Diversity of Betaproteobacteria revealed by novel primers suggests their role in arsenic cycling.

High arsenic concentration in groundwater is a severe environmental problem affecting human health, particularly in countries of South and South-East Asia. The Bengal Delta Plain (BDP) distributed within India and Bangladesh is a major arsenic-affected region where groundwater is the primary source of drinking water. Previous studies have indicated that members of the bacterial class constitute a major fraction of the microbial community in many of the aquifers within this region. Bacteria belonging to this class are known to be involved in redox cycling of arsenic as well as other metals such iron and manganese, thereby impacting arsenic mobilization and immobilization. While microbial diversity in arsenic-contaminated environments is generally assessed using universal 16S rRNA gene primers, targeted evaluation of Betaproteobacteria diversity remains poorly constrained. In this study, bacterial diversity was investigated in the groundwater from two shallow aquifers (West Bengal, India) based on 16S rRNA gene clone libraries and sequencing using a custom-designed pair of primers specific to . Specificity of the primers was confirmed as well as by the absence of PCR amplification of other bacterial classes. Four major families (, , and ) were detected among which members of represented 59% and 71% of the total community in each aquifer. The four OTUs (operational taxonomic units; 97% sequence identity) within were close phylogenetic relatives of bacteria within the genus known to solubilize phosphate minerals. Additionally, the OTUs belonging to were closely related to the members of the genera and , known to oxidize iron under microaerophilic conditions. These results suggest that members of can potentially influence iron and phosphorus cycling which can influence biogeochemistry in arsenic-contaminated aquifers of the BDP.