Variable response of arsenic contaminated groundwater microbial community to electron acceptor regime revealed by microcosm based high-throughput sequencing approach

Abstract

Arsenic (As) mobilization in alluvial aquifers is facilitated by microbially catalyzed redox transformations that depend on the availability of electron acceptors (EAs). In this study, the response of an As-contaminated groundwater microbial community from West Bengal, India towards varied EAs was elucidated through microcosm based 16S rRNA gene amplicon sequencing. Acinetobacter, Deinococcus, Nocardioides, etc., and several unclassified bacteria (Ignavibacteria) and archaea (Bathyarchaeia, Micrarchaeia) previously not reported from As-contaminated groundwater of West Bengal, characterized the groundwater community. Distinct shifts in community composition were observed in response to various EAs. Enrichment of operational taxonomic units (OTUs) affiliated to Denitratisoma (NO₃ˉ), Spirochaetaceae (Mn⁴⁺), Deinococcus (As⁵⁺), Ruminiclostridium (Fe³⁺), Macellibacteroides (SO₄²ˉ), Holophagae-Subgroup 7 (HCO₃ˉ), Dechloromonas and Geobacter (EA mixture) was noted. Alternatively, As³⁺ amendment as electron donor allowed predominance of Rhizobium. Taxonomy based functional profiling highlighted the role of chemoorganoheterotrophs capable of concurrent reduction of NO₃ˉ, Fe³⁺, SO₄²ˉ, and As biotransformation in As-contaminated groundwater of West Bengal. Our analysis revealed two major aspects of the community, (a) taxa selective toward responding to the EAs, and (b) multifaceted nature of taxa appearing in abundance in response to multiple substrates. Thus, the results emphasized the potential of microbial community members to influence the biogeochemical cycling of As and other dominant anions/cations.

Keywords:

• Microbial diversity
• engal delta plain
• 16S rRNA gene
• taxa recruitment
• functional potential
• As-metabolizing bacteria
• arsenite oxidase

Acknowledgement

The authors are thankful to the Department of Science and Technology, Government of India (Water Technology Initiative-DST/TM/WTI/2K15/182) for funding the project. The Next-generation sequencing facility used in this work was created by PS through the IIT Kharagpur SGBSI challenge grant (IIT/SRIC/BT/ODM/2015-16/141). AS thanks the Department of Science and Technology, Government of India, as well as IIT Kharagpur for providing fellowship and BM acknowledges the Department of Science and Technology, Government of India for providing INSPIRE Fellowship (DST/INSPIRE Fellowship/2012/763/IF120832).

Conflicts of interest

The authors declare no conflicts of interest.

Declarations

Ethics approval and consent to participate

Not applicable

Consent for publication

Not applicable

Availability of data and materials

The amplicon sequences corresponding to each sample from this study were deposited under the accession number PRJNA649362 in NCBI as Sequence read archive (SRA). The functional gene sequences are submitted in NCBI under the accession number MT506015-MT506023.

Authors' contributions

Conceived and designed the experiments: PS SKK. Performed the experiments: AS. Analyzed the data: AS PS. Contributed reagents/materials/analysis tools: PS SKK. Wrote the paper: PS AS BM SKK. Site selection, field operation and to understand the results obtained: PS AS BM SKK.

Additional information

Funding

This research was supported by grants from the Department of Science and Technology, Government of India (Water Technology Initiative-DST/TM/WTI/2K15/182) and the IIT Kharagpur SGBSI challenge grant (IIT/SRIC/BT/ODM/2015-16/141).