Characterization of arsenite-oxidizing bacteria isolated from arsenic-contaminated groundwater of West Bengal
2014
Paul, Dhiraj | Poddar, Soumya | Sar, Pinaki
Nine arsenic (As)-resistant bacterial strains isolated from As-rich groundwater samples of West Bengal were characterized to elucidate their potential in geomicrobial transformation and bioremediation aspects. The 16S rRNA gene-based phylogenetic analysis revealed that the strains were affiliated with genera Actinobacteria , Microbacterium , Pseudomonas and Rhizobium . The strains exhibited high resistance to As [Minimum inhibitory concentration (MIC) ≥ 10 mM As ³⁺ and MIC ≥ 450 mM As ⁵⁺] and other heavy metals, e.g., Cu ²⁺, Cr ²⁺, Ni ²⁺, etc. (MIC ≥ 2 mM) as well as As transformation (As ³⁺ oxidation and As ⁵⁺ reduction) capabilities. Their ability to utilize diverse carbon source(s) including hydrocarbons and different alternative electron acceptor(s) (As ⁵⁺, SO ₄²⁻, S ₂O ₃²⁻, etc.) during anaerobic growth was noted. Growth at wide range of pH, temperature and salinity, production of siderophore and biofilm were observed. Together with these, growth pattern and transformation kinetics indicated a high As ³⁺ oxidation activity of the isolates Rhizobium sp. CAS934i, Microbacterium sp. CAS905i and Pseudomonas sp. CAS912i. A positive relation between high As ³⁺ resistance and As ³⁺ oxidation and the supportive role of As ³⁺ in bacterial growth was noted. The results highlighted As ³⁺ oxidation process and metabolic repertory of strains indigenous to contaminated groundwater and indicates their potential in As ³⁺ detoxification. Thus, such metabolically well equipped bacterial strains with highest As ³⁺ oxidation activities may be used for bioremediation of As contaminated water and effluents in the near future.
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