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A comparative genomics and reductive dehalogenase gene transcription study of two chloroethene-respiring bacteria, Dehalococcoides mccartyi strains MB and 11a.

ABSTRACT: Genomes of two trichloroethene (TCE)-respiring Dehalococcoides (Dhc) mccartyi, strains MB and 11a, were sequenced to identify reductive dehalogenases (RDase) responsible for oraganohalide respiration. Transcription analyses were conducted to verify the roles of RDase subunit A genes (rdhA) in chloroethene respiration. Some interesting features of the strain MB draft genome include a large genome size, two CRISPR-cas type I systems, and 38 rdhA genes. Strain 11a has a stream-lined genome with 11 rdhA genes, of which nine are distinct. Quantitative real-time PCR transcription analysis of RDase gene transcripts showed that a single RDase gene, designated mbrA, was up-regulated upon exposure to TCE and no other RDase genes were considerably expressed in strain MB. A single RDase gene, designated vcrA, was up-regulated upon exposure to TCE and expressed at a steady level until all chloroethenes were completely dechlorinated to ethene at 147?h in strain 11a. Overall, this study reports the genomes of two distinct Dhc strains; both contain numerous uncharacterized RDase genes, but in each strain only one such gene was expressed highly during organohalide respiration.

SUBMITTER: Low A

PROVIDER: S-EPMC4635342 | biostudies-literature | 2015 Nov

REPOSITORIES: biostudies-literature

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A comparative genomics and reductive dehalogenase gene transcription study of two chloroethene-respiring bacteria, Dehalococcoides mccartyi strains MB and 11a.

Low Adrian A Low Adrian A Shen Zhiyong Z Cheng Dan D Rogers Matthew J MJ Lee Patrick K H PK He Jianzhong J

Scientific reports 20151106

Genomes of two trichloroethene (TCE)-respiring Dehalococcoides (Dhc) mccartyi, strains MB and 11a, were sequenced to identify reductive dehalogenases (RDase) responsible for oraganohalide respiration. Transcription analyses were conducted to verify the roles of RDase subunit A genes (rdhA) in chloroethene respiration. Some interesting features of the strain MB draft genome include a large genome size, two CRISPR-cas type I systems, and 38 rdhA genes. Strain 11a has a stream-lined genome with 11 ...[more]

PMID: 26541266

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Project description:Dehalococcoides mccartyi strains are corrinoid-auxotrophic Bacteria and axenic cultures that require vitamin B12 (CN-Cbl) to conserve energy via organohalide respiration. Cultures of D. mccartyi strains BAV1, GT and FL2 grown with limiting amounts of 1 µg l(-1) CN-Cbl quickly depleted CN-Cbl, and reductive dechlorination of polychlorinated ethenes was incomplete leading to vinyl chloride (VC) accumulation. In contrast, the same cultures amended with 25 µg l(-1) CN-Cbl exhibited up to 2.3-fold higher dechlorination rates, 2.8-9.1-fold increased growth yields, and completely consumed growth-supporting chlorinated ethenes. To explore whether known cobamide-producing microbes supply Dehalococcoides with the required corrinoid cofactor, co-culture experiments were performed with the methanogen Methanosarcina barkeri strain Fusaro and two acetogens, Sporomusa ovata and Sporomusa sp. strain KB-1, as Dehalococcoides partner populations. During growth with H2/CO2, M. barkeri axenic cultures produced 4.2 ± 0.1 µg l(-1) extracellular cobamide (factor III), whereas the Sporomusa cultures produced phenolyl- and p-cresolyl-cobamides. Neither factor III nor the phenolic cobamides supported Dehalococcoides reductive dechlorination activity suggesting that M. barkeri and the Sporomusa sp. cannot fulfil Dehalococcoides' nutritional requirements. Dehalococcoides dechlorination activity and growth occurred in M. barkeri and Sporomusa sp. co-cultures amended with 10 µM 5',6'-dimethylbenzimidazole (DMB), indicating that a cobalamin is a preferred corrinoid cofactor of strains BAV1, GT and FL2 when grown with chlorinated ethenes as electron acceptors. Even though the methanogen and acetogen populations tested did not produce cobalamin, the addition of DMB enabled guided biosynthesis and generated a cobalamin that supported Dehalococcoides' activity and growth. Guided cobalamin biosynthesis may offer opportunities to sustain and enhance Dehalococcoides activity in contaminated subsurface environments.

Dataset Information

A comparative genomics and reductive dehalogenase gene transcription study of two chloroethene-respiring bacteria, Dehalococcoides mccartyi strains MB and 11a.

Publications

A comparative genomics and reductive dehalogenase gene transcription study of two chloroethene-respiring bacteria, Dehalococcoides mccartyi strains MB and 11a.

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