Metagenome based analysis of groundwater from arsenic contaminated sites of West Bengal revealed community diversity and their metabolic potential

The study of microbial community in groundwater systems is considered to be essential to improve our understanding of arsenic (As) biogeochemical cycling in aquifers, mainly as it relates to the fate and transport of As. The present study was conducted to determine the microbial community composition and its functional potential using As-contaminated groundwater from part of the Bengal Delta Plain (BDP) in West Bengal, India. Geochemical analyses indicated low to moderate dissolved oxygen (0.42-3.02 mg/L), varying As (2.5-311 µg/L) and Fe (0.19-1.2 mg/L) content, while low concentrations of total organic carbon (TOC), total inorganic carbon (TIC), nitrate, and sulfate were detected. <i>Proteobacteria</i> was the most abundant phylum, while the indiscriminate presence of an array of archaeal phyla, <i>Euryarchaeota</i>, <i>Crenarchaeota</i>, <i>Nanoarchaeota</i>, etc., was noteworthy. The core community members were affiliated to <i>Sideroxydans, Acidovorax, Pseudoxanthomonas, Brevundimonas,</i> etc. However, diversity assessed over multiple seasons indicated a shift from <i>Sideroxydans</i> to <i>Pseudomonas</i> or <i>Brevundimonas</i> dominant community, suggestive of microbial response to seasonally fluctuating geochemical stimuli. Taxonomy-based functional potential showed prospects for As biotransformation, methanogenesis, sulfate respiration, denitrification, etc. Thus, this study strengthened existing reports from this region by capturing the less abundant or difficult-to-culture taxa collectively forming a major fraction of the microbial community.