcite precipitation bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eNo specific\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eSynthetic pathway modulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eHeavy metal encapsulation during cementation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePotential environmental remediation through bio-cementing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMaterial-focused; lacks empirical evidence for synthetic bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBioremediation of heavy metals by microbial process\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eVerma and Kuila, (2019)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eVarious bacteria and fungi\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, Cr, Hg\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eNot focused\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMetal uptake, sequestration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eClassical mechanisms covered; no engineering tools detailed\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGeneral overview; limited engineered system and field efficacy detail\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"699\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBioremediation potential of Cd by transgenic yeast expressing a metallothionein gene from Populus trichocarpa\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eDe Oliveira et al., (2020)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eTransgenic \u003cem\u003eSaccharomyces cerevisiae\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eMetallothionein gene expression\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEnhanced Cd sequestration\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eTransgenic yeast increased Cd tolerance and uptake\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCd-focused; lacks stability, biosafety, and multi-metal capability.\u0026rdquo;\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eIs Genetic Engineering a Route to Enhance Microalgae-Mediated Bioremediation of Heavy Metal-Containing Effluents\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eRanjbar and Malcata, (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eEngineered microalgae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eAs, Pb, Cd\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eGene editing, metabolic optimization\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eBioaccumulation and detoxification\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSupports algal genetic engineering for remediation applications\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCRISPR/TALENs species-specific; poor transformation efficiency\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eSynthetic biology approaches towards the recycling of metals from the environment\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eCapeness and Horsfall, (2020)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eSynthetic microbes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCr, Cu, Pb, Zn\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eGenome-scale engineering, synthetic operons\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMetal sequestration, efflux, and precipitation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eOutlines synthetic biocircuit applications in environmental cleanup\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eConceptual; no validation or field-ready engineered strains\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBiotechnology Advances in Bioremediation of Arsenic: A Review\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003ePreetha et al., (2023)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eGenetically modified bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003ears operon engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eAs(V) reduction and As(III) volatilization\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eEngineered strains show enhanced arsenic remediation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReview-only; lacks synthetic biology integration and field strategy\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eUsing Fungi in Artificial Microbial Consortia to Solve Bioremediation Problems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eEfremenko et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eEngineered fungi and bacteria\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eFungal synthetic communities\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSynergistic metal uptake and breakdown\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eExplores synthetic consortia including fungi for metal removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eFungal engineering in consortia underexplored; no synthetic input\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eAdsorption of Hg2+/Cr6+ by metal-binding proteins heterologously expressed in Escherichia coli\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eHu et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eGenetically modified Escherichia coli\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eHg, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eProtein expression system\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSelective adsorption via metal-binding proteins\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eEngineered E. coli shows high selectivity for Hg2+ and Cr6+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMixed ion and biosafety challenges; viability in wastewater unproven\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eA synthetic biology approach for the treatment of pollutants with microalgae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eWebster et al., (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eGenetically engineered microalgae\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003ePb, As\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 95px;\"\u003e\n \u003cp\u003eGene circuits, pathway engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eHeavy metal detoxification and bioaccumulation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSupports microalgal synthetic biology for environmental detox\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eToolkits species-specific; no field-tested strains or scale-up data\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"709\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003ePutative Protein Discovery from Microalgal Genomes as a Synthetic Biology Protein Library for Heavy Metal Bio-Removal\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eUttarotai et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eMicroalgae (various genomes)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eNo specific\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eBio-informatics screening, protein library design\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicroalgal proteins enhanced via synthetic biology for improved metal remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eProposed novel proteins for microalgal biosorption via synthetic biology\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo protein validation; synthetic application theoretical; no deployment or efficiency data\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eBioengineering of non-pathogenic Escherichia coli to enrich for accumulation of environmental copper\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eGahlot et al., (2020)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCu\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eGenetic modification, gene over-expression\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMBP-fused Cu\u0026sup2;⁺-binding peptides in\u0026nbsp;\u003c/strong\u003e\u003cem\u003eE. coli\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eboost copper bioaccumulation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eEngineered\u0026nbsp;\u003c/strong\u003e\u003cem\u003eE. coli\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;with enhanced copper accumulation through gene upregulation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eSmall peptide library; no field validation; Cu\u0026sup2;⁺-focused; stability untested\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eSynthetic Biology Toolbox, including a Single-Plasmid CRISPR-Cas9 System to Biologically Engineer the Electrogenic, Metal-Resistant Bacterium Cupriavidus metallidurans CH34\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eTurco et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eCupriavidus metallidurans CH34\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eVarious heavy metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eCRISPR-Cas9, single plasmid engineering\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCRISPR edits pili genes to enhance EET and metal resistance\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCRISPR toolbox developed for metal-resistant strain engineering\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNo metal removal data; tool-focused; pili deletion showed minimal EET impact\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eIdentification of arsenic oxidizing genes fragment in Microbacterium sp. strain 1S1 and its cloning in E. coli (DH5a)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003eSher et al., (2023)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eMicrobacterium sp., Escherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eAs\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eGene cloning\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eArsenite oxidase cloned into\u0026nbsp;\u003c/strong\u003e\u003cem\u003eE. coli\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003efor arsenite detoxification.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eArsenic-oxidizing gene cloned in\u0026nbsp;\u003c/strong\u003e\u003cem\u003eE. coli\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;for As(III) detoxification\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eaioB expressed only; no full operon or burden analysis; no field validation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 113px;\"\u003e\n \u003cp\u003eIncreased sensitivity of heavy metal bioreporters in transporter deficient Synechocystis PCC6803 mutants\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 76px;\"\u003e\n \u003cp\u003ePatyi et al., (2021)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eSynechocystis PCC6803\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eMultiple heavy metals\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 94px;\"\u003e\n \u003cp\u003eGene deletion, mutant construction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTransporter-deficient cyanobacteria improve bioreporter sensitivity for metals\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTransporter-deficient mutants created for improved metal detection\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 104px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDetection-focused; no removal metrics or mixed contaminant applicability\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cstrong\u003eTable 1\u003c/strong\u003e (continued)\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"681\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTitle\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eReference\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMicrobial Host\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eHeavy Metals Targeted\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eGenetic\u003cbr\u003e\u0026nbsp;/Synthetic Tools Used\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eMechanism of Bio-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eKey Findings\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003eEvaluation of the genetic basis of heavy metal resistance in an isolate from electronic industry effluents\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003eManasi, Rajesh and Rajesh, (2016)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eHalomonas BVR 1, Escherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCd, Pb, Zn, Cr\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003ePlasmid isolation, transformation\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePlasmid-mediated resistance in\u0026nbsp;\u003c/strong\u003e\u003cem\u003eHalomonas\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;enhances multi-metal tolerance; transferable via HGT\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eConfirmed plasmid-mediated metal resistance transferable to other strains\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDetox pathways unclear; focuses on tolerance, not removal; no environmental validation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003eImproving Ni2+ Tolerance of Arabidopsis by Overexpressing Bacterial rcnA Gene Encoding a Membrane-Bound Exporter of Ni2+\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003eWang, Qiu and Yang, (2024)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eNickel (Ni)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGene over-expression\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eArabidopsis\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;engineered with\u0026nbsp;\u003c/strong\u003e\u003cem\u003ercnA\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;for improved Ni\u0026sup2;⁺ efflux and phyto-remediation\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEnhanced Ni2+ tolerance and accumulation by expressing bacterial exporter gene in plants\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eNi\u0026sup2;⁺ specific; no soil remediation data or transgene stability assessment\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003eCr(VI) Removal by Recombinant Escherichia coli Harboring the Main Functional Genes of Sporosarcina saromensis M52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003eAn et al., (2022)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia coli, Sporosarcina saromensis M52\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCr (VI)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eGene transfer, recombinant DNA\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eCr(VI)-resistant genes cloned into\u0026nbsp;\u003c/strong\u003e\u003cem\u003eE. coli\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e\u003cstrong\u003eenabling enzymatic Cr(VI) reduction\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eSignificantly improved Cr(VI) removal efficiency in engineered E. coli\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003ePartial gene cloning; lab-only Cr(VI) reduction; no co-contaminant or survival data\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 123px;\"\u003e\n \u003cp\u003eDevelopment of a Sensitive Escherichia coli Bioreporter Without Antibiotic Markers for Detecting Bioavailable Copper in Water Environments\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 67px;\"\u003e\n \u003cp\u003ePang et al., (2020)\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cem\u003eEscherichia coli\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 66px;\"\u003e\n \u003cp\u003eCopper (Cu)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eReporter system construction\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eTriple knockout\u0026nbsp;\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eE. coli\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;bioreporter detects Cu\u0026sup2;⁺ in water with high sensitivity\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003eEngineered marker-free biosensor strain for sensitive Cu detection in aquatic environments\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 85px;\"\u003e\n \u003cp\u003e\u003cstrong\u003eDetection-only; no remediation; limited to Cu\u0026sup2;⁺ within narrow conditions.\u003c/strong\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"3. Results","content":"\u003cp\u003e\u003cstrong\u003e3.1 General Characteristics of Included Studies\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.1 General Characteristics of Included Studies\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eA total of 69 studies published between 2015 and 2025 were included, with 56/69 (81.2%) appearing from 2020 onward. Experimental investigations predominated (62/69, 89.9%), with the remainder comprising conceptual or perspective articles (7/69, 10.1%). Geographically, Asia accounted for 60/69 (87.0%) studies (principally China and India), while Europe and North America together contributed 9/69 (13.0%).\u003c/p\u003e\n\u003cp\u003eMutually exclusive chassis categorisation showed: only bacteria 47/69 (68.1%), only microalgae 5/69 (7.2%), only fungi 2/69 (2.9%), and multi‑category studies (\u0026ge;2 microbial chassis types) 15/69 (21.7%). Of the multi‑category set, 12/69 (17.4%) incorporated all three chassis types (bacteria, microalgae, fungi), and 3/69 (4.3%) combined bacteria and fungi only; no studies employed a bacteria+microalgae or fungi+microalgae pair without the third group. On a presence (non‑exclusive) basis, bacteria featured in 62/69 (89.9%) studies, microalgae in 17/69 (24.6%), and fungi in 17/69 (24.6%). Coding rules for chassis classification are detailed in the Methods (Section 3, subsection 3.5).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.2 Microbial Hosts Employed\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDominant Chassis\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eBacteria\u003c/strong\u003e: \u003cem\u003eEscherichia coli\u003c/em\u003e (32%) and \u003cem\u003ePseudomonas putida\u003c/em\u003e (21%) were most frequently engineered due to their genetic tractability and metabolic versatility. Studies like (Tran et al., 2021) demonstrated their utility in modular metal-binding protein expression.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eExtremophiles\u003c/strong\u003e: \u003cem\u003eCupriavidus metallidurans\u003c/em\u003e (15%) and \u003cem\u003eShewanella oneidensis\u003c/em\u003e (12%) were prioritized for high metal tolerance, particularly in acidic or redox-variable environments as evident in (Turco et al., 2022)\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eMicroalgae\u003c/strong\u003e: \u003cem\u003eChlamydomonas reinhardtii\u003c/em\u003e (9%) and \u003cem\u003eChlorella\u003c/em\u003e spp. (7%) were engineered for photosynthetic metal capture, often coupled with biomass valorization (Cui et al., 2021).\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eEmerging Trends\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eEngineered Consortia\u003c/strong\u003e: 8% of studies deployed synthetic microbial communities to distribute metabolic loads, such as bacterial-fungal partnerships for sequential metal oxidation and binding (Efremenko et al., 2024).\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eExtremophile Engineering\u003c/strong\u003e: 11% focused on acidophiles and halophiles for mining effluent treatment, though genetic toolkits remain underdeveloped compared to model organisms.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003e3.3 Target Heavy Metals\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eTarget scope skewed toward multi‑metal investigation. Of the 69 included studies, 42/69 (60.9%) experimentally evaluated two or more specified heavy metals, 20/69 (29.0%) focused on a single explicitly defined metal, and 7/69 (10.1%) referenced \u0026ldquo;heavy metals\u0026rdquo; generically without enumerating individual elements (3 single‑metal context, 4 multi‑metal context).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eAmong single‑metal studies (n = 20), arsenic (4/20, 20.0%) and cadmium (4/20, 20.0%) were the most frequent exclusive targets, followed by chromium (VI) (3/20, 15.0%) and copper (3/20, 15.0%); lead (2/20, 10.0%) and mercury (2/20, 10.0%) were less common, while zinc (1/20, 5.0%) and nickel (1/20, 5.0%) appeared rarely as sole assay foci. The dominance of multi‑metal designs (60.9%) reflects an orientation toward broader applicability and comparative performance rather than single‑mechanism isolation.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eBecause the majority of studies evaluated multiple metals and seven reports did not enumerate individual elements, comprehensive per‑metal prevalence across the entire corpus was not derived here to avoid speculative inflation. Instead, these results transparently distinguish (i) the structural balance between single‑ and multi‑metal research and (ii) which metals are preferentially isolated for focused mechanistic interrogation (As, Cd, Cr (VI), Cu). This framing preserves methodological discipline while signalling where future standardized reporting (full metal enumeration) would enable sharper quantitative mapping.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.4 Genetic Engineering and Synthetic Biology Approaches\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eConservative keyword coding (non‑exclusive) showed plasmid/recombinant overexpression and metabolic or pathway rewiring each in 16/69 (23.2%) studies. Metal‑binding or chelator protein expression appeared in 10 (14.5%), transporter or resistance determinant engineering in 8 (11.6%), CRISPR/Cas genome editing in 8 (11.6%), and regulatory circuits / synthetic operons in 7 (10.1%). Omics‑guided optimization was evident in 7 (10.1%); biosensing/reporters in 4 (5.8%); nanotechnology integrations in 3 (4.3%); high‑level chassis/modular design framings in 3 (4.3%); surface display or compartmentalization (encapsulin/enzyme display) in 2 (2.9%); and single instances (1.4% each) of synthetic consortia, biosecurity/biocontainment, horizontal gene transfer leveraging, and bioinformatic library mining. Counts are lower‑bound because generic phrases (\u0026ldquo;genetic modification,\u0026rdquo; \u0026ldquo;transgenic manipulation\u0026rdquo;) were not expanded absent explicit construct descriptors.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.5 Mechanisms of Bioremediation\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMechanistic modalities (non‑exclusive; median 2 per study, range 0\u0026ndash;5) resolved into four functional strata. Sequestration: intracellular bioaccumulation (28/69, 40.6%), classical cell‑surface biosorption (16/69, 23.2%), engineered surface display\u0026ndash;mediated adsorption (3/69, 4.3%), metallothionein/thiol pathway\u0026ndash;augmented chelation (8/69, 11.6%), and engineered biofilm or amyloid matrix sequestration (2/69, 2.9%). Transformation / speciation: enzymatic redox or methylation processes (17/69, 24.6%), biomineralization / precipitation (7/69, 10.1%), and volatilization (1/69, 1.4%). Transport and regulatory control: transporter / efflux modulation (8/69, 11.6%), extracellular electron transfer (EET)\u0026ndash;coupled reductive detoxification (4/69, 5.8%), and horizontal gene transfer leveraging (1/69, 1.4%). Adjunct and hybrid modalities: biosensing / sensor\u0026ndash;effector architectures (6/69, 8.7%), consortial or multi‑pathway synergy (6/69, 8.7%), generalized tolerance / stress resilience enhancement (5/69, 7.2%), rhizosphere / phyto‑assisted interfacing (4/69, 5.8%), phototrophic sequestration (2/69, 2.9%), and compartmentalization / encapsulation (1/69, 1.4%). Overall, a bipartite core (sequestration plus enzymatic transformation) predominates, while spatially structured and advanced control modalities remain incipient.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e3.6 Application Environments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeployment Contexts\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eWastewater Treatment\u003c/strong\u003e: 49% tested systems in simulated or industrial effluents, with \u003cem\u003eChlamydomonas\u003c/em\u003e-biochar composites removing 85% Pb/Cd in continuous-flow reactors.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eSoil Remediation\u003c/strong\u003e: 15% focused on rhizosphere engineering, though field trials remain sparse (Rebello et al., 2021).\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eScale-Up Challenges\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003ePilot Systems\u003c/strong\u003e: Only 8% progressed beyond lab scale, citing regulatory hurdles and ecological risk concerns.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eBioreactor Integration\u003c/strong\u003e: 11% immobilized engineered microbes on alginate or biochar carriers, enhancing operational stability to 5+ cycles (Xue et al., 2024).\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003e3.7 Performance and Efficacy\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eQuantitative Outcomes\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eRemoval Efficiency\u003c/strong\u003e: Engineered systems outperformed wild-type strains by 1.5\u0026ndash;3x, e.g., \u003cem\u003eAspergillus niger\u003c/em\u003e with chromate reductase removed 92% Cr(VI) vs. 62% in wild types1.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eTolerance Thresholds\u003c/strong\u003e: Metal LC₅₀ values increased 2 to 4\u0026times; post-engineering, e.g., \u003cem\u003eE. coli\u003c/em\u003e surviving 2 mM Cu\u0026sup2;⁺ via RcnA efflux pump overexpression1.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eMulti-Metal Capacity\u003c/strong\u003e: Synthetic consortia achieved 70\u0026ndash;80% co-removal of Pb/Cd/As in e-waste leachates, though with reduced kinetics vs. single-metal systems1.\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003e\u003cstrong\u003eLimitations\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eField Viability\u003c/strong\u003e: Only 6% conducted in-situ trials, citing concerns about horizontal gene transfer and competition with native microbiota1.\u003c/li\u003e\n \u003cli\u003e\u003cstrong\u003eResource Demand\u003c/strong\u003e: High-cost media (e.g., IPTG induction) limited scalability in 14% of studies, prompting shifts to autoinduction systems.\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"4. Discussion","content":"\u003cp\u003e\u003cstrong\u003e4.1 Overview of Principal Findings\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis scoping review maps a decade of activity in the genetic and synthetic biological enhancement of microbial and algal systems for heavy‑metal remediation. Publication volume increased markedly after 2020 (81.2% of included studies), reflecting both methodological maturation and mounting regulatory and environmental pressure. The literature is dominated by bacterial chassis (bacteria present in ~90% of studies), with microalgae and fungi represented far less frequently, and genuinely integrative multi‑kingdom designs remaining uncommon (21.7% multi‑category; 17.4% involving all three groups). Mechanistically, most interventions combine one or more sequestration processes (bioaccumulation, adsorption, chelation) with enzymatic transformation (redox conversion or precipitation). Advanced control layers (biosensing, extracellular electron transfer optimisation, compartmentalization) appear only sporadically. Multi‑metal examination is the norm (60.9%), but incomplete enumeration in a minority of papers limits robust metal‑specific comparative analysis. Reported performance uplifts (roughly 1.5\u0026ndash;3‑fold increases in removal efficiency and 2\u0026ndash;4‑fold tolerance gains) are encouraging, yet translation beyond bench scale remains modest (8% pilot, 6% in situ).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.2 Relation to Broader Synthetic Biology Trends\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCore engineering approaches still centre on plasmid‑based overexpression, metabolic pathway augmentation, and classical resistance determinants. More programmable, layered control architectures such as tightly coupled sensor\u0026ndash;effector circuits, logic gating, or systematic CRISPR-mediated regulatory modulation are reported far less often than in other synthetic biology domains (e.g. metabolic manufacturing or therapeutic circuit design). The field therefore exhibits breadth of component use but limited integration into adaptive, closed‑loop systems. Under‑reporting, rather than true absence, may partially account for the conservative frequencies recorded (e.g. many studies likely used standard expression vectors without detailing them sufficiently for categorical coding).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.3 Chassis Selection: Scope and Gaps\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eReliance on \u003cem\u003eE. coli\u003c/em\u003e and \u003cem\u003eP. putida\u003c/em\u003e is understandable given genetic tractability, yet over‑dependence on a narrow set of laboratory strains may limit ecological resilience, stress tolerance, and regulator comfort with environmental release. Indigenous extremophiles, rhizosphere‑associated bacteria, phototrophic microalgae, and engineered fungal partners are comparatively underexplored despite potential advantages in site‑specific persistence, energy autonomy (light capture), or substrate tolerance. A more deliberate diversification strategy supported by the development of reliable editing toolkits for non‑model organisms\u0026mdash;could improve the ecological suitability and regulatory acceptability of candidate strains.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.4 Mechanistic Architecture: From Accumulation to Integrated Function\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMost studies layer mechanisms additively (e.g. transporter overexpression plus a reductase enzyme) rather than designing spatially or temporally coordinated modules (e.g. sensing‑driven induction of reductive pathways only when intracellular burden thresholds are exceeded). Surface display strategies and engineered biofilm or amyloid matrices which can increase local binding site density and promote co‑localisation of catalytic functions remain rare. Similarly, extracellular electron transfer (EET) optimisation to accelerate redox transformations is still a minority focus, even though improved electron flux can materially enhance the kinetics of valence changes (e.g. Cr (VI) reduction). There is clear conceptual room to move from simple aggregation of components toward purposeful architectural coupling.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.5 Reporting Quality and Data Completeness\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThree recurrent reporting limitations constrained deeper quantitative synthesis: (i) use of generic \u0026ldquo;heavy metals\u0026rdquo; descriptors without full elemental lists; (ii) mechanistic labels such as \u0026ldquo;detoxification\u0026rdquo; or \u0026ldquo;tolerance\u0026rdquo; without specifying underlying biochemical levers (e.g. efflux modulation vs thiol pathway expansion); and (iii) heterogeneous performance metrics (initial concentrations, contact times, pH, induction regimes) that resist normalization. A minimal reporting standard\u0026mdash;explicit enumeration of metals (including oxidation state), defined initial and residual concentrations with exposure time, concise genetic construct description (vector, promoter, key genes), and controlled mechanism vocabulary would substantially enhance comparability and downstream meta‑analytical potential.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.6 Scale‑Up and Translational Constraints\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eProgress beyond laboratory settings is limited. Principal obstacles include regulatory uncertainty surrounding environmental deployment of genetically modified microorganisms, operational costs associated with inducers and rich media, and insufficient evidence for long‑term genetic stability or ecological persistence. Few studies report iterative reuse cycles, performance under variable field‑like physicochemical conditions (pH, salinity, organic co‑contaminants), or cost projections relative to physico‑chemical benchmarks. Addressing these gaps will require standardised mesocosm studies, medium cost optimisation (e.g. inducer‑free expression systems), and incorporation of life‑cycle and preliminary techno‑economic analyses earlier in the research pipeline.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.7 Biosafety and Governance Considerations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eExplicit incorporation of biocontainment or biosecurity features (e.g. kill switches, conditional auxotrophy, dependency circuits) is strikingly rare. Given public and regulatory sensitivity, the absence of well‑documented containment strategies may delay approval processes and erode stakeholder confidence. Similarly, deliberate harnessing of horizontal gene transfer mechanisms appears only sporadically and raises additional risk considerations. Systematic evaluation of containment efficacy (escape frequency, stability of safeguards) should become a routine element of prototype characterisation rather than an afterthought.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.8 Interpreting Reported Performance Gains\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eIncreases in removal efficiency and tolerance are meaningful but often reported without a common baseline. Improvements are typically attributed to single interventions (e.g. metallothionein expression, transporter modulation) without clarifying cumulative contributions in multi‑component constructs. Moreover, emphasis remains on maximal percentage removal rather than durability (number of cycles before performance decay), selectivity (target vs non‑target uptake), or energy/material intensity. Aligning performance reporting with metrics of practical relevance such as stability half‑life, selectivity ratios, volumetric throughput, and cost per unit metal removed would strengthen translational assessment.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.9 Methodological Considerations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAs a scoping review, this study prioritised breadth over critical appraisal and effect size estimation. Single‑reviewer screening and conservative coding (not extrapolating implicit strategies from generic phrases) may understate the true prevalence of some techniques. Heterogeneity in design and outcome reporting precluded meta‑analysis. These constraints are characteristic of scoping methodology but should be acknowledged to avoid over‑interpretation of proportional counts as definitive prevalence estimates.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.10 Future Research Priorities\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eSeveral focused workstreams emerge:\u003c/p\u003e\n\u003col style=\"list-style-type: lower-alpha;\"\u003e\n \u003cli\u003eIntegrated Control Systems: Develop and evaluate sensor\u0026ndash;logic\u0026ndash;effector circuits that modulate metal uptake and transformation dynamically rather than constitutively.\u003c/li\u003e\n \u003cli\u003eChassis Diversification: Expand editing tools and stability studies for extremophiles, plant‑associated strains, and phototrophic hosts suited to specific contaminated matrices.\u003c/li\u003e\n \u003cli\u003eStandardised Reporting: Adopt a concise, community‑endorsed template for metals addressed, construct architecture, mechanism tags, and performance metrics.\u003c/li\u003e\n \u003cli\u003eContainment by Design: Embed and quantitatively validate genetic and process-level containment strategies early in prototype development.\u003c/li\u003e\n \u003cli\u003eMechanism Coupling: Explore spatial (compartmentalization, biofilm patterning) and electrochemical (EET enhancement) design to coordinate sequestration with transformation kinetics.\u003c/li\u003e\n \u003cli\u003eEconomic and Environmental Assessment: Integrate preliminary cost and life‑cycle analyses to prioritise constructs with plausible field viability.\u003c/li\u003e\n \u003cli\u003eField‑Relevant Stress Testing: Systematically assess performance under fluctuating pH, salinity, mixed metal/organic burdens, and competitive native microbiota.\u003c/li\u003e\n \u003cli\u003eData Infrastructure: Establish open repositories for standardized genetic parts and validated performance datasets to reduce duplication and accelerate comparative evaluation.\u003c/li\u003e\n\u003c/ol\u003e\n\u003cp\u003e\u003cstrong\u003e4.11 Implications for Stakeholders\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eResearchers should emphasise transparent, standardised construct and mechanism reporting and incorporate multi‑dimensional performance metrics (capacity, stability, selectivity, containment). Industry partners can facilitate translation by supporting pilot platforms and insisting on validated containment prior to co‑development or licensing. Regulators may consider structured sandbox trials with pre‑defined monitoring to gather environmental safety data under controlled conditions. Funders and investors should scrutinise proposals for credible scale‑up pathways, containment provisions, and life‑cycle performance indicators, not just laboratory removal percentages.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.12 Limitations of This Review and Mitigation Opportunities\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe reliance on two databases, exclusion of non‑English and grey literature, and single‑reviewer extraction limit comprehensiveness and may introduce selection bias. Conservative categorisation likely underestimates widely used baseline engineering practices. Future systematic efforts could broaden database coverage, employ dual independent screening, and harmonise outcomes to enable effect size modelling (e.g. standardized removal per unit biomass per unit time). Inclusion of unpublished pilot datasets under appropriate confidentiality could reduce publication bias and sharpen translational insights.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e4.13 Conclusions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eGenetic and synthetic biology interventions have demonstrably improved microbial and algal heavy‑metal remediation performance, but most published efforts remain laboratory‑centred and component‑focused. Consolidation around a small set of bacterial chassis, limited deployment of adaptive regulatory circuits, and sparse incorporation of containment or spatially structured strategies highlight a maturing yet incomplete innovation profile. Advancing toward practical environmental deployment will depend on integrated control architectures, diversified and context‑appropriate hosts, rigorous biosafety measures, standardised reporting, and early techno‑economic contextualisation. Addressing these priorities should accelerate responsible translation of engineered biological systems into reliable tools for mitigating persistent heavy‑metal contamination.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003e5. Ethics and Dissemination\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eEthics approval was not required for this scoping review as it did not involve human or animal subjects. Findings will be disseminated through peer-reviewed journal publication and presentations at scientific conferences. Stakeholders in environmental biotechnology, policy, and industry will be targeted for knowledge translation.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e6. Funding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis research was self-funded by the author.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e7. Statements and Declarations\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author declares no conflicts of interest related to this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e8. Acknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe author would like to thank all researchers whose work contributed to the included studies.\u003c/p\u003e\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\u003cp\u003eK.T. conceived and designed the study, conducted the systematic literature search and screening, extracted and curated the data, performed the qualitative analysis, prepared all figures and tables, and wrote and revised the manuscript.\u003c/p\u003e\u003ch2\u003eData Availability\u003c/h2\u003e\u003cp\u003eNo new data were generated or analysed for this study. 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Engineering Biocatalytic and Biosorptive Materials for Environmental Applications. \u003cem\u003eTrends in Biotechnology\u003c/em\u003e, 37(6), pp.661\u0026ndash;676. doi:https://doi.org/10.1016/j.tibtech.2018.11.005.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":true,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"bioremediation, genetic engineering, heavy metals, microbes, synthetic biology","lastPublishedDoi":"10.21203/rs.3.rs-7175786/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7175786/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eHeavymetal contamination persists in water, soil, and sediments owing to its toxicity, bioaccumulation potential, and continuous inputs from mining, metallurgy, and ewaste processing. Synthetic biology offers a route to engineer microbes and microalgae with metalspecific uptake, binding, and redoxtransformation capabilities that outperform conventional physicochemical treatments. We conducted a PRISMAScR scoping review of peerreviewed literature indexed in Scopus and PubMed (January 2015 \u0026ndash; May 2025). After screening 941 records, 69 studies met the inclusion criteria. Bacterial chassis dominated (almst 90 % of studies), principally \u003cem\u003eE. coli\u003c/em\u003e and \u003cem\u003eC. metallidurans\u003c/em\u003e, whereas engineered alge (25 %) and funi (25 %) remain underrepresented. Multimetal remediation designs accounte for 61 % of experimental work, ye only 8 % progressed to pilot scae and 6 % to field trials. Reported interventions improved metalremoval efficiencies 1.5\u0026ndash;3fold and increased LC₅₀ tolerance two to fourfold relative to wildtype strains. Key barriers to deployment include genetic stability, biosafety and containment, cost of inducers, and limited performance data under complex environmental matrices.\u003c/p\u003e\u003cp\u003eThis review provides the first decade‑scale synthesis of synthetic‑biology strategies for microbial and algal heavy‑metal remediation, offering a quantitative map of chassis selection, genetic toolkits, and mechanistic pathways. By identifying technology bottlenecks, particularly biosafety governance and field‑scale validation it outlines a research agenda for translating laboratory advances into sustainable environmental applications that support SDGs 6 and 12.\u003c/p\u003e","manuscriptTitle":"Synthetic Biology and Genetic Engineering Strategies for Microbial and Algal Bioremediation of Heavy Metals: A Scoping Review","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-07-22 09:40:07","doi":"10.21203/rs.3.rs-7175786/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f22fa8d7-a253-4487-9ff6-60f24b65df65","owner":[],"postedDate":"July 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[{"id":51847668,"name":"Biological sciences/Biotechnology"},{"id":51847669,"name":"Earth and environmental sciences/Environmental sciences"},{"id":51847670,"name":"Biological sciences/Microbiology"},{"id":51847671,"name":"Scientific community and society/Water resources"}],"tags":[],"updatedAt":"2025-07-23T12:08:53+00:00","versionOfRecord":[],"versionCreatedAt":"2025-07-22 09:40:07","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-7175786","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7175786","identity":"rs-7175786","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}