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Functional genotyping of Sulfurospirillum spp. in mixed cultures allowed the identification of a new tetrachloroethene reductive dehalogenase.

ABSTRACT: Reductive dehalogenases are the key enzymes involved in the anaerobic respiration of organohalides such as the widespread groundwater pollutant tetrachloroethene. The increasing number of available bacterial genomes and metagenomes gives access to hundreds of new putative reductive dehalogenase genes that display a high level of sequence diversity and for which substrate prediction remains very challenging. In this study, we present the development of a functional genotyping method targeting the diverse reductive dehalogenases present in Sulfurospirillum spp., which allowed us to unambiguously identify a new reductive dehalogenase from our tetrachloroethene-dechlorinating SL2 bacterial consortia. The new enzyme, named PceATCE, shows 92% sequence identity with the well-characterized PceA enzyme of Sulfurospirillum multivorans, but in contrast to the latter, it is restricted to tetrachloroethene as a substrate. Its apparent higher dechlorinating activity with tetrachloroethene likely allowed its selection and maintenance in the bacterial consortia among other enzymes showing broader substrate ranges. The sequence-substrate relationships within tetrachloroethene reductive dehalogenases are also discussed.

SUBMITTER: Buttet GF

PROVIDER: S-EPMC3811552 | biostudies-literature | 2013 Nov

REPOSITORIES: biostudies-literature

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Functional genotyping of Sulfurospirillum spp. in mixed cultures allowed the identification of a new tetrachloroethene reductive dehalogenase.

Buttet Géraldine F GF Holliger Christof C Maillard Julien J

Applied and environmental microbiology 20130830 22

Reductive dehalogenases are the key enzymes involved in the anaerobic respiration of organohalides such as the widespread groundwater pollutant tetrachloroethene. The increasing number of available bacterial genomes and metagenomes gives access to hundreds of new putative reductive dehalogenase genes that display a high level of sequence diversity and for which substrate prediction remains very challenging. In this study, we present the development of a functional genotyping method targeting the ...[more]

PMID: 23995945

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Project description:Organohalide respiration (OHR) is a bacterial anaerobic process in which halogenated compounds, e.g. tetrachloroethene (PCE), are used as terminal electron acceptors. Our model organisms are Dehalobacter restrictus strain PER-K23, an obligate OHR bacterium, and Desulfitobacterium hafniense strain TCE1, a bacterium with a versatile energy metabolism. The key catalytic enzyme is the tetrachloroethene reductive dehalogenase (PceA) that is, at genomic level, encoded in a highly conserved gene cluster (pceABCT) in both D. restrictus and D. hafniense strain TCE1. To date, the functions of PceA and PceT, a dedicated molecular chaperone for the maturation of PceA, are well defined. However, the role of PceB and PceC are still not elucidated. Here, we present a multilevel study aiming at deciphering the stoichiometry of the pceABCT individual gene products. The investigation was assessed at RNA level by reverse transcription and (quantitative) polymerase chain reaction, while at protein level, proteomic analyses based on parallel reaction monitoring were performed to quantify the PceA, B, C and T proteins in cell-free extracts as well as in soluble and membrane fractions of both strains using heavy-labelled reference peptides. At RNA level, our results confirmed the co-transcription of all pce gene products, while the quantitative analysis revealed a relative stoichiometry of the gene transcripts of pceA, pceB, pceC and pceT at approximately 1.0:3.0:0.1:0.1 in D. restrictus. This trend was not observed in D. hafniense strain TCE1, where no substantial difference was measured for the four genes. At proteomic level, a 2:1 stoichiometry of PceA and PceB was observed in the membrane fraction, and a low abundance of PceC in comparison to the other two proteins. In the soluble fraction, a 1:1 stoichiometry of PceA and PceT was identified. In summary, we show that the pce gene cluster is transcribed as an operon with, however, a level of transcription that differs for individual genes, an observation that could be explained by post-transcriptional events, such as RNA processing and differential RNA stability. Results at protein level suggest that PceA and PceB form a membrane-bound PceA2B protein complex, which, in contrast to the proposed model, seems to be devoid of PceC.

Dataset Information

Functional genotyping of Sulfurospirillum spp. in mixed cultures allowed the identification of a new tetrachloroethene reductive dehalogenase.

Publications

Functional genotyping of Sulfurospirillum spp. in mixed cultures allowed the identification of a new tetrachloroethene reductive dehalogenase.

Similar Datasets

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