Diversity of arsenite oxidizing bacterial communities in arsenic-rich deltaic aquifers in West Bengal, India

Abstract

High arsenic (As) concentration in groundwater has affected human health, particularly in South-East Asia putting millions of people at risk. Biogeochemical cycling of As carried out by different bacterial groups are suggested to control the As fluxes in aquifers. A functional diversity approach in link with As precipitation was adopted to study bacterial community structures and their variation within the As contaminated Bengal Delta Plain (BDP) aquifers of India. Groundwater samples collected from two shallow aquifers in Karimpur II (West Bengal, India), during years 2010 and 2011, were investigated to trace the effects immediately after monsoon period (precipitation) on community structure and diversity of bacterial assemblages with a focus on arsenite oxidizing bacterial phyla for two successive years. The study focused on amplification, clone library generation and sequencing of the arsenite oxidase large sub-unit gene aioA and 16S rRNA marker, with respect to changes in elemental concentrations. New set of primers were designed to amplify the aioA gene as a phylogenetic marker to study taxonomically diverse arsenite oxidizing bacterial groups in these aquifers. The overall narrow distribution of bacterial communities based on aioA and 16S rRNA sequences observed was due to poor nutrient status and anoxic conditions in these As contaminated aquifers. Proteobacteria was the dominant phylum detected, within which Acidovorax, Hydrogenophaga, Albidiferax, Bosea, and Polymorphum were the major arsenite oxidizing bacterial genera based on the number of clones sequenced. The structure of bacterial assemblages including those of arsenite oxidizing bacteria seems to have been affected by increase in major elemental concentrations (e.g., As, Fe, S, and Si) within two sampling sessions, which was supported by statistical analyses. One of the significant findings of this study is detection of novel lineages of 16S rRNA-like bacterial sequences indicating presence of indigenous bacterial communities BDP wells that can play important role in biogeochemical cycling of elements including As.

Sub-surface Biogeochemical Characteristics and Its Effect on Arsenic Cycling in the Holocene Gray Sand Aquifers of the Lower Bengal Basin

“…It clearly indicated the complex carbon sources of BDP has a role in sustaining and supporting only specific microbial communities. Such natural selection of microbial communities in the BDP groundwaters correlate with increasing As concentration pointing toward the putative role of microbial communities in As mobilization and distribution (Ghosh et al, 2014).…”

“…In this study, sediments were collected from two boreholes installed next to the two GSA wells, referred hereafter, as wells 28 (N Ghosh et al, 2014) in Karimpur II block located in Nadia district, West Bengal (Figure 1). Arsenic concentration in these wells ranged from 64 to 131 µg/l and microbial communities in the groundwater were associated with biogeochemical cycling of As and Fe (Ghosh et al, 2014).…”

“…Arsenic concentration in these wells ranged from 64 to 131 µg/l and microbial communities in the groundwater were associated with biogeochemical cycling of As and Fe (Ghosh et al, 2014). Well 28 is located in the backyard of a farmer's house and the groundwater from this well is used as a potable supply for drinking water in the household.…”

Functions and Unique Diversity of Genes and Microorganisms Involved in Arsenite Oxidation from the Tailings of a Realgar Mine

“…Until now, the aioA genes have been identified from more than 80 genera of bacteria and archaebacteria, which were isolated from various arsenic-contaminated environments. Most of the aioA genes belong to Alphaproteobacteria, Betaproteobacteria, or Gammaproteobacteria (31)(32)(33)(34)36). However, little is known about the microbial diversity and functional features of AOB from the tailings of a realgar mine that are characteristic of high concentrations of arsenic and sulfate.…”

“…The aioA gene is usually used as a valuable molecular marker for investigations of the diversity, evolution, and potential activity of AOB (22,29). Recent studies based on metagenomic DNA extracted from soils, sediments, water, minerals, tailings, and geothermal mats with different chemical characteristics and various levels of arsenic contamination suggested that the diversities of AioA proteins differ considerably among these sampling sites (29)(30)(31)(32)(33)(34)(35)(36)(37). Until now, the aioA genes have been identified from more than 80 genera of bacteria and archaebacteria, which were isolated from various arsenic-contaminated environments.…”