Molecular analysis of microbial community in arsenic-rich groundwater of Kolsor, West Bengal

ABSTRACT

Bacterial community composition within the highly arsenic (As) contaminated groundwater from Kolsur, West Bengal was analyzed over a period of 3 years using 16S rRNA gene clone library and Denaturing Gradient Gel Electrophoresis (DGGE). Molecular phylogenetic study revealed abundance of α-Proteobacteria (56%) and Firmicutes (29%) along with members of β-Proteobacteria, Verrucomicrobia and Sphingobacteria as relatively minor groups. Along with consistent physicochemical environment, a stable microbial community structure comprising of bacterial genera Agrobacterium-Rhizobium, Ochrobactrum, Pseudomonas, Anoxybacillus and Penibacillus was recorded over the three years study period. Presence of cytosolic arsenate reductase (arsC) gene was observed within the microbial community. Phylogenetic analyses revealed that all the arsC sequences were closely related to the same gene from γ-proteobacterial members while the community was consisted of mainly α-proteobacterial groups. Such phylogenetic incongruence between 16S rRNA and arsC genes possibly indicated horizontal gene transfer (HGT) of the ars genes within the groundwater community. Overall, the study reported a nearly stable geomicrobial environment and genetic determinant related to As homeostasis gene, and provided a better insight on biogeochemistry of As contaminated aquifer of West Bengal.

KEYWORDS:

• Arsenic
• bacterial community
• 16S rRNA gene
• arsC
• ARDRA
• DGGE

Acknowledgments

The authors acknowledge the kind help of Mr. Buddha Deb Banerjee, Barasat, North 24 Parganas, West Bengal during sampling of As-contaminated groundwater.

Funding

The authors acknowledge financial support from Council of Scientific and Industrial Research (CSIR) Government of India [38(1314)/11/EMR-II]. Angana Sarkar and Dhiraj Paul acknowledge IIT Kharagpur and University Grants Commission, New Delhi, respectively for doctoral fellowship.