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Diversity, metabolic properties and arsenic mobilization potential of indigenous bacteria in arsenic contaminated groundwater of West Bengal, India.

ABSTRACT: Arsenic (As) mobilization in alluvial aquifers is caused by a complex interplay of hydro-geo-microbiological activities. Nevertheless, diversity and biogeochemical significance of indigenous bacteria in Bengal Delta Plain are not well documented. We have deciphered bacterial community compositions and metabolic properties in As contaminated groundwater of West Bengal to define their role in As mobilization. Groundwater samples showed characteristic high As, low organic carbon and reducing property. Culture-independent and -dependent analyses revealed presence of diverse, yet near consistent community composition mostly represented by genera Pseudomonas, Flavobacterium, Brevundimonas, Polaromonas, Rhodococcus, Methyloversatilis and Methylotenera. Along with As-resistance and -reductase activities, abilities to metabolize a wide range carbon substrates including long chain and polyaromatic hydrocarbons and HCO3, As3+ as electron donor and As5+/Fe3+ as terminal electron acceptor during anaerobic growth were frequently observed within the cultivable bacteria. Genes encoding cytosolic As5+ reductase (arsC) and As3+ efflux/transporter [arsB and acr3(2)] were found to be more abundant than the dissimilatory As5+ reductase gene arrA. The observed metabolic characteristics showed a good agreement with the same derived from phylogenetic lineages of constituent populations. Selected bacterial strains incubated anaerobically over 300 days using natural orange sand of Pleistocene aquifer showed release of soluble As mostly as As3+ along with several other elements (Al, Fe, Mn, K, etc.). Together with the production of oxalic acid within the biotic microcosms, change in sediment composition and mineralogy indicated dissolution of orange sand coupled with As/Fe reduction. Presence of arsC gene, As5+ reductase activity and oxalic acid production by the bacteria were found to be closely related to their ability to mobilize sediment bound As. Overall observations suggest that indigenous bacteria in oligotrophic groundwater possess adequate catabolic ability to mobilize As by a cascade of reactions, mostly linked to bacterial necessity for essential nutrients and detoxification.

SUBMITTER: Paul D

PROVIDER: S-EPMC4370401 | biostudies-literature | 2015

REPOSITORIES: biostudies-literature

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Diversity, metabolic properties and arsenic mobilization potential of indigenous bacteria in arsenic contaminated groundwater of West Bengal, India.

Paul Dhiraj D Kazy Sufia K SK Gupta Ashok K AK Pal Taraknath T Sar Pinaki P

PloS one 20150323 3

Arsenic (As) mobilization in alluvial aquifers is caused by a complex interplay of hydro-geo-microbiological activities. Nevertheless, diversity and biogeochemical significance of indigenous bacteria in Bengal Delta Plain are not well documented. We have deciphered bacterial community compositions and metabolic properties in As contaminated groundwater of West Bengal to define their role in As mobilization. Groundwater samples showed characteristic high As, low organic carbon and reducing proper ...[more]

PMID: 25799109

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Project description: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.

Project description:BackgroundIn this study a large random collection (n=2188) of facultative oligotrophic bacteria, from 90 water samples gathered in three consecutive years (2007-2009) from three different sampling sites of River Mahananda in Siliguri, West Bengal, India, were investigated for the presence of class 1 integrons and sequences of the amplification products.Methodology/principal findingsReplica plating method was employed for determining the antibiotic resistance profile of the randomly assorted facultative oligotrophic isolates. Genomic DNA from each isolate was analyzed by PCR for the presence of class 1 integron. Amplicons were cloned and sequenced. Numerical taxonomy and 16S rRNA gene sequence analyses were done to ascertain putative genera of the class 1 integron bearing isolates. Out of 2188 isolates, 1667 (76.19%) were antibiotic-resistant comprising of both single-antibiotic resistance (SAR) and multiple-antibiotic resistant (MAR), and 521 (23.81%) were sensitive to all twelve different antibiotics used in this study. Ninety out of 2188 isolates produced amplicon(s) of varying sizes from 0.15 to 3.45 KB. Chi-square (χ(2)) test revealed that the possession of class 1 integron in sensitive, SAR and MAR is not equally probable at the 1% level of significance. Diverse antibiotic-resistance gene cassettes, aadA1, aadA2, aadA4, aadA5, dfrA1, dfrA5, dfrA7, dfrA12, dfrA16, dfrA17, dfrA28, dfrA30, dfr-IIe, blaIMP-9, aacA4, Ac-6'-Ib, oxa1, oxa10 and arr2 were detected in 64 isolates. The novel cassettes encoding proteins unrelated to any known antibiotic resistance gene function were identified in 26 isolates. Antibiotic-sensitive isolates have a greater propensity to carry gene cassettes unrelated to known antibiotic-resistance genes. The integron-positive isolates under the class Betaproteobacteria comprised of only two genera, Comamonas and Acidovorax of family Comamonadaceae, while isolates under class Gammaproteobacteria fell under the families, Moraxellaceae, Pseudomonadaceae, Aeromonadaceae and Enterobacteriaceae.ConclusionsOligotrophic bacteria are good sources of novel genes as well as potential reservoirs of antibiotic resistance gene casettes.

Dataset Information

Diversity, metabolic properties and arsenic mobilization potential of indigenous bacteria in arsenic contaminated groundwater of West Bengal, India.

Publications

Diversity, metabolic properties and arsenic mobilization potential of indigenous bacteria in arsenic contaminated groundwater of West Bengal, India.

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