Isolation and Characterization of Copper Tolerant Bacterial Species Habituating in Copper Mines and Study of Their Potentiality as a Plant Growth Stimulator

Copper (Cu) is a vital micronutrient for all living organisms below its toxicity limit. Various industrial activities, mining deposits, excessive use of harmful chemicals, waste discharges, and drugs are the main reason for the emerging copper concentration. Emphases of the current study were to isolate and characterize highly copper-tolerating bacterial (CTB) species from a copper-contaminated site. In enrichment culture techniques, 24 copper tolerant microbial isolates were evaluated and the maximum tolerable concentration (MTC) was determined using various concentrations of copper sulfate pentahydrate (CuSO4.5H2O) solution. Three bacterial strains named GKSM2, GKSM6, and GKSM11 were tolerant to 350 mg/l of CuSO4.5H2O. The 16S rRNA gene sequencing and phylogeny data revealed that these CTB belong to species Bacillus zanthoxyli , Bacillus stercoris , and Pseudomonas alcaliphila species. CTB showed their optimized growth at moderate salt concentration (0.1-0.5M NaCl), temperature range (20-45˚C) and wide pH range (pH 5.0-11). All the strains can produce various Plant growth stimulating (PGS) traits viz ., phytohormones (IAA, GA), proline, nitrogen fixation, ammonification, and antioxidant enzymes in presence and absence of Cu 2+ stress. The result displays that adsorption of Cu 2+ ions evidenced by TEM, SEM, and SEM-EDX analysis.