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BioMed Research International
Volume 2017 (2017), Article ID 9191086, 12 pages
https://doi.org/10.1155/2017/9191086
Research Article

Identification of Multiple Dehalogenase Genes Involved in Tetrachloroethene-to-Ethene Dechlorination in a Dehalococcoides-Dominated Enrichment Culture

1Department of Environmental Engineering and Architecture, Graduate School of Environmental Studies, Nagoya University, Chikusa, Nagoya 464-8601, Japan
2Department of Civil Engineering, Nagoya Institute of Technology, Showa, Nagoya 466-8555, Japan
3Department of Civil Engineering, Graduate School of Engineering, Nagoya University, Chikusa, Nagoya 464-8603, Japan
4Institute of Materials and Systems for Sustainability (IMaSS), Nagoya University, Chikusa, Nagoya 464-8601, Japan

Correspondence should be addressed to Naoko Yoshida; pj.ca.hcetin@okoan.adihsoy

Received 30 March 2017; Accepted 3 July 2017; Published 15 August 2017

Academic Editor: Raluca M. Hlihor

Copyright © 2017 Mohamed Ismaeil et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Chloroethenes (CEs) are widespread groundwater toxicants that are reductively dechlorinated to nontoxic ethene (ETH) by members of Dehalococcoides. This study established a Dehalococcoides-dominated enrichment culture (designated “YN3”) that dechlorinates tetrachloroethene (PCE) to ETH with high dechlorination activity, that is, complete dechlorination of 800 μM PCE to ETH within 14 days in the presence of Dehalococcoides species at  copies of 16S rRNA gene/mL. The metagenome of YN3 harbored 18 rdhA genes (designated YN3rdhA1–18) encoding the catalytic subunit of reductive dehalogenase (RdhA), four of which were suggested to be involved in PCE-to-ETH dechlorination based on significant increases in their transcription in response to CE addition. The predicted proteins for two of these four genes, YN3RdhA8 and YN3RdhA16, showed 94% and 97% of amino acid similarity with PceA and VcrA, which are well known to dechlorinate PCE to trichloroethene (TCE) and TCE to ETH, respectively. The other two rdhAs, YN3rdhA6 and YN3rdhA12, which were never proved as rdhA for CEs, showed particularly high transcription upon addition of vinyl chloride (VC), with and mRNA copies per gene, respectively, suggesting their possible functions as novel VC-reductive dehalogenases. Moreover, metagenome data indicated the presence of three coexisting bacterial species, including novel species of the genus Bacteroides, which might promote CE dechlorination by Dehalococcoides.