Metagenomic insights into microbial community structure in arsenic-rich shallow and deep groundwater

Microorganisms dwelling in arsenic-rich groundwater have a pivotal role in biogeochemical cycles and are expected to have significant influence on the cycle of arsenic, a metalloid responsible for severe water pollution and the causing agent of the worst mass poisoning in human history. To gain insight into the indigenous bacterial population in arsenic-rich shallow and deep groundwater and to cover a greater genetic diversity, we conducted a 454 pyrosequencing study targeting nine defined hyper-variable regions of 16S rDNAs. The results revealed the presence of diverse and unequal bacterial communities mostly represented by the genera Acinetobacter, Herbaspirillum, Bacillus, Flavisolibacter, Massilia, Nitrospira, Symbiobacterium, Bellilinea, Arthrobacter, Undibacterium, Sphingomonas, Geobacter, Delftia, Pseudomonas, Hydrogenophaga, Paenibacillus, Gemmatimonas, Anaeromyxobacter, Rheinheimera and Rhodococcus. Overall observations suggest that the indigenous bacteria in arsenic-rich groundwater possess adequate catabolic ability to mobilize arsenic by a cascade of reactions mostly linked to bacterial nutrient acquisitions and detoxification.