Evaluating the antibacterial activity and safety of bioactive compounds extracted from a brackish water Streptomyces cavourensis strain BA1

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Atallah, Eithar El-Mohsnawy, Hamdy E. Agwa, Ramadan El-domany This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8124036/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Antibiotic-resistant microorganisms pose a significant danger to civilization, particularly due to the lack of current effective antibiotics. This work included the isolation and identification of Streptomyces cavourensis strain BA1 (PX588109) by morphological and molecular characterization. The filtrate of the S. cavourensis strain BA1 showed significant antibacterial efficacy against two multidrug-resistant pathogens, Escherichia coli and Klebsiella pneumoniae . The ethyl acetate organic phase had the greatest inhibitory efficacy among the solvent extracts. GC-MS spectra revealed the presence of several potent antibacterial compounds: 9,12-Octadecadiens (Z,Z) TMS-derivate, Palmitins TMS-derivate, Linoleates trimethylsilyl ester, and Methyl-10,12-heptadecadienoleate. The cytotoxicity assessment prove that the oil toxins produced by ethyl acetate extracts are considered moderately safe for the kidney of African Green Monkey (VERO cell line), with CC50 values of 296.1 µg/ml. The findings demonstrate that S. cavourensis strain BA1 extracts had a positive safety profile, hence augmenting their potential for medicinal applications. The SEM images of E. coli cells treated with the filtrate of S. cavourensis strain BA1 exhibited irregularities, with some surface cells appearing dented, wrinkled, or fractured. The treated K. pneumoniae cells exhibited notable elongation in comparison to the control cells. Other cells exhibited pronounced creases and curvatures, with some cellular debris indicating potential leakage of cellular contents due to membrane rupture. These results underscore the significant bactericidal potential of fatty acids when combined with naturally occurring antimicrobial agents and facilitate future investigation of S. cavourensis strain BA1 as a unique ideal source of bioactive chemicals to address antibiotic resistance. bactericidal potential cytotoxicity fatty acids SEM Streptomyces cavourensis Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 1. Introduction Actinomycetes are one of the largest groups of Gram-positive bacteria with a high G ≡ C content [1, 2 ]. Due to their metabolic diversity and high antioxidant character, they are of vital technological importance, producing valuable secondary metabolites. These secondary metabolites are the main source of different antimicrobial agents, anti-inflammatory as well as anticancer [ 3 ]. Streptomyces , comprising over 700 species, represents the largest genus responsible for approximately two-thirds of natural antibiotics [ 4 ]. It serves as a notable competitor to multidrug-resistant (MDR) diseases [ 5 ]. Given the sharp increase in multidrug resistance bacteria, the discovery of new active ingredients is urgent. This situation is particularly problematic for highly resistant Gram-negative pathogens, such as Escherichia coli and Klebsiella pneumoniae for which few effective treatments are available [ 6 , 7 , 8 ]. Therefore, the pursuit of novel antibiotics or alternative strategies is essential. Actinomycetes derived from saline environments, such as fish farms, are less extensively studied compared to their soil-derived counterparts. Actinomycetes are predominantly located in soil; however, they also exist in aquatic environments, such as deep-sea sediments, representing a potential source of novel bioactive compounds [ 9 ]. This study demonstrates the significant antibacterial activity of the brackish-water bacterium S. cavourensis strain BA1 against two highly infectious pathogens, K. pneumoniae and E. coli . These findings facilitate further investigation of distinct actinomycete strains exhibiting antibacterial properties from comparable environments. 2. Materials and methods 2.1. Samples collection and isolation In May 2024, soil samples were collected in a range of 5 to 15 cm from distinct locations (Zubaida fish farm, situated southwest of Lake Burullus and largest Lake at the northern boundary of the Nile Delta, 31°23'57.2"N, 30°44'30.4"E), Egypt. Field measurements, pH-values and electrical conductivity (EC), were recorded according to the protocol of Kim and Park [ 10 ]. After 24 hours of air drying at 35°C, the dry soil samples were crushed and sieved through 2 mm mesh. Isolation was performed utilizing soil particles with diameters between 0.1 and 2 µm. For enrichment, nine milliliters of sterile distilled water was added to one gram of sieved soil. After serial dilutions to 10⁻⁴, 50 µL of each dilution level was added to starch nitrate agar, and the plates were incubated for seven days at 30°C [ 11 , 12 ]. The resulting colonies were then purified and examined further. 2.2. Morphological identification The morphological characteristics, including texture, aerial mycelium, substrate mycelium, growth rate, and pigmentation on starch-nitrate media, were analyzed. Shiriling and Gottlieb [ 13 ] observed that the colours of the aerial and reverse cultures were analyzed under standard lighting conditions. 2.3. Molecular identification Streptomyces cavourensis strain BA1 was cultured on starch-nitrate broth medium at 30°C, with shaking at 150 rpm for 7 days. Cultures were centrifuged at 3000 rpm for 20 min and the resulted pellet was used for the extraction of genomic DNA using EZ-10 Spin Column Bacterial Genomic DNA Miniprep Kits. Streptomyces cavourensis strain BA1 was partially sequenced by the 16S region. The 16S rDNA regions were amplified using the universal forward primer 27F 5’-AGAGTTTGATC (AC) TGGCTCAG–3’) and the reverse primer 1492R (5’-ACGG (CT) TACCTTGTTACGACTT-3’). The components and cycle conditions were controlled as described by Al-Dhabi et al [ 14 ]. The PCR reactions consisted of 4 µl of dNTPs (1.0 mM each, Roche, Penzberg, Germany), 2 µl of 10X buffer (Roche), 0.2 µl of each primer (0.5 µg), 0.2 µl of Taq polymerase (5 U/µl), 1 µl of 50 ng of template DNA, and sterile Milli-Q water in a final volume of 19.8 µl. The amplification conditions started by an initial denaturation at 94°C for 3 min, followed by 30 cycles of 94°C for 30 s, 50°C for 30 s, and 72°C for 1 min, and a final extension at 72°C for 7 min. The PCR-fragments were purified using the Qiagen PCR-purification kit (Qiagen, Hilden, Germany). The PCR products were examined by electrophoresis in a 1.5% agarose gel, stained with ethidium bromide, and visualized under UV transilluminator. The 16S rRNA genes of Streptomyces cavourensis strain BA1 was sequenced using the forward 27F primer and the Big Dye Terminator Cycle Sequencing kit v1.1. Sequencing reactions were run via the Applied Biosystems a 3500xL Genetic Analyzer, Foster city, California. The resulted nucleotide sequences were aligned throughout the GeneBank data, the BLAST-N program (Basic Local Alignment Search Tool-Nucleotides) from the NCBI website (National Center for Biotechnology Information). 2.4. Exploring the antibacterial potential of S. cavourensis strain BA1 Two serious pathogens, Escherichia coli and Klebsiella pneumoniae , were graciously acquired from the Microbial Biotechnology Unit at the Faculty of Science, Kafrelsheikh University. One ml of S. cavourensis strain BA1 spore suspension was inoculated into 50 ml of autoclaved starch-nitrate broth medium, cultured in a 250 ml Erlenmeyer flask. The culture was agitated at 30°C and 120 rpm for duration of 7 days. After the incubation period, the upper culture fluid was separated from S. cavourensis biomass by centrifugation at 3,000 g for 20 min. To test the inhibitory effect, fresh nutrient agar plates were evenly inoculated with 1 ml of 18-h culture broth of the respective test bacterial pathogens [ 15 ]. 5 mm diameter holes were punched in each prepared plate using a sterile cork punch. Each hole was filled with 100 µl of filtered upper culture fluid from S. cavourensis strain NRRL 2740. The plates were incubated for 24 h at 37°C. The width of the inhibition zone was then measured in mm [ 16 ]. 2.5. Partial purification of antibacterial compounds Cultured S. cavourensis strain BA1 was utilized as inoculum for one litre of culture broth. The culture was grown for 7 days at 30°C and 120 rpm in a shaking incubator (Thermo MaxQ 445). The biomass of S. cavourensis strain BA1 assembly using Whatman No. 1 filter paper, and the supernatant was centrifuged at 8,000 × g for 15 min at 4°C to reach a clear (filtered) solution [ 5 ]. The supernatant was then aseptically transferred to 250-ml conical flasks and treated with equal volumes (1:1, v/v) of n-butanol, ethyl acetate, and diethyl ether, respectively. The mixture was shaken vigorously for 20 min, followed by a 15-minute stand-off for phase separation. The aqueous and organic phases were separately concentrated at 40°C to evaporate the solvents and obtain a viscous crude extract. The residue was dried in a vacuum dryer to completely remove any residual solvents, weighed, and dissolved in 1 mg/ml methanol for the agar diffusion test. Each experiment used methanol as a control for dangerous bacteria. The best solvent was employed to extract antibacterial compounds [ 17 ]. A rotating evaporator (Heidolph, Germany) concentrated organic and aqueous phases to near dryness under reduced pressure. 2.6. Evaluation of cytotoxic effect of ethyl acetate extract The cytotoxicity of an ethyl acetate extract of S. cavourensis strain BA1 was studied in African green monkey kidney cells (VERO) according to the protocol of Mosmann [ 18 ] and Gomha et al [ 19 ]. 2.7. GC-MS analysis of ethyl acetate extract Bioactive compounds from the ethyl acetate extract of S. cavourensis strain BA1 were identified using gas chromatography-mass spectrometry (GC-MS). The analysis was performed using an Agilent 7890A GC system connected to an Agilent 5975C MS detector. A HP-5MS column (30 m × 250 µm × 0.25 µm) was used. Helium was used as the carrier gas at a constant flow rate of 1.5 mL/min. The oven temperature was increased according to the following program: 1 min at 90°C, then gradually increased at 8°C/min to 300°C, followed by a 30-minute stabilization phase. One microliter of sample was injected in splitless mode at an injector temperature of 290°C. The mass spectrometer operated at ionization energy of 70 electron volts and covered a mass range of 60 to 600 atomic mass units [ 20 ]. 2.8. Bactericidal potential of S. cavourensis strain BA1 filtrate A growth inhibition investigation was done to examine the bactericidal activity of the filtrate from S. cavourensis strain BA1 against two multidrug resistant pathogens, K. pneumoniae and E. coli . Approximately 500 µl of the filtrate was added to 9 ml of nutrient broth medium and inoculated with 500 µl of the bacterial suspensions (1 × 10⁵ CFU ml⁻¹), then incubated at 37°C for 24 h in a shaker incubator set to 150 rpm. All treatments were conducted in triplicate [ 21 ]. Control cultures were augmented with 500 µl of NB media in lieu of the filtrate from the S. cavourensis strain BA1. Bacterial growth was assessed by quantifying the turbidity of the cultures using a JASCO V-730 UV-Visible Spectrophotometer at 600 nm [ 22 ]. 2.9. Scanning electron microscopy (SEM) of bacterial cells Scanning electron microscopy (SEM) was used to observe and detect the alterations in the morphological properties of E. coli and K. pneumoniae in both control and treatment cultures. Cells for scanning electron microscopy (SEM) were prepared as follows: Cell pellets from treated and untreated bacteria were collected by centrifugation (12,000 g, 1 min). Each pellet was resuspended in 500 µL of phosphate-buffered saline (PBS, pH 7) containing 2% formaldehyde and 1% glutaraldehyde, then centrifuged again. The pellet was then washed twice with distilled water and resuspended in 1 mL distilled water. A 5-µL aliquot of this suspension was placed on a 5 mm × 5 mm silicon wafer and air-dried at room temperature [ 23 ]. The dried samples were examined using a field-emission scanning electron microscope (FE-SEM, JEOL JSM-IT200). 2.10. Statistical analysis All experiments were performed three times independently (n = 3). Data are presented as mean ± standard error of the mean. Statistical analysis was performed using SPSS (Statistical Package for the Social Sciences) software [ 24 ]. 3. Results 3.1. Identification of Streptomyces cavourensis strain BA1 3.1.1. Morphological characteristics The isolate exhibited a chalky appearance, pale yellow aerial mycelium, buff substrate mycelium, and little brown pigmentation (Fig. 1 ). The substrate mycelium of colonies was observable within 2 days of incubation. The emergence of colonies between the third and fifth day resembles a standard bacterial colony. Verification of an actinomycetal colony may be achieved by examining the colony's powdery texture. The colonies are firmly adhered to the agar surface, much to a plant anchored in soil. 3.1.2. Molecular identification (16S rRNA gene sequence analysis) The PCR-amplified 16S rRNA gene was 1500 bp (Fig. 2 ). The Foster City, California-based Applied Biosystems 3500xL Genetic Analyser was used to purify and sequence the amplified DNA. Sequence comparison to the National Center for Biotechnology Information database showed that the isolate is a member of the genus Streptomyces of the family Streptomycetaceae (phylum Actinobacteria). NCBI GenBank (Table 1 ) showed 100% similarity with Streptomyces cavourensis strain PES4. MUSCLE was used to match the sequence with 12 closely related Streptomyces species. Kumar et al [ 25 ] used MEGA-X software to merge their NCBI GenBank sequences for Neighbour-Joining phylogenetic analysis and Kimura 2-parameter evolutionary distance calculations. The phylogenetic tree (Fig. 3 ) confirmed the isolate's resemblance to S. cavourensis strain PES4. The partial 16S rRNA gene sequence of S. cavourensis strain BA1 has GenBank entry number PX588109. Table 1 Gene sequence alignments of 16S rRNA gene of the isolate Streptomyces cavourensis strain BA1 to the data available at NCBI (BLASTN) Description Max Score Total Score Query Cover E value Per. Ident Accession Streptomyces cavourensis strain PES4 16S ribosomal RNA gene, partial sequence 1242 1242 100% 0.0 100% OM909163.1 Streptomyces cavourensis strain A-2 16S ribosomal RNA gene, partial sequence 1236 1236 100% 0.0 99.85% KC178676.1 Streptomyces araujoniae strain HSA312 16S ribosomal RNA gene, partial sequence 1236 1236 100% 0.0 99.85% MN902069.1 Kitasatospora albolonga strain NBRC 13465 16S ribosomal RNA, partial sequence 1236 1236 100% 0.0 99.85% NR_041144.1 3.2. Antibacterial activity Table 2 and Fig. 4 highlight the potent antibacterial effects of S. cavourensis strain BA1 filtrate, with ethyl acetate organic extract emerging as a promising candidate for further exploration. The pathogen-specific responses suggest selective activity, warranting additional studies on compound isolation and potential synergistic formulations. S. cavourensis strain BA1 filtrate exhibited strong antibacterial effects, with inhibition zones up to 31 mm for K. pneumoniae and 23 mm for E. coli . Among the fractionated extracts, the ethyl acetate organic phase has demonstrated the highest inhibition against both pathogens, K. pneumoniae (24 mm) and E. coli (20 mm). While the ethyl acetate aqueous phase displayed relatively weak activity, suggesting that fewer active compounds are extracted into this phase. On the other hand, the n-butanol organic phase showed moderate inhibition of 11 mm for E. coli and 15 mm for K. pneumoniae , indicating selective antimicrobial properties. Table 2 Antibacterial Activity of Streptomyces cavourensis strain BA1 (mm). Zones of inhibition produced by the filtrate, aqueous layer, and organic fractions (n-butanol, ethyl acetate, diethyl ether) against Klebsiella pneumoniae and Escherichia coli Pathogen Inhibition zone (mm) S. cavourensis filtrate N-butanol organic phase N-butanol aqueous phase Ethyl acetate organic phase Ethyl acetate aqueous phase Diethyl ether organic phase Diethyl ether aqueous phase E. coli 23 ± 0.3 11 ± 0.5 9 ± 0.4 20 ± 0.3 9 ± 0.1 13 ± 0.6 11 ± 0.4 K. pneumonia e 31 ± 0.4 18 ± 0.2 9 ± 0.3 24 ± 0.5 8 ± 0.3 13 ± 0.2 11 ± 0.2 * Means with ± Standard errors 3.3. Cytotoxic evaluation Cytotoxicity examination of ethyl acetate extract of S. cavourensis strain BA1 on the VERO cell line is shown in Fig. 5 . Recorded data illustrated a moderate impact with a CC50 value of 296.1 µg/ml. The extract displays a safe profile for normal cells. Obtained data strongly recommend using it in medical applications for its potential safety advantages. 3.4. GC-MS Analysis Given its significant antibacterial activity against the studied pathogens, the ethyl acetate extract of S. cavourensis strain BA1 was analyzed using gas chromatography-mass spectrometry (GC-MS). Comparison of the spectra with the National Institute of Standards and Technology (NIST) database confirmed the presence of five bioactive compounds with antibacterial activity (Fig. 6 ). As shown in Table 3 , the most abundant compounds were the 9,12-octadecadienoic acid derivative (Z,Z)-TMS (21.5% of the peak area) and the palmitic acid derivative-TMS (19.6%). In addition, linoelaidic acid, trimethylsilyl ester (6.6%), bis (2-ethylhexyl) phthalate (3.8%), and methyl 10,12-heptadecadiynoate (3.0%) were detected. The GC-MS profile (Fig. 6 ) visually supports the quantitative data from Table 3 , confirming the presence and relative abundance of bioactive compounds. Peak area percentages from Table 3 correspond well with peak intensities in Fig. 6 . Table 3 Identified bioactive compounds detected by GC-mass spectroscopy of S. cavourensis strain BA1 ethyl acetate extract N Name of the compound Molecular formula Molecular weight Retention time (Min) Peak area (%) Activity Reference 1 Methyl 10,12-heptadecadiynoate C 18 H 28 O 2 276 4.22 3.0 Antibacterial ]33[ 2 Palmitic Acid, TMS derivative C 19 H 40 O 2 Si 328 28.90 19.6 Antimicrobial ]31[ 3 9,12-Octadecadienoic acid (Z,Z)-,TMS derivative C 21 H 40 O 2 Si 352 31.70 21.5 Antimicrobial ]30[ 4 Linoelaidic acid, trimethylsilyl ester C 21 H 40 O 2 Si 352 31.97 6.6 Antibacterial ]32[ 5 Bis (2-ethylhexyl) phthalate C 24 H 38 O 4 390 36.62 3.8 Antibacterial ]34[ 3.5. Bactericidal potentiality of S. cavourensis strain BA1 Scanning electron microscopy (SEM) images offer definitive visual proof of the antibacterial activities of the S. cavourensis filtrate (Fig. 7 ). The picture of untreated E. coli (control group) has the characteristic rod shape, exhibiting a smooth surface and intact cellular structure, signifying healthy, unmodified cells (Fig. 7 a). Conversely, Fig. 7 b illustrates considerable structural damage, characterized by irregularities, with several surface cells exhibiting dents, wrinkles, or fractures. Indicators of membrane rupture, shrinkage, or surface roughness are apparent in E. coli subjected to the filtrate. The untreated Klebsiella pneumoniae (control group) displays a capsule-like morphology with smooth contours, while the treated strain demonstrates pronounced morphological alterations, including cell wall breakdown or collapse and considerable elongation relative to the control cells. Additionally, other cells exhibited pronounced wrinkles and curvatures, with some cellular debris indicating potential leakage of cell contents due to membrane rupture (Fig. 7 c, Fig. 7 d). 4. Discussion This work isolated the S. cavourensis strain BA1 from the Zubaida fish farm, situated southwest of Lake Burullus in Egypt, a distinctive habitat with potential for novel microbial discoveries. Morphological and molecular analyses verified its classification within the phylum Actinobacteria, family Streptomycetaceae, and genus Streptomyces , demonstrating a 100% similarity to S. cavourensis strain PES4 and a 99.85% to both Streptomyces araujoniae strain HSA312 and Kitasatospora albolonga strain NBRC 13465 in NCBI GenBank. According to Silva et al [ 26 ], Streptomyces araujoniae has white aerial mycelium with no production of diffusible pigments on starch nitrate agar. Bergey's Manual of Systemic Bacteriology [ 27 ] states that Kitasatospora albolonga exhibits beige colonies and is characterized by an absence of melanin synthesis. Our strain, Streptomyces cavourensis strain BA1 (PX588109), exhibited pale yellow aerial mycelium and produced melanin pigments on SNA media. The filtrate of S. cavourensis strain BA1 exhibited significant bactericidal effect against investigated pathogens, K. pneumoniae and E. coli . The ethyl acetate organic phase had the greatest inhibitory efficacy among the solvent extracts. K. pneumoniae and E. coli exhibited significant sensitivity to the filtrate, although shown reduced sensitivity to the solvent fractions. The elevated inhibitory zones noted in the filtrates corroborate the concept that many bioactive components function synergistically [ 28 ]. Conversely, the ethyl acetate aqueous phase exhibited the least inhibition, indicating reduced quantities or diminished solubility of the bioactive compounds. Cytotoxicity is a fundamental aspect of antibacterial research. Numerous effective antibacterial drugs demonstrate cytotoxic effects on eukaryotic cells [ 29 ]. This study's cytotoxicity assessment revealed a moderate impact on the VERO cell line, with CC50 values of 296.1 µg/ml for the ethyl acetate extract. The results demonstrate that S. cavourensis strain BA1 extracts had a positive safety profile, hence augmenting their potential for medical applications. Gas chromatography-mass spectrometry analysis of the ethyl acetate extract confirmed the presence of four effective antibacterial fatty acids: 9,12-octadecadienoic acid (Z,Z)-, a TMS derivative (21.5%), palmitic acid, a TMS derivative (19.6%), linoleic acid, a trimethylsilyl ester (6.6%) and methyl 10,12-heptadecadinoate (3.0%). Furthermore, bis(2-ethylhexyl) phthalate was identified at a concentration of 3.8%. Numerous prior studies demonstrated that these chemicals exhibit significant antibacterial activity against various Gram-positive and Gram-negative microorganisms. Gas chromatography-mass spectrometry (GC-MS) analysis of the ethyl acetate extract of Streptomyces sp. MMM2 identified four active fatty acids: 9,12-octadecadienoic acid (PUA) exhibited antibacterial activity against various pathogenic bacteria, including Staphylococcus aureus ( S. aureus ) and Escherichia coli [ 30 ]. Palmitic acid, a saturated fatty acid, exhibited remarkable antibacterial activity against several pathogens, such as K. pneumoniae and P. aeruginosa [ 31 ]. Linoleic acid, an omega-6 trans-unsaturated fatty acid, isolated from watermelon seed oil, exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria [ 32 ]. Methyl 10,12-heptadecadinoate, a saturated fatty acid from Piper longum , exhibits bactericidal activity against multidrug-resistant Salmonella strains [ 33 ]. Furthermore, bis(2-ethylhexyl) phthalate from Lactobacillus plantarum has shown antibacterial activity against Escherichia coli and Staphylococcus aureus [ 34 ]. The SEM images of the morphology of E. coli cells treated with the filtrate of S. cavourensis strain BA1 exhibited irregularities, with certain surface cells appearing dented, wrinkled, or fractured. Moreover, the delineation of the cell wall boundary was ambiguous in several cells. Conversely, the treated K. pneumoniae cells exhibited notable abnormalities in comparison to the control cells. Other cells exhibited pronounced creases and curvatures, with some cellular debris indicating potential leakage, perhaps due to the degradation of cell membranes and the subsequent efflux of cellular contents. Chouhan et al [ 35 ] assert that the hydrophobic characteristics of oils facilitate their penetration into the lipid bilayers of bacterial cell membranes, hence disturbing their integrity and enhancing permeability, resulting in the leakage of ions and cellular contents. Saturated fatty acids, including palmitic acid and methyl 10,12-heptadecadiynoate, are thought to compromise bacterial cell membranes, perhaps leading to cell lysis or disruption of essential biological processes [ 36 ]. Yoon et al [ 37 ] discovered that unsaturated fatty acids, including 9,12-octadecadienoic acid, can infiltrate bacterial cell membranes, modifying their structure and function, which leads to cell death and the release of intracellular contents. Furthermore, the enzyme enoyl-acyl carrier protein reductase (FabI), crucial for bacterial fatty acid synthesis, can be blocked by specific unsaturated fatty acids, including linoleic acid. This disruption of fatty acid synthesis may inhibit bacterial growth and survival [ 38 ]. Moreover, the antibacterial efficacy of the oil fluctuates based on the specific bacterial strain and the type of oil analyzed. Consequently, growth suppression may result from multiple components functioning synergistically [ 39 ]. This corroborates our findings that the filtrate of S. cavourensis strain BA1 exhibited superior antibacterial activity against the investigated pathogens compared to any other solvent fraction. Conclusion This work reports the initial isolation of the brackish actinomycete strain S. cavourensis strain BA1 from the brackish sediments of the Zubaida fish farm, situated southwest of Lake Burullus in Egypt. The isolate was characterized by morphological and molecular methods. Its filtrate consistently yielded larger inhibitory zones than fractionated solvents, indicating that several bioactive chemicals function synergistically within the whole filtrate. The ethyl acetate organic phase had significant action. Ethyl acetate extract has demonstrated moderate cytotoxic effects on the VERO cell line, suggesting possible safety attributes. The GC-MS spectra of the ethyl acetate extract verified the existence of five bioactive components. Four of these were potent antibacterial fatty acids. Furthermore, bis(2-ethylhexyl) phthalate was identified. The SEM images of the morphology of E. coli cells treated with S. cavourensis strain BA1 filtrate exhibited irregularities, with some surface cells appearing dented, wrinkled, or fractured. The treated K. pneumoniae cells exhibited considerable elongation in comparison to the control cells. Other cells exhibited pronounced creases and curvatures, accompanied by cell debris indicative of membrane rupture and the subsequent efflux of cellular contents. The results validate the substantial bactericidal effectiveness of fatty acids from S. cavourensis strain BA1 in conjunction with naturally occurring antimicrobial agents and encourage future exploration of the S. cavourensis strain BA1 as a potential source of bioactive compounds to address antibiotic resistance. Declarations Acknowledgments Not applicable. Author contributions All authors contributed to the study conception. BA, RE and EE designed experiments. Material preparation BA, RE and EE. Statistical analysis and figures preparation were performed by BA. EE, RE and HA supervised the work. All authors commented on the 1st version of the manuscript. All authors read and approved the final manuscript. Funding No fund was received during this work. Data availability Data generated during the current study are available in the supplementary file. Sequence data that support the findings of this study have been deposited in the NCBI’s Sequence Read Archive under accession number PX588109. Ethics approval and consent to participate Not applicable. Consent for publication Not applicable. Competing interests The authors declare that they have no competing interests. Author details Basma M. Atallah, Hamdy Agwa, and Eithar El-Mohsnawy Microbial Biotechnology Unit, Botany and Microbiology Department, Faculty of Science, Kafrelsheikh University, Kafrelsheikh, 33516, Egypt Basma M. Atallah[0009-0008-9435-5510] Hamdy E. Agwa [0009-0004-2739-9012] Eithar El-Mohsnawy[0000-0002-0060-3421] Ramadan El-domany Microbiology and Immunology Department, Faculty of Pharmacy, Kafrelsheikh University, Kafrelsheikh, 33516, Egypt Ramadan El-domany [https://orcid.org/0000-0001-6817-0151] References Barka A, Vatsa P, Sanchez L, Gaveau-Vaillant N, Jacquard C, Meier-Kolthoff P, Klenk P, Clément C, Ouhdouc Y, Van Wezel P. Taxonomy, Physiology, and natural products of actinobacteria. Microbiology and Molecular Biology Reviews 2016; 9:80. https://doi.org/10.1128/mmbr.00044-16. De Simeis D, Serra S. Actinomycetes: a never-ending source of bioactive compounds—an overview on antibiotics production. Antibiotics 2021; 10:483. https://doi.org/10.3390/antibiotics10050483. Khan S, Gul A, Jehan S, Khan Z, Saeed J, Shirazi R, Raziq A, Waseem M, Ullah H. Biodiversity of actinomycetes and their secondary metabolites: A Comprehensive Review. Journal of advanced Biomedical and Pharmaceutical Sciences 2023; 6:36-48. https://doi.org/10.21608/jabps.2022.161607.1165. Rammali S, Hilali L, Dari K, Bencharki B, Rahim A, Timinouni M, Gaboune F, El Aalaoui M, Khattabi A. Antimicrobial and antioxidant activities of Streptomyces species from soils of three different cold sites in the Fez-Meknes region Morocco. Scientific Reports 2022;12:17233. https://doi.org/10.1038/s41598-022-21644-z. Atallah B, El-Mohsnawy E, El-shouny W, Haroun S. Identification and characterization of different potentially antibacterial compounds from a marine Streptomyces sp. Sp1. Journal of Animal and Plant Sciences 2023;33:166-173. https://doi.org/10.36899/japs.2023.1.0605. Hassan M, El Sersy A, Abdelwahab S, Ali R. Statistical optimization and valuable applications of bioactive compounds produced by marine Pseudoalteromonas piscicida . J. Appl. Pharm. Sci 2017;84-93. https://doi.org/10.7324/japs.2017.71012. Nessim R, Tadros H, Moawad M, El-Sayed A, Deghady E, Abou Taleb A. Major constituents’ distribution as an indicator of water exchange between lake Burullus and the Mediterranean Sea. Blue Econ; 2024; 2:3. https://doi.org/10.57241/2805-2994.1017. Zhou L, Feng S, Sun G, Tang B, Zhu X, Song K, Zhang X, Lu H, Liu H, Sun Z. Extensively drug-resistant Gram-negative bacterial bloodstream infection in hematological disease Infect. Drug Resist 2019;12:481. 10.2147/IDR.S191462 Ngamcharungchit C, Chaimusik N, Panbangred W, Euanorasetr J. Intra bioactive metabolites from terrestrial and marine actinomycetes. Molecules 2023; 28:5915. https://doi.org/10.3390/molecules28155915. Kim N, Park H. Monitoring of soil EC for the prediction of soil nutrient regime under different soil water and organic matter contents. Appl. Biol. Chem 2024;67:1. https://doi.org/10.1186/s13765-023-00849-4. Ahmad S, El –Gendy O, Ahmed R, Hassan M, El –Kabbany M, Merdash G. Exploring the antimicrobial and antitumor potentials of Streptomyces sp. AGM12-1 isolated from Egyptian soil. Front. Microbiol 2017; 8:438. https://doi.org/ 10.3389/fmicb.2017.00438. Prashanthi R, et al. Isolation, characterization, and molecular identification of soil bacteria showing antibacterial activity against human pathogenic bacteria J. Genet. Eng. Biotechnol 2021;18:19-120. https://doi.org/10.1186/s43141-021-00219-x. Shirling B, Gottlieb D. Methods for Characterization of Streptomyces Species. Int.J. Syst Bacterial 1966; 6(3):13-340. https://doi.org/10.1099/00207713-16-3-313. Al-Dhabi N, Esmail G, Duraipandiyan V, Valan Arasu M, Salem-Bekhit M. Isolation, identification and screening of antimicrobial thermophilic Streptomyces sp. Al-Dhabi-1 isolated from Tharban hot spring, Saudi Arabia. Extremophiles 2016; 20:79-90. https://doi.org/10.1007/s00792-015-0799-1. Atallah B, Haroun S, El-Mohsnawy E. Antibacterial activity of two actinomycetes species isolated from black sand in North Egypt. South African Journal of Science 2023;119:11-12. https://doi.org/10.17159/sajs.2023/14509 Sathiyanarayanan G, Gandhmathi R, Sabarathnan B, SeghalKiran G, Selvin J. Optimization and production of pyrrolidon antimicrobial agent from marine sponge-associated Streptomyces sp. MAPSIS. Bioprocess. Biosyst. Eng 2014; 37:561-573. https://doi.org/10.1007/s00449-013-1023-2. Holmalahti J, Von Wright A, Raatikainen O. Variations in the spectra of biological activities of actinomycetes isolated from different soils. Lett. Appl. Microbiol 1994;18:144-146. https://doi.org/10.1111/j.1472-765x.1994.tb00829.x. Mosmann T. Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays. Immunol. Methods 1983; 65:55-63. https://doi.org/10.1016/0022-1759(83)90303-4. Gomha M, Riyadh M, Mahmmoud A, Elaasser M. Synthesis and anticancer activities of Thiazoles, 1,3-Thiazines, and Thiazolidine Using Chitosan-Grafted-Poly(vinylpyridine) as Basic Catalyst. Heterocycles 2015;91:1227-1243. https://doi.org/10.3987/com-15-13210. Hassan S, Shobier A. GC/MS identification and applications of bioactive seaweed extracts from Mediterranean coast of Egypt. EJABF 2018;5:1-21. https://doi.org/10.21608/ejabf.2018.17952. Hamouda R, Hussein H, Abo-elmagd A, et al . Synthesis and biological characterization of silver nanoparticles derived from the cyanobacterium Oscillatoria limnetica. Sci. Rep 2019;13071. https://doi.org/10.1038/s41598-019-49444-y. El-Mohsnawy E, El-Shaer A, El-Gharabawy F, et al. Assignment of the antibacterial potential of Ag2O/ZnO nanocomposite against MDR bacteria Proteus mirabilis and Salmonella typhi isolated from bone marrow transplant patients. Braz. J. Microbiol 2023; 54:2807-2815. https://doi.org/10.1007/s42770-023-01138-4. Naskar A, Lee S, Kim K. Easy one-pot low-temperature synthesized Ag-ZnO nanoparticles and their activity against clinical isolates of methicillin-resistant Staphylococcus aureus . Front. Bioeng. Biotechnol 2020;8:216. https://doi.org/10.3389/fbioe.2020.00216. Lorowitz W, Saxton E, Sondossi M, Nakaoka K. Integrating statistics with a microbiology laboratory activity. Microbiol. Educ 2005; 6:14-19. https://doi.org/10.1128/me.6.1.14-19.2005. Kumar S, Stecher G, Tamura K. MEGA7: Molecular Evolutionary Genetics Analysis Version 7.0 for Bigger Datasets. Mol. Biol. Evol 2016; 33:1870-4. https://doi.org/10.1093/molbev/msw054. Silva L, et al. Streptomyces araujoniae sp. nov.: An actinomycete isolated from a potato tubercle. Antonie-van-Leeuwenhoek 2013; 103:6. https://doi.org/10.1007/s10482-013-9901-9. Bergey's Manual of Systematic Bacteriology The Actinobacteria. New York: Springer 2012. https://doi.org/10.1007/978-0-387-68233-4_3. Hassan G, Abdel-Monem O, Sleem A,et al. Antimicrobial, antibiofilm, cytotoxicity, and anti-DNA topoisomerase activity of Streptomyces sp. 22SH with ADME and in silico study. BMC Microbiol 2025;25:219. https://doi.org/10.1186/s12866-025-03912-w. Zipperer A, Kretschmer D. Cytotoxicity assays as predictors of the safety and efficacy of antimicrobial agents Methods. Mol. Biol 2017; 1520:107-118. https://doi.org/10.1007/978-1-4939-6634-96. Malash M, et al. Antimicrobial Activities of a Novel Marine Streptomyces sp. MMM2 Isolated from El- Arish coast, Egypt. Egyptian Journal of Aquatic Biology and Fisheries 2022; 26:1317-1339. https://doi.org/10.21608/ejabf.2022.268783. Joujou M, Darra E, Rajha N, et al. Evaluation of synergistic/antagonistic antibacterial activities of fatty oils from apricot, date, grape, and black seeds. Sci. Rep 2024; 14:6532. https://doi.org/10.1038/s41598-024-54850-y. Soliman M, Abdel-Wahhab A. Synthesis of antibacterial bioactive compounds using linoleic acid extracted from Melon seeds oil and evaluation of its waste meal ash for fried oil regeneration .Waste Biomass Valor 2024; 15:487-499. https://doi.org/10.1007/s12649-023-02161-0. Rawat P, et al. Antibacterial, antioxidant, and phytochemical analysis of Piper longum fruit extracts against multi-drug resistant non-typhoidal Salmonella strains in vitro. Journal of Applied and Natural Science 2022; 14:1225-1239. https://doi.org/10.31018/jans.v14i4.3774. Javed R, Salman M, Tariq A, Tawab A, Zahoor K, Naheed S, Shahid M, Ijaz A, Ali H. The antibacterial and larvicidal potential of bis-(2-Ethylhexyl) phthalate from Lactiplantibacillus plantarum . Molecules 2022;27:7220. https://doi.org/10.3390/molecules27217220. Chouhan S, Sharma K, Guleria S. Antimicrobial activity of some essential oils-present status and future perspectives. Medicines (Basel) 2017;4:58. https://doi.org/10.3390/medicines4030058. Arellano H, Nardello-Rataj V, Szunerits S, Boukherroub R, Fameau L. Saturated long chain fatty acids as possible natural alternative antibacterial agents: Opportunities and challenges Adv. Colloid. Interface. Sci 2023; 318:102952. https://doi.org/10.1016/j.cis.2023.102952. Yoon K, Jackman A, Valle-González R, Cho J. Antibacterial free fatty acids and monoglycerides: biological activities, experimental testing, and therapeutic applications. Int. J. Mol. Sci 2018; 19:1114. https://doi.org/10.3390/ijms19041114. Batistel F, Gonzalez O, Sears A, Khan U, de Souza J. Palmitic acid alone or combined with stearic and oleic enhances ruminal fiber degradation and alters microbiome composition. Front. Microbiol 2025;16:1624738. https://doi.org/10.3389/fmicb.2025.1624738. Atta S, Waseem D, Fatima H, Naz I, Rasheed F, Kanwal N. Antibacterial potential and synergistic interaction between natural polyphenolic extracts and synthetic antibiotic on clinical isolates Saudi. J. Biol. Sci 2023;3:103576. https://doi.org/10.1016/j.sjbs.2023.103576. Additional Declarations No competing interests reported. Supplementary Files supplementarydataAtallahetal.28.11.2025BMC.pdf supplementarydataAtallahetal.04.12..2025BMC.pdf Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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01:07:52","extension":"html","order_by":36,"title":"","display":"","copyAsset":false,"role":"acdc-reference","size":145451,"visible":true,"origin":"","legend":"","description":"","filename":"earlyproof.html","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/6cb4508d4f398bb50f725feb.html"},{"id":98435695,"identity":"2855ab29-463f-42de-bdd0-db6f103db41b","added_by":"auto","created_at":"2025-12-17 16:54:12","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":528899,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eColony reverses appearance of\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003e Streptomyces cavourensis\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e strain BA1.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/80d386202e23605e9381afe9.png"},{"id":98269422,"identity":"18cd3ff0-9276-49c8-a76f-6c8dc24a25fb","added_by":"auto","created_at":"2025-12-16 01:07:51","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":169960,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003ePCR amplified 16S rRNA gene. Lane 1: Molecular weight of 100 bp ladder, Lane 2: amplified DNA fragment of ~1500 bp from \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eStreptomyces cavourensis \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003estrain BA1.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/234de9aaafe94826d73b5536.png"},{"id":98269436,"identity":"641d0dbf-9460-41b1-b4bd-5e483fe48ed0","added_by":"auto","created_at":"2025-12-16 01:07:51","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":297796,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eA phylogenetic tree of\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003e Streptomyces cavourensis \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003estrain BA1 illustrates how close\u003c/strong\u003e\u003cem\u003e \u003c/em\u003e\u003cem\u003e\u003cstrong\u003eS. cavourensis \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003estrain BA1 against other \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eStreptomyces \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003eneighbors. It has been reconstructed using MEGA-X software (Kumar et al. 2016).\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/a360705e531359c6914762b6.png"},{"id":98269424,"identity":"dc24f89b-61f5-4395-9670-81ae8c5be539","added_by":"auto","created_at":"2025-12-16 01:07:51","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":353479,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eAntibacterial evaluation of aqueous and organic layers of n-butanol, ethyl acetate, and diethyl ether against tested pathogens. \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eK. pneumoniae \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e(a) and \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eE. coli \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e(b).\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003e \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e1: n-butanol organic phase, 2: n-butanol aqueous phase, 3: ethyl acetate organic phase, 4: ethyl acetate aqueous phase, 5: diethyl ether organic phase, and 6: diethyl ether aqueous phase.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/c7b4e52f4946909eee1d0a51.png"},{"id":98433821,"identity":"c0961418-679c-44c4-93ad-d74fe67fedf7","added_by":"auto","created_at":"2025-12-17 16:51:09","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":109872,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eThe cytotoxicity impact of the ethyl acetate extract of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eS. cavourensis \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003estrain BA1 on VERO cell line after a 48-hour incubation period.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/c66916de176b27b76089138b.png"},{"id":98433923,"identity":"a91dc5da-2996-4a15-bb43-c90be0d6cf5e","added_by":"auto","created_at":"2025-12-17 16:51:16","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":242873,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eGC-MS chromatography profile of the ethyl acetate extract of\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003e S. cavourensis \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003estrain BA1.\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/501190a19aea8d83320a4ad3.png"},{"id":98269437,"identity":"939eb107-4fd4-4423-867b-27f786dadd71","added_by":"auto","created_at":"2025-12-16 01:07:51","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":881638,"visible":true,"origin":"","legend":"\u003cp\u003e\u003cstrong\u003eScanning electron microscopy images of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eE. coli \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003eand\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eK. pneumoniae\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e. (a) \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eE. coli\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e untreated (control), (b) \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eE. coli\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003etreated with \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eS. cavourensis \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003estrain BA1 filtrate, (c) \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eK. pneumoniae\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003euntreated (control), and (d)\u003c/strong\u003e\u003cem\u003e\u003cstrong\u003e K. pneumoniae\u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003e treated with the filtrate of \u003c/strong\u003e\u003cem\u003e\u003cstrong\u003eS. cavourensis \u003c/strong\u003e\u003c/em\u003e\u003cstrong\u003estrain BA1 (magnification 10 000X).\u003c/strong\u003e\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/a0c4b8947758d3a3207769ab.png"},{"id":103389822,"identity":"e5e1f49b-e7ed-4552-84a9-afcb555cf93e","added_by":"auto","created_at":"2026-02-25 07:27:39","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":4754405,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/f7bfbf10-c278-439f-9194-bdc2944d1d5d.pdf"},{"id":98269427,"identity":"4af70455-3b73-4491-9b5d-c2bb9fd81d2a","added_by":"auto","created_at":"2025-12-16 01:07:51","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":1180947,"visible":true,"origin":"","legend":"","description":"","filename":"supplementarydataAtallahetal.28.11.2025BMC.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/bc4be69834dbf11010365539.pdf"},{"id":98434592,"identity":"a076bf5d-9b12-4bca-9887-3789fb8ceffb","added_by":"auto","created_at":"2025-12-17 16:52:22","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1236577,"visible":true,"origin":"","legend":"","description":"","filename":"supplementarydataAtallahetal.04.12..2025BMC.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8124036/v1/55d7513d0e9aab7355bd19d8.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Evaluating the antibacterial activity and safety of bioactive compounds extracted from a brackish water Streptomyces cavourensis strain BA1","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eActinomycetes are one of the largest groups of Gram-positive bacteria with a high G\u0026thinsp;\u0026equiv;\u0026thinsp;C content [1, 2 ]. Due to their metabolic diversity and high antioxidant character, they are of vital technological importance, producing valuable secondary metabolites. These secondary metabolites are the main source of different antimicrobial agents, anti-inflammatory as well as anticancer [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. \u003cem\u003eStreptomyces\u003c/em\u003e, comprising over 700 species, represents the largest genus responsible for approximately two-thirds of natural antibiotics [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. It serves as a notable competitor to multidrug-resistant (MDR) diseases [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. Given the sharp increase in multidrug resistance bacteria, the discovery of new active ingredients is urgent. This situation is particularly problematic for highly resistant Gram-negative pathogens, such as \u003cem\u003eEscherichia coli\u003c/em\u003e and \u003cem\u003eKlebsiella pneumoniae\u003c/em\u003e for which few effective treatments are available [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. Therefore, the pursuit of novel antibiotics or alternative strategies is essential. Actinomycetes derived from saline environments, such as fish farms, are less extensively studied compared to their soil-derived counterparts. Actinomycetes are predominantly located in soil; however, they also exist in aquatic environments, such as deep-sea sediments, representing a potential source of novel bioactive compounds [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. This study demonstrates the significant antibacterial activity of the brackish-water bacterium \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 against two highly infectious pathogens, \u003cem\u003eK. pneumoniae\u003c/em\u003e and \u003cem\u003eE. coli\u003c/em\u003e. These findings facilitate further investigation of distinct actinomycete strains exhibiting antibacterial properties from comparable environments.\u003c/p\u003e"},{"header":"2. Materials and methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003e2.1. Samples collection and isolation\u003c/h2\u003e \u003cp\u003eIn May 2024, soil samples were collected in a range of 5 to 15 cm from distinct locations (Zubaida fish farm, situated southwest of Lake Burullus and largest Lake at the northern boundary of the Nile Delta, 31\u0026deg;23'57.2\"N, 30\u0026deg;44'30.4\"E), Egypt. Field measurements, pH-values and electrical conductivity (EC), were recorded according to the protocol of Kim and Park [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. After 24 hours of air drying at 35\u0026deg;C, the dry soil samples were crushed and sieved through 2 mm mesh. Isolation was performed utilizing soil particles with diameters between 0.1 and 2 \u0026micro;m. For enrichment, nine milliliters of sterile distilled water was added to one gram of sieved soil. After serial dilutions to 10⁻⁴, 50 \u0026micro;L of each dilution level was added to starch nitrate agar, and the plates were incubated for seven days at 30\u0026deg;C [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. The resulting colonies were then purified and examined further.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003e2.2. Morphological identification\u003c/h2\u003e \u003cp\u003eThe morphological characteristics, including texture, aerial mycelium, substrate mycelium, growth rate, and pigmentation on starch-nitrate media, were analyzed. Shiriling and Gottlieb [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e] observed that the colours of the aerial and reverse cultures were analyzed under standard lighting conditions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e2.3. Molecular identification\u003c/h2\u003e \u003cp\u003e \u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain BA1 was cultured on starch-nitrate broth medium at 30\u0026deg;C, with shaking at 150 rpm for 7 days. Cultures were centrifuged at 3000 rpm for 20 min and the resulted pellet was used for the extraction of genomic DNA using EZ-10 Spin Column Bacterial Genomic DNA Miniprep Kits. \u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain BA1 was partially sequenced by the 16S region. The 16S rDNA regions were amplified using the universal forward primer 27F 5\u0026rsquo;-AGAGTTTGATC (AC) TGGCTCAG\u0026ndash;3\u0026rsquo;) and the reverse primer 1492R (5\u0026rsquo;-ACGG (CT) TACCTTGTTACGACTT-3\u0026rsquo;). The components and cycle conditions were controlled as described by Al-Dhabi et al [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. The PCR reactions consisted of 4 \u0026micro;l of dNTPs (1.0 mM each, Roche, Penzberg, Germany), 2 \u0026micro;l of 10X buffer (Roche), 0.2 \u0026micro;l of each primer (0.5 \u0026micro;g), 0.2 \u0026micro;l of Taq polymerase (5 U/\u0026micro;l), 1 \u0026micro;l of 50 ng of template DNA, and sterile Milli-Q water in a final volume of 19.8 \u0026micro;l. The amplification conditions started by an initial denaturation at 94\u0026deg;C for 3 min, followed by 30 cycles of 94\u0026deg;C for 30 s, 50\u0026deg;C for 30 s, and 72\u0026deg;C for 1 min, and a final extension at 72\u0026deg;C for 7 min. The PCR-fragments were purified using the Qiagen PCR-purification kit (Qiagen, Hilden, Germany). The PCR products were examined by electrophoresis in a 1.5% agarose gel, stained with ethidium bromide, and visualized under UV transilluminator. The 16S rRNA genes of \u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain BA1 was sequenced using the forward 27F primer and the Big Dye Terminator Cycle Sequencing kit v1.1. Sequencing reactions were run via the Applied Biosystems a 3500xL Genetic Analyzer, Foster city, California. The resulted nucleotide sequences were aligned throughout the GeneBank data, the BLAST-N program (Basic Local Alignment Search Tool-Nucleotides) from the NCBI website (National Center for Biotechnology Information).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e2.4. Exploring the antibacterial potential of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1\u003c/h2\u003e \u003cp\u003eTwo serious pathogens, \u003cem\u003eEscherichia coli\u003c/em\u003e and \u003cem\u003eKlebsiella pneumoniae\u003c/em\u003e, were graciously acquired from the Microbial Biotechnology Unit at the Faculty of Science, Kafrelsheikh University. One ml of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 spore suspension was inoculated into 50 ml of autoclaved starch-nitrate broth medium, cultured in a 250 ml Erlenmeyer flask. The culture was agitated at 30\u0026deg;C and 120 rpm for duration of 7 days. After the incubation period, the upper culture fluid was separated from \u003cem\u003eS. cavourensis\u003c/em\u003e biomass by centrifugation at 3,000 g for 20 min. To test the inhibitory effect, fresh nutrient agar plates were evenly inoculated with 1 ml of 18-h culture broth of the respective test bacterial pathogens [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. 5 mm diameter holes were punched in each prepared plate using a sterile cork punch. Each hole was filled with 100 \u0026micro;l of filtered upper culture fluid from \u003cem\u003eS. cavourensis\u003c/em\u003e strain NRRL 2740. The plates were incubated for 24 h at 37\u0026deg;C. The width of the inhibition zone was then measured in mm [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e2.5. Partial purification of antibacterial compounds\u003c/h2\u003e \u003cp\u003eCultured \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 was utilized as inoculum for one litre of culture broth. The culture was grown for 7 days at 30\u0026deg;C and 120 rpm in a shaking incubator (Thermo MaxQ 445). The biomass of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 assembly using Whatman No. 1 filter paper, and the supernatant was centrifuged at 8,000 \u0026times; g for 15 min at 4\u0026deg;C to reach a clear (filtered) solution [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. The supernatant was then aseptically transferred to 250-ml conical flasks and treated with equal volumes (1:1, v/v) of n-butanol, ethyl acetate, and diethyl ether, respectively. The mixture was shaken vigorously for 20 min, followed by a 15-minute stand-off for phase separation. The aqueous and organic phases were separately concentrated at 40\u0026deg;C to evaporate the solvents and obtain a viscous crude extract. The residue was dried in a vacuum dryer to completely remove any residual solvents, weighed, and dissolved in 1 mg/ml methanol for the agar diffusion test. Each experiment used methanol as a control for dangerous bacteria. The best solvent was employed to extract antibacterial compounds [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. A rotating evaporator (Heidolph, Germany) concentrated organic and aqueous phases to near dryness under reduced pressure.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e2.6. Evaluation of cytotoxic effect of ethyl acetate extract\u003c/h2\u003e \u003cp\u003eThe cytotoxicity of an ethyl acetate extract of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 was studied in African green monkey kidney cells (VERO) according to the protocol of Mosmann [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] and Gomha et al [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e2.7. GC-MS analysis of ethyl acetate extract\u003c/h2\u003e \u003cp\u003eBioactive compounds from the ethyl acetate extract of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 were identified using gas chromatography-mass spectrometry (GC-MS). The analysis was performed using an Agilent 7890A GC system connected to an Agilent 5975C MS detector. A HP-5MS column (30 m \u0026times; 250 \u0026micro;m \u0026times; 0.25 \u0026micro;m) was used. Helium was used as the carrier gas at a constant flow rate of 1.5 mL/min. The oven temperature was increased according to the following program: 1 min at 90\u0026deg;C, then gradually increased at 8\u0026deg;C/min to 300\u0026deg;C, followed by a 30-minute stabilization phase. One microliter of sample was injected in splitless mode at an injector temperature of 290\u0026deg;C. The mass spectrometer operated at ionization energy of 70 electron volts and covered a mass range of 60 to 600 atomic mass units [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e2.8. Bactericidal potential of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 filtrate\u003c/h2\u003e \u003cp\u003eA growth inhibition investigation was done to examine the bactericidal activity of the filtrate from \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 against two multidrug resistant pathogens, \u003cem\u003eK. pneumoniae\u003c/em\u003e and \u003cem\u003eE. coli\u003c/em\u003e. Approximately 500 \u0026micro;l of the filtrate was added to 9 ml of nutrient broth medium and inoculated with 500 \u0026micro;l of the bacterial suspensions (1 \u0026times; 10⁵ CFU ml⁻\u0026sup1;), then incubated at 37\u0026deg;C for 24 h in a shaker incubator set to 150 rpm. All treatments were conducted in triplicate [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Control cultures were augmented with 500 \u0026micro;l of NB media in lieu of the filtrate from the \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1. Bacterial growth was assessed by quantifying the turbidity of the cultures using a JASCO V-730 UV-Visible Spectrophotometer at 600 nm [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e2.9. Scanning electron microscopy (SEM) of bacterial cells\u003c/h2\u003e \u003cp\u003eScanning electron microscopy (SEM) was used to observe and detect the alterations in the morphological properties of \u003cem\u003eE. coli\u003c/em\u003e and \u003cem\u003eK. pneumoniae\u003c/em\u003e in both control and treatment cultures. Cells for scanning electron microscopy (SEM) were prepared as follows: Cell pellets from treated and untreated bacteria were collected by centrifugation (12,000 g, 1 min). Each pellet was resuspended in 500 \u0026micro;L of phosphate-buffered saline (PBS, pH 7) containing 2% formaldehyde and 1% glutaraldehyde, then centrifuged again. The pellet was then washed twice with distilled water and resuspended in 1 mL distilled water. A 5-\u0026micro;L aliquot of this suspension was placed on a 5 mm \u0026times; 5 mm silicon wafer and air-dried at room temperature [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The dried samples were examined using a field-emission scanning electron microscope (FE-SEM, JEOL JSM-IT200).\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec12\" class=\"Section2\"\u003e \u003ch2\u003e2.10. Statistical analysis\u003c/h2\u003e \u003cp\u003eAll experiments were performed three times independently (n\u0026thinsp;=\u0026thinsp;3). Data are presented as mean\u0026thinsp;\u0026plusmn;\u0026thinsp;standard error of the mean. Statistical analysis was performed using SPSS (Statistical Package for the Social Sciences) software [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e].\u003c/p\u003e \u003c/div\u003e"},{"header":"3. Results","content":"\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e \u003ch2\u003e3.1. Identification of \u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain BA1\u003c/h2\u003e \u003cdiv id=\"Sec15\" class=\"Section3\"\u003e \u003ch2\u003e3.1.1. Morphological characteristics\u003c/h2\u003e \u003cp\u003eThe isolate exhibited a chalky appearance, pale yellow aerial mycelium, buff substrate mycelium, and little brown pigmentation (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e). The substrate mycelium of colonies was observable within 2 days of incubation. The emergence of colonies between the third and fifth day resembles a standard bacterial colony. Verification of an actinomycetal colony may be achieved by examining the colony's powdery texture. The colonies are firmly adhered to the agar surface, much to a plant anchored in soil.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec16\" class=\"Section3\"\u003e \u003ch2\u003e3.1.2. Molecular identification (16S rRNA gene sequence analysis)\u003c/h2\u003e \u003cp\u003eThe PCR-amplified 16S rRNA gene was 1500 bp (Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e2\u003c/span\u003e). The Foster City, California-based Applied Biosystems 3500xL Genetic Analyser was used to purify and sequence the amplified DNA. Sequence comparison to the National Center for Biotechnology Information database showed that the isolate is a member of the genus \u003cem\u003eStreptomyces\u003c/em\u003e of the family Streptomycetaceae (phylum Actinobacteria). NCBI GenBank (Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e) showed 100% similarity with \u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain PES4. MUSCLE was used to match the sequence with 12 closely related \u003cem\u003eStreptomyces\u003c/em\u003e species. Kumar et al [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] used MEGA-X software to merge their NCBI GenBank sequences for Neighbour-Joining phylogenetic analysis and Kimura 2-parameter evolutionary distance calculations. The phylogenetic tree (Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e3\u003c/span\u003e) confirmed the isolate's resemblance to \u003cem\u003eS. cavourensis\u003c/em\u003e strain PES4. The partial 16S rRNA gene sequence of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 has GenBank entry number PX588109.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003e\u003cb\u003eGene sequence alignments of 16S rRNA gene of the isolate\u003c/b\u003e \u003cb\u003eStreptomyces cavourensis\u003c/b\u003e \u003cb\u003estrain BA1 to the data available at NCBI (BLASTN)\u003c/b\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eDescription\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMax Score\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eTotal Score\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eQuery Cover\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eE value\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePer. Ident\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAccession\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain PES4 16S ribosomal RNA gene, partial sequence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1242\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1242\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eOM909163.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain A-2 16S ribosomal RNA gene, partial sequence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e99.85%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eKC178676.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eStreptomyces araujoniae\u003c/em\u003e strain HSA312 16S ribosomal RNA gene, partial sequence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e99.85%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eMN902069.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eKitasatospora albolonga\u003c/em\u003e strain NBRC 13465 16S ribosomal RNA, partial sequence\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c4\"\u003e \u003cp\u003e100%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c6\"\u003e \u003cp\u003e99.85%\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eNR_041144.1\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003c/div\u003e \u003cdiv id=\"Sec17\" class=\"Section2\"\u003e \u003ch2\u003e3.2. Antibacterial activity\u003c/h2\u003e \u003cp\u003eTable\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig5\" class=\"InternalRef\"\u003e4\u003c/span\u003e highlight the potent antibacterial effects of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 filtrate, with ethyl acetate organic extract emerging as a promising candidate for further exploration. The pathogen-specific responses suggest selective activity, warranting additional studies on compound isolation and potential synergistic formulations. \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 filtrate exhibited strong antibacterial effects, with inhibition zones up to 31 mm for \u003cem\u003eK. pneumoniae\u003c/em\u003e and 23 mm for \u003cem\u003eE. coli\u003c/em\u003e. Among the fractionated extracts, the ethyl acetate organic phase has demonstrated the highest inhibition against both pathogens, \u003cem\u003eK. pneumoniae\u003c/em\u003e (24 mm) and \u003cem\u003eE. coli\u003c/em\u003e (20 mm). While the ethyl acetate aqueous phase displayed relatively weak activity, suggesting that fewer active compounds are extracted into this phase. On the other hand, the n-butanol organic phase showed moderate inhibition of 11 mm for \u003cem\u003eE. coli\u003c/em\u003e and 15 mm for \u003cem\u003eK. pneumoniae\u003c/em\u003e, indicating selective antimicrobial properties.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eAntibacterial Activity of \u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain BA1 (mm). Zones of inhibition produced by the filtrate, aqueous layer, and organic fractions (n-butanol, ethyl acetate, diethyl ether) against \u003cem\u003eKlebsiella pneumoniae\u003c/em\u003e and \u003cem\u003eEscherichia coli\u003c/em\u003e\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\"\u0026plusmn;\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003ePathogen\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"7\" nameend=\"c8\" namest=\"c2\"\u003e \u003cp\u003eInhibition zone (mm)\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cb\u003eS. cavourensis\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003efiltrate\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cb\u003eN-butanol\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eorganic phase\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cb\u003eN-butanol\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eaqueous phase\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cb\u003eEthyl acetate\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eorganic phase\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cb\u003eEthyl acetate\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eaqueous phase\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cb\u003eDiethyl ether\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eorganic phase\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003e\u003cb\u003eDiethyl ether\u003c/b\u003e\u003c/p\u003e \u003cp\u003e\u003cb\u003eaqueous phase\u003c/b\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eE. coli\u003c/em\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e23\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e20\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.1\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cem\u003eK. pneumonia\u003c/em\u003ee\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c2\"\u003e \u003cp\u003e31\u0026thinsp;\u0026plusmn;\u0026thinsp;0.4\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c3\"\u003e \u003cp\u003e18\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c4\"\u003e \u003cp\u003e9\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c5\"\u003e \u003cp\u003e24\u0026thinsp;\u0026plusmn;\u0026thinsp;0.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c6\"\u003e \u003cp\u003e8\u0026thinsp;\u0026plusmn;\u0026thinsp;0.3\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c7\"\u003e \u003cp\u003e13\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\"\u0026plusmn;\" colname=\"c8\"\u003e \u003cp\u003e11\u0026thinsp;\u0026plusmn;\u0026thinsp;0.2\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003ctfoot\u003e \u003ctr\u003e\u003ctd colspan=\"8\"\u003e* Means with \u0026plusmn;\u0026thinsp;Standard errors\u003c/td\u003e\u003c/tr\u003e \u003c/tfoot\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec18\" class=\"Section2\"\u003e \u003ch2\u003e3.3. Cytotoxic evaluation\u003c/h2\u003e \u003cp\u003eCytotoxicity examination of ethyl acetate extract of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 on the VERO cell line is shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig6\" class=\"InternalRef\"\u003e5\u003c/span\u003e. Recorded data illustrated a moderate impact with a CC50 value of 296.1 \u0026micro;g/ml. The extract displays a safe profile for normal cells. Obtained data strongly recommend using it in medical applications for its potential safety advantages.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec19\" class=\"Section2\"\u003e \u003ch2\u003e3.4. GC-MS Analysis\u003c/h2\u003e \u003cp\u003eGiven its significant antibacterial activity against the studied pathogens, the ethyl acetate extract of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 was analyzed using gas chromatography-mass spectrometry (GC-MS). Comparison of the spectra with the National Institute of Standards and Technology (NIST) database confirmed the presence of five bioactive compounds with antibacterial activity (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e). As shown in Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, the most abundant compounds were the 9,12-octadecadienoic acid derivative (Z,Z)-TMS (21.5% of the peak area) and the palmitic acid derivative-TMS (19.6%). In addition, linoelaidic acid, trimethylsilyl ester (6.6%), bis (2-ethylhexyl) phthalate (3.8%), and methyl 10,12-heptadecadiynoate (3.0%) were detected. The GC-MS profile (Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e) visually supports the quantitative data from Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e, confirming the presence and relative abundance of bioactive compounds. Peak area percentages from Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e correspond well with peak intensities in Fig.\u0026nbsp;\u003cspan refid=\"Fig7\" class=\"InternalRef\"\u003e6\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eIdentified bioactive compounds detected by GC-mass spectroscopy of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 ethyl acetate extract\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"8\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c8\" colnum=\"8\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\"\u003e \u003cp\u003eN\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003eName of the compound\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003eMolecular formula\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003eMolecular weight\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003eRetention time\u003c/p\u003e \u003cp\u003e(Min)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003ePeak area (%)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003eActivity\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c8\"\u003e \u003cp\u003eReference\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e1\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eMethyl 10,12-heptadecadiynoate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u003csub\u003e18\u003c/sub\u003eH\u003csub\u003e28\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e276\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e4.22\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.0\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAntibacterial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e]33[\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e2\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003ePalmitic Acid, TMS derivative\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u003csub\u003e19\u003c/sub\u003eH\u003csub\u003e40\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eSi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e328\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e28.90\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e19.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAntimicrobial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e]31[\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e3\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003e9,12-Octadecadienoic acid (Z,Z)-,TMS derivative\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e40\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eSi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e352\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e31.70\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e21.5\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAntimicrobial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e]30[\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e4\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eLinoelaidic acid, trimethylsilyl ester\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u003csub\u003e21\u003c/sub\u003eH\u003csub\u003e40\u003c/sub\u003eO\u003csub\u003e2\u003c/sub\u003eSi\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e352\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e31.97\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e6.6\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAntibacterial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e]32[\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e\u003cb\u003e5\u003c/b\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c2\"\u003e \u003cp\u003eBis (2-ethylhexyl) phthalate\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c3\"\u003e \u003cp\u003eC\u003csub\u003e24\u003c/sub\u003eH\u003csub\u003e38\u003c/sub\u003eO\u003csub\u003e4\u003c/sub\u003e\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e390\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e36.62\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e3.8\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c7\"\u003e \u003cp\u003eAntibacterial\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"left\" colname=\"c8\"\u003e \u003cp\u003e]34[\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003e3.5. Bactericidal potentiality of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1\u003c/h2\u003e \u003cp\u003eScanning electron microscopy (SEM) images offer definitive visual proof of the antibacterial activities of the \u003cem\u003eS. cavourensis\u003c/em\u003e filtrate (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003e). The picture of untreated \u003cem\u003eE. coli\u003c/em\u003e (control group) has the characteristic rod shape, exhibiting a smooth surface and intact cellular structure, signifying healthy, unmodified cells (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ea). Conversely, Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003eb illustrates considerable structural damage, characterized by irregularities, with several surface cells exhibiting dents, wrinkles, or fractures. Indicators of membrane rupture, shrinkage, or surface roughness are apparent in \u003cem\u003eE. coli\u003c/em\u003e subjected to the filtrate. The untreated \u003cem\u003eKlebsiella pneumoniae\u003c/em\u003e (control group) displays a capsule-like morphology with smooth contours, while the treated strain demonstrates pronounced morphological alterations, including cell wall breakdown or collapse and considerable elongation relative to the control cells. Additionally, other cells exhibited pronounced wrinkles and curvatures, with some cellular debris indicating potential leakage of cell contents due to membrane rupture (Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ec, Fig.\u0026nbsp;\u003cspan refid=\"Fig8\" class=\"InternalRef\"\u003e7\u003c/span\u003ed).\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"4. Discussion","content":"\u003cp\u003eThis work isolated the \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 from the Zubaida fish farm, situated southwest of Lake Burullus in Egypt, a distinctive habitat with potential for novel microbial discoveries. Morphological and molecular analyses verified its classification within the phylum Actinobacteria, family Streptomycetaceae, and genus \u003cem\u003eStreptomyces\u003c/em\u003e, demonstrating a 100% similarity to \u003cem\u003eS. cavourensis\u003c/em\u003e strain PES4 and a 99.85% to both \u003cem\u003eStreptomyces araujoniae\u003c/em\u003e strain HSA312 and \u003cem\u003eKitasatospora albolonga\u003c/em\u003e strain NBRC 13465 in NCBI GenBank. According to Silva et al [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e], \u003cem\u003eStreptomyces araujoniae\u003c/em\u003e has white aerial mycelium with no production of diffusible pigments on starch nitrate agar. Bergey's Manual of Systemic Bacteriology [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] states that \u003cem\u003eKitasatospora albolonga\u003c/em\u003e exhibits beige colonies and is characterized by an absence of melanin synthesis. Our strain, \u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain BA1 (PX588109), exhibited pale yellow aerial mycelium and produced melanin pigments on SNA media. The filtrate of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 exhibited significant bactericidal effect against investigated pathogens, \u003cem\u003eK. pneumoniae\u003c/em\u003e and \u003cem\u003eE. coli\u003c/em\u003e. The ethyl acetate organic phase had the greatest inhibitory efficacy among the solvent extracts. \u003cem\u003eK. pneumoniae\u003c/em\u003e and \u003cem\u003eE. coli\u003c/em\u003e exhibited significant sensitivity to the filtrate, although shown reduced sensitivity to the solvent fractions. The elevated inhibitory zones noted in the filtrates corroborate the concept that many bioactive components function synergistically [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Conversely, the ethyl acetate aqueous phase exhibited the least inhibition, indicating reduced quantities or diminished solubility of the bioactive compounds. Cytotoxicity is a fundamental aspect of antibacterial research. Numerous effective antibacterial drugs demonstrate cytotoxic effects on eukaryotic cells [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. This study's cytotoxicity assessment revealed a moderate impact on the VERO cell line, with CC50 values of 296.1 \u0026micro;g/ml for the ethyl acetate extract. The results demonstrate that \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 extracts had a positive safety profile, hence augmenting their potential for medical applications. Gas chromatography-mass spectrometry analysis of the ethyl acetate extract confirmed the presence of four effective antibacterial fatty acids: 9,12-octadecadienoic acid (Z,Z)-, a TMS derivative (21.5%), palmitic acid, a TMS derivative (19.6%), linoleic acid, a trimethylsilyl ester (6.6%) and methyl 10,12-heptadecadinoate (3.0%). Furthermore, bis(2-ethylhexyl) phthalate was identified at a concentration of 3.8%. Numerous prior studies demonstrated that these chemicals exhibit significant antibacterial activity against various Gram-positive and Gram-negative microorganisms.\u003c/p\u003e \u003cp\u003eGas chromatography-mass spectrometry (GC-MS) analysis of the ethyl acetate extract of \u003cem\u003eStreptomyces\u003c/em\u003e sp. MMM2 identified four active fatty acids: 9,12-octadecadienoic acid (PUA) exhibited antibacterial activity against various pathogenic bacteria, including \u003cem\u003eStaphylococcus aureus\u003c/em\u003e (\u003cem\u003eS. aureus\u003c/em\u003e) and \u003cem\u003eEscherichia coli\u003c/em\u003e [\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e]. Palmitic acid, a saturated fatty acid, exhibited remarkable antibacterial activity against several pathogens, such as \u003cem\u003eK. pneumoniae\u003c/em\u003e and \u003cem\u003eP. aeruginosa\u003c/em\u003e [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. Linoleic acid, an omega-6 trans-unsaturated fatty acid, isolated from watermelon seed oil, exhibited antibacterial activity against both Gram-positive and Gram-negative bacteria [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Methyl 10,12-heptadecadinoate, a saturated fatty acid from \u003cem\u003ePiper longum\u003c/em\u003e, exhibits bactericidal activity against multidrug-resistant \u003cem\u003eSalmonella\u003c/em\u003e strains [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. Furthermore, bis(2-ethylhexyl) phthalate from \u003cem\u003eLactobacillus plantarum\u003c/em\u003e has shown antibacterial activity against \u003cem\u003eEscherichia coli\u003c/em\u003e and \u003cem\u003eStaphylococcus aureus\u003c/em\u003e [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eThe SEM images of the morphology of \u003cem\u003eE. coli\u003c/em\u003e cells treated with the filtrate of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 exhibited irregularities, with certain surface cells appearing dented, wrinkled, or fractured. Moreover, the delineation of the cell wall boundary was ambiguous in several cells. Conversely, the treated \u003cem\u003eK. pneumoniae\u003c/em\u003e cells exhibited notable abnormalities in comparison to the control cells. Other cells exhibited pronounced creases and curvatures, with some cellular debris indicating potential leakage, perhaps due to the degradation of cell membranes and the subsequent efflux of cellular contents. Chouhan et al [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e] assert that the hydrophobic characteristics of oils facilitate their penetration into the lipid bilayers of bacterial cell membranes, hence disturbing their integrity and enhancing permeability, resulting in the leakage of ions and cellular contents. Saturated fatty acids, including palmitic acid and methyl 10,12-heptadecadiynoate, are thought to compromise bacterial cell membranes, perhaps leading to cell lysis or disruption of essential biological processes [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e]. Yoon et al [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e] discovered that unsaturated fatty acids, including 9,12-octadecadienoic acid, can infiltrate bacterial cell membranes, modifying their structure and function, which leads to cell death and the release of intracellular contents. Furthermore, the enzyme enoyl-acyl carrier protein reductase (FabI), crucial for bacterial fatty acid synthesis, can be blocked by specific unsaturated fatty acids, including linoleic acid. This disruption of fatty acid synthesis may inhibit bacterial growth and survival [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. Moreover, the antibacterial efficacy of the oil fluctuates based on the specific bacterial strain and the type of oil analyzed. Consequently, growth suppression may result from multiple components functioning synergistically [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. This corroborates our findings that the filtrate of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 exhibited superior antibacterial activity against the investigated pathogens compared to any other solvent fraction.\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis work reports the initial isolation of the brackish actinomycete strain \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 from the brackish sediments of the Zubaida fish farm, situated southwest of Lake Burullus in Egypt. The isolate was characterized by morphological and molecular methods. Its filtrate consistently yielded larger inhibitory zones than fractionated solvents, indicating that several bioactive chemicals function synergistically within the whole filtrate. The ethyl acetate organic phase had significant action. Ethyl acetate extract has demonstrated moderate cytotoxic effects on the VERO cell line, suggesting possible safety attributes. The GC-MS spectra of the ethyl acetate extract verified the existence of five bioactive components. Four of these were potent antibacterial fatty acids. Furthermore, bis(2-ethylhexyl) phthalate was identified. The SEM images of the morphology of \u003cem\u003eE. coli\u003c/em\u003e cells treated with \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 filtrate exhibited irregularities, with some surface cells appearing dented, wrinkled, or fractured. The treated \u003cem\u003eK. pneumoniae\u003c/em\u003e cells exhibited considerable elongation in comparison to the control cells. Other cells exhibited pronounced creases and curvatures, accompanied by cell debris indicative of membrane rupture and the subsequent efflux of cellular contents. The results validate the substantial bactericidal effectiveness of fatty acids from \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 in conjunction with naturally occurring antimicrobial agents and encourage future exploration of the \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 as a potential source of bioactive compounds to address antibiotic resistance.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgments\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to the study conception. BA, RE and EE designed experiments. Material preparation BA, RE and EE. Statistical analysis and figures preparation were performed by BA. EE, RE and HA supervised the work. All authors commented on the 1st version of the manuscript. All authors read and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNo fund was received during this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData generated during the current study are available in the supplementary file. Sequence data that support the findings of this study have been deposited in the NCBI’s Sequence Read Archive under accession number PX588109.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting interests\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no competing interests.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor details\u0026nbsp;\u003c/strong\u003e\u003c/p\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eBasma M. Atallah, Hamdy Agwa, and Eithar El-Mohsnawy\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eMicrobial Biotechnology Unit, Botany and Microbiology Department, Faculty of Science, Kafrelsheikh University, Kafrelsheikh, 33516, Egypt\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eBasma M. Atallah[0009-0008-9435-5510]\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eHamdy E. Agwa [0009-0004-2739-9012]\u003c/li\u003e\n \u003cli\u003eEithar El-Mohsnawy[0000-0002-0060-3421]\u003c/li\u003e\n\u003c/ul\u003e\n\u003cul type=\"disc\"\u003e\n \u003cli\u003e\u003cstrong\u003eRamadan El-domany\u003c/strong\u003e\u003c/li\u003e\n\u003c/ul\u003e\n\u003cp\u003eMicrobiology and Immunology Department, Faculty of Pharmacy, Kafrelsheikh University, Kafrelsheikh, 33516, Egypt\u003c/p\u003e\n\u003cul\u003e\n \u003cli\u003eRamadan El-domany [https://orcid.org/0000-0001-6817-0151]\u003c/li\u003e\n\u003c/ul\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBarka A, Vatsa P, Sanchez L, Gaveau-Vaillant N, Jacquard C, Meier-Kolthoff P, Klenk P, Cl\u0026eacute;ment C, Ouhdouc Y, Van Wezel P. Taxonomy, Physiology, and natural products of actinobacteria. Microbiology and Molecular Biology Reviews 2016; 9:80. https://doi.org/10.1128/mmbr.00044-16. \u003c/li\u003e\n\u003cli\u003eDe Simeis D, Serra S. Actinomycetes: a never-ending source of bioactive compounds\u0026mdash;an overview on antibiotics production. Antibiotics 2021; 10:483. https://doi.org/10.3390/antibiotics10050483.\u003c/li\u003e\n\u003cli\u003eKhan S, Gul A, Jehan S, Khan Z, Saeed J, Shirazi R, Raziq A, Waseem M, Ullah H. Biodiversity of actinomycetes and their secondary metabolites: A Comprehensive Review. Journal of advanced Biomedical and Pharmaceutical Sciences 2023; 6:36-48. https://doi.org/10.21608/jabps.2022.161607.1165. \u003c/li\u003e\n\u003cli\u003eRammali S, Hilali L, Dari K, Bencharki B, Rahim A, Timinouni M, Gaboune F, El Aalaoui M, Khattabi A. Antimicrobial and antioxidant activities of \u003cem\u003eStreptomyces\u003c/em\u003e species from soils of three different cold sites in the Fez-Meknes region Morocco. Scientific Reports 2022;12:17233. https://doi.org/10.1038/s41598-022-21644-z. \u003c/li\u003e\n\u003cli\u003eAtallah B, El-Mohsnawy E, El-shouny W, Haroun S. Identification and characterization of different potentially antibacterial compounds from a marine \u003cem\u003eStreptomyces\u003c/em\u003e sp. Sp1. Journal of Animal and Plant Sciences 2023;33:166-173. https://doi.org/10.36899/japs.2023.1.0605. \u003c/li\u003e\n\u003cli\u003eHassan M, El Sersy A, Abdelwahab S, Ali R. Statistical optimization and valuable applications of bioactive compounds produced by marine \u003cem\u003ePseudoalteromonas piscicida\u003c/em\u003e. J. Appl. Pharm. Sci 2017;84-93. https://doi.org/10.7324/japs.2017.71012. \u003c/li\u003e\n\u003cli\u003eNessim R, Tadros H, Moawad M, El-Sayed A, Deghady E, Abou Taleb A. Major constituents\u0026rsquo; distribution as an indicator of water exchange between lake Burullus and the Mediterranean Sea. Blue Econ; 2024; 2:3. https://doi.org/10.57241/2805-2994.1017. \u003c/li\u003e\n\u003cli\u003eZhou L, Feng S, Sun G, Tang B, Zhu X, Song K, Zhang X, Lu H, Liu H, Sun Z. Extensively drug-resistant Gram-negative bacterial bloodstream infection in hematological disease Infect. Drug Resist 2019;12:481. 10.2147/IDR.S191462\u003c/li\u003e\n\u003cli\u003eNgamcharungchit C, Chaimusik N, Panbangred W, Euanorasetr J. Intra bioactive metabolites from terrestrial and marine actinomycetes. Molecules 2023; 28:5915. https://doi.org/10.3390/molecules28155915. \u003c/li\u003e\n\u003cli\u003eKim N, Park H. Monitoring of soil EC for the prediction of soil nutrient regime under different soil water and organic matter contents. Appl. Biol. Chem 2024;67:1. https://doi.org/10.1186/s13765-023-00849-4.\u003c/li\u003e\n\u003cli\u003eAhmad S, El \u0026ndash;Gendy O, Ahmed R, Hassan M, El \u0026ndash;Kabbany M, Merdash G. Exploring the antimicrobial and antitumor potentials of \u003cem\u003eStreptomyces \u003c/em\u003esp. AGM12-1 isolated from Egyptian soil. Front. Microbiol 2017; 8:438. https://doi.org/ 10.3389/fmicb.2017.00438. \u003c/li\u003e\n\u003cli\u003ePrashanthi R, et al. Isolation, characterization, and molecular identification of soil bacteria showing antibacterial activity against human pathogenic bacteria J. Genet. Eng. Biotechnol 2021;18:19-120. https://doi.org/10.1186/s43141-021-00219-x. \u003c/li\u003e\n\u003cli\u003eShirling B, Gottlieb D. Methods for Characterization of\u003cem\u003e Streptomyces \u003c/em\u003eSpecies. Int.J. Syst Bacterial 1966; 6(3):13-340. https://doi.org/10.1099/00207713-16-3-313. \u003c/li\u003e\n\u003cli\u003eAl-Dhabi N, Esmail G, Duraipandiyan V, Valan Arasu M, Salem-Bekhit M. Isolation, identification and screening of antimicrobial thermophilic \u003cem\u003eStreptomyces\u003c/em\u003e sp. Al-Dhabi-1 isolated from Tharban hot spring, Saudi Arabia. Extremophiles 2016; 20:79-90. https://doi.org/10.1007/s00792-015-0799-1. \u003c/li\u003e\n\u003cli\u003eAtallah B, Haroun S, El-Mohsnawy E. Antibacterial activity of two actinomycetes species isolated from black sand in North Egypt. South African Journal of Science 2023;119:11-12. https://doi.org/10.17159/sajs.2023/14509 \u003c/li\u003e\n\u003cli\u003eSathiyanarayanan G, Gandhmathi R, Sabarathnan B, SeghalKiran G, Selvin J. Optimization and production of pyrrolidon antimicrobial agent from marine sponge-associated \u003cem\u003eStreptomyces\u003c/em\u003e sp. MAPSIS. Bioprocess. Biosyst. Eng 2014; 37:561-573. https://doi.org/10.1007/s00449-013-1023-2. \u003c/li\u003e\n\u003cli\u003eHolmalahti J, Von Wright A, Raatikainen O. Variations in the spectra of biological activities of actinomycetes isolated from different soils. Lett. Appl. Microbiol 1994;18:144-146. https://doi.org/10.1111/j.1472-765x.1994.tb00829.x. \u003c/li\u003e\n\u003cli\u003eMosmann T. Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays. Immunol. Methods 1983; 65:55-63. https://doi.org/10.1016/0022-1759(83)90303-4. \u003c/li\u003e\n\u003cli\u003eGomha M, Riyadh M, Mahmmoud A, Elaasser M. Synthesis and anticancer activities of Thiazoles, 1,3-Thiazines, and Thiazolidine Using Chitosan-Grafted-Poly(vinylpyridine) as Basic Catalyst. Heterocycles 2015;91:1227-1243. https://doi.org/10.3987/com-15-13210. \u003c/li\u003e\n\u003cli\u003eHassan S, Shobier A. GC/MS identification and applications of bioactive seaweed extracts from Mediterranean coast of Egypt. EJABF 2018;5:1-21. https://doi.org/10.21608/ejabf.2018.17952. \u003c/li\u003e\n\u003cli\u003eHamouda R, Hussein H, Abo-elmagd A, et al\u003cem\u003e. \u003c/em\u003eSynthesis and biological characterization of silver nanoparticles derived from the cyanobacterium \u003cem\u003eOscillatoria limnetica.\u003c/em\u003e Sci. Rep 2019;13071. https://doi.org/10.1038/s41598-019-49444-y. \u003c/li\u003e\n\u003cli\u003eEl-Mohsnawy E, El-Shaer A, El-Gharabawy F, et al. Assignment of the antibacterial potential of Ag2O/ZnO nanocomposite against MDR bacteria \u003cem\u003eProteus mirabilis\u003c/em\u003e and \u003cem\u003eSalmonella typhi\u003c/em\u003e isolated from bone marrow transplant patients. Braz. J. Microbiol 2023; 54:2807-2815. https://doi.org/10.1007/s42770-023-01138-4.\u003c/li\u003e\n\u003cli\u003eNaskar A, Lee S, Kim K. Easy one-pot low-temperature synthesized Ag-ZnO nanoparticles and their activity against clinical isolates of methicillin-resistant \u003cem\u003eStaphylococcus aureus\u003c/em\u003e. Front. Bioeng. Biotechnol 2020;8:216. https://doi.org/10.3389/fbioe.2020.00216. \u003c/li\u003e\n\u003cli\u003eLorowitz W, Saxton E, Sondossi M, Nakaoka K. Integrating statistics with a microbiology laboratory activity. Microbiol. Educ 2005; 6:14-19. https://doi.org/10.1128/me.6.1.14-19.2005. \u003c/li\u003e\n\u003cli\u003eKumar S, Stecher G, Tamura K. MEGA7: Molecular Evolutionary Genetics Analysis Version 7.0 for Bigger Datasets. Mol. Biol. Evol 2016; 33:1870-4. https://doi.org/10.1093/molbev/msw054. \u003c/li\u003e\n\u003cli\u003eSilva L, et al. Streptomyces araujoniae sp. nov.: An actinomycete isolated from a potato tubercle. Antonie-van-Leeuwenhoek 2013; 103:6. https://doi.org/10.1007/s10482-013-9901-9.\u003c/li\u003e\n\u003cli\u003eBergey\u0026apos;s Manual of Systematic Bacteriology The Actinobacteria. New York: Springer 2012. https://doi.org/10.1007/978-0-387-68233-4_3.\u003c/li\u003e\n\u003cli\u003eHassan G, Abdel-Monem O, Sleem A,et al. Antimicrobial, antibiofilm, cytotoxicity, and anti-DNA topoisomerase activity of \u003cem\u003eStreptomyces\u003c/em\u003e sp. 22SH with ADME and in silico study. BMC Microbiol 2025;25:219. https://doi.org/10.1186/s12866-025-03912-w. \u003c/li\u003e\n\u003cli\u003eZipperer A, Kretschmer D. Cytotoxicity assays as predictors of the safety and efficacy of antimicrobial agents Methods. Mol. Biol 2017; 1520:107-118. https://doi.org/10.1007/978-1-4939-6634-96. \u003c/li\u003e\n\u003cli\u003eMalash M, et al. Antimicrobial Activities of a Novel Marine \u003cem\u003eStreptomyces\u003c/em\u003e sp. MMM2 Isolated from El- Arish coast, Egypt. Egyptian Journal of Aquatic Biology and Fisheries 2022; 26:1317-1339. https://doi.org/10.21608/ejabf.2022.268783. \u003c/li\u003e\n\u003cli\u003eJoujou M, Darra E, Rajha N, et al. Evaluation of synergistic/antagonistic antibacterial activities of fatty oils from apricot, date, grape, and black seeds. Sci. Rep 2024; 14:6532. https://doi.org/10.1038/s41598-024-54850-y. \u003c/li\u003e\n\u003cli\u003eSoliman M, Abdel-Wahhab A. Synthesis of antibacterial bioactive compounds using linoleic acid extracted from Melon seeds oil and evaluation of its waste meal ash for fried oil regeneration .Waste Biomass Valor 2024; 15:487-499. https://doi.org/10.1007/s12649-023-02161-0. \u003c/li\u003e\n\u003cli\u003eRawat P, et al. Antibacterial, antioxidant, and phytochemical analysis of \u003cem\u003ePiper longum\u003c/em\u003e fruit extracts against multi-drug resistant non-typhoidal \u003cem\u003eSalmonella \u003c/em\u003estrains in vitro. Journal of Applied and Natural Science 2022; 14:1225-1239. https://doi.org/10.31018/jans.v14i4.3774. \u003c/li\u003e\n\u003cli\u003eJaved R, Salman M, Tariq A, Tawab A, Zahoor K, Naheed S, Shahid M, Ijaz A, Ali H. The antibacterial and larvicidal potential of bis-(2-Ethylhexyl) phthalate from \u003cem\u003eLactiplantibacillus plantarum\u003c/em\u003e. Molecules 2022;27:7220. https://doi.org/10.3390/molecules27217220. \u003c/li\u003e\n\u003cli\u003eChouhan S, Sharma K, Guleria S. Antimicrobial activity of some essential oils-present status and future perspectives. Medicines (Basel) 2017;4:58. https://doi.org/10.3390/medicines4030058. \u003c/li\u003e\n\u003cli\u003eArellano H, Nardello-Rataj V, Szunerits S, Boukherroub R, Fameau L. Saturated long chain fatty acids as possible natural alternative antibacterial agents: Opportunities and challenges Adv. Colloid. Interface. Sci 2023; 318:102952. https://doi.org/10.1016/j.cis.2023.102952. \u003c/li\u003e\n\u003cli\u003eYoon K, Jackman A, Valle-Gonz\u0026aacute;lez R, Cho J. Antibacterial free fatty acids and monoglycerides: biological activities, experimental testing, and therapeutic applications. Int. J. Mol. Sci 2018; 19:1114. https://doi.org/10.3390/ijms19041114. \u003c/li\u003e\n\u003cli\u003eBatistel F, Gonzalez O, Sears A, Khan U, de Souza J. Palmitic acid alone or combined with stearic and oleic enhances ruminal fiber degradation and alters microbiome composition. Front. Microbiol 2025;16:1624738. https://doi.org/10.3389/fmicb.2025.1624738.\u003c/li\u003e\n\u003cli\u003eAtta S, Waseem D, Fatima H, Naz I, Rasheed F, Kanwal N. Antibacterial potential and synergistic interaction between natural polyphenolic extracts and synthetic antibiotic on clinical isolates Saudi. J. Biol. Sci 2023;3:103576. https://doi.org/10.1016/j.sjbs.2023.103576. \u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"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":"bactericidal potential, cytotoxicity, fatty acids, SEM, Streptomyces cavourensis","lastPublishedDoi":"10.21203/rs.3.rs-8124036/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8124036/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eAntibiotic-resistant microorganisms pose a significant danger to civilization, particularly due to the lack of current effective antibiotics. This work included the isolation and identification of \u003cem\u003eStreptomyces cavourensis\u003c/em\u003e strain BA1 (PX588109) by morphological and molecular characterization. The filtrate of the \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 showed significant antibacterial efficacy against two multidrug-resistant pathogens, \u003cem\u003eEscherichia coli\u003c/em\u003e and \u003cem\u003eKlebsiella pneumoniae\u003c/em\u003e. The ethyl acetate organic phase had the greatest inhibitory efficacy among the solvent extracts. GC-MS spectra revealed the presence of several potent antibacterial compounds: 9,12-Octadecadiens (Z,Z) TMS-derivate, Palmitins TMS-derivate, Linoleates trimethylsilyl ester, and Methyl-10,12-heptadecadienoleate. The cytotoxicity assessment prove that the oil toxins produced by ethyl acetate extracts are considered moderately safe for the kidney of African Green Monkey (VERO cell line), with CC50 values of 296.1 \u0026micro;g/ml. The findings demonstrate that \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 extracts had a positive safety profile, hence augmenting their potential for medicinal applications. The SEM images of \u003cem\u003eE. coli\u003c/em\u003e cells treated with the filtrate of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 exhibited irregularities, with some surface cells appearing dented, wrinkled, or fractured. The treated \u003cem\u003eK. pneumoniae\u003c/em\u003e cells exhibited notable elongation in comparison to the control cells. Other cells exhibited pronounced creases and curvatures, with some cellular debris indicating potential leakage of cellular contents due to membrane rupture. These results underscore the significant bactericidal potential of fatty acids when combined with naturally occurring antimicrobial agents and facilitate future investigation of \u003cem\u003eS. cavourensis\u003c/em\u003e strain BA1 as a unique ideal source of bioactive chemicals to address antibiotic resistance.\u003c/p\u003e","manuscriptTitle":"Evaluating the antibacterial activity and safety of bioactive compounds extracted from a brackish water Streptomyces cavourensis strain BA1","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-12-16 01:07:46","doi":"10.21203/rs.3.rs-8124036/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":"3ce2306b-9290-4b43-90ae-169bd2859423","owner":[],"postedDate":"December 16th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2026-02-25T07:26:58+00:00","versionOfRecord":[],"versionCreatedAt":"2025-12-16 01:07:46","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8124036","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8124036","identity":"rs-8124036","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}