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Genetics and molecular biology of the electron flow for sulfate respiration in desulfovibrio.

ABSTRACT: Progress in the genetic manipulation of the Desulfovibrio strains has provided an opportunity to explore electron flow pathways during sulfate respiration. Most bacteria in this genus couple the oxidation of organic acids or ethanol with the reduction of sulfate, sulfite, or thiosulfate. Both fermentation of pyruvate in the absence of an alternative terminal electron acceptor, disproportionation of fumarate and growth on H(2) with CO(2) during sulfate reduction are exhibited by some strains. The ability to produce or consume H(2) provides Desulfovibrio strains the capacity to participate as either partner in interspecies H(2) transfer. Interestingly the mechanisms of energy conversion, pathways of electron flow and the parameters determining the pathways used remain to be elucidated. Recent application of molecular genetic tools for the exploration of the metabolism of Desulfovibrio vulgaris Hildenborough has provided several new datasets that might provide insights and constraints to the electron flow pathways. These datasets include (1) gene expression changes measured in microarrays for cells cultured with different electron donors and acceptors, (2) relative mRNA abundances for cells growing exponentially in defined medium with lactate as carbon source and electron donor plus sulfate as terminal electron acceptor, and (3) a random transposon mutant library selected on medium containing lactate plus sulfate supplemented with yeast extract. Studies of directed mutations eliminating apparent key components, the quinone-interacting membrane-bound oxidoreductase (Qmo) complex, the Type 1 tetraheme cytochrome c(3) (Tp1-c(3)), or the Type 1 cytochrome c(3):menaquinone oxidoreductase (Qrc) complex, suggest a greater flexibility in electron flow than previously considered. The new datasets revealed the absence of random transposons in the genes encoding an enzyme with homology to Coo membrane-bound hydrogenase. From this result, we infer that Coo hydrogenase plays an important role in D. vulgaris growth on lactate plus sulfate. These observations along with those reported previously have been combined in a model showing dual pathways of electrons from the oxidation of both lactate and pyruvate during sulfate respiration. Continuing genetic and biochemical analyses of key genes in Desulfovibrio strains will allow further clarification of a general model for sulfate respiration.

SUBMITTER: Keller KL

PROVIDER: S-EPMC3129016 | biostudies-literature | 2011

REPOSITORIES: biostudies-literature

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Genetics and molecular biology of the electron flow for sulfate respiration in desulfovibrio.

Keller Kimberly L KL Wall Judy D JD

Frontiers in microbiology 20110629

Progress in the genetic manipulation of the Desulfovibrio strains has provided an opportunity to explore electron flow pathways during sulfate respiration. Most bacteria in this genus couple the oxidation of organic acids or ethanol with the reduction of sulfate, sulfite, or thiosulfate. Both fermentation of pyruvate in the absence of an alternative terminal electron acceptor, disproportionation of fumarate and growth on H(2) with CO(2) during sulfate reduction are exhibited by some strains. The ...[more]

PMID: 21747813

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Project description:In order to obtain a global view of energy metabolism pathways of the sulfate-reducer Desulfovibrio vulgaris Hildenborough and the proteins involved therein whole-genome microarrays were used to compare the transcriptional response of cells grown with hydrogen/sulfate, pyruvate/sulfate, lactate/thiosulfate, and pyruvate with limiting sulfate, relative to growth in standard lactate/sulfate condition. Growth with hydrogen/sulfate showed the largest number of differently expressed genes and the largest changes in expression levels. The most up-regulated energy metabolism genes were those coding for the periplasmic [NiFeSe] hydrogenase, followed by the Ech hydrogenase, and the most down-regulated were genes coding for the Coo hydrogenase. The results point to the involvement of formate cycling and the ethanol pathway during growth on hydrogen, whereas there is evidence for CO cycling during growth on lactate and pyruvate, but not on H2. Growth with thiosulfate showed the hallmarks of a reduced energy status of the cells with down regulation of the ATP synthase and the Qmo and Dsr complexes., whereas growth with pyruvate showed the smallest differences but an increased role for the Ech hydrogenase.that in this case functions in reverse from the case of growth with H2. The multiple periplasmic hydrogenases and formate dehydrogenases, do not display the same regulation pattern showing that their metabolic roles are not totally interchangeable. This result together with the observation that several genes coding for proteins that have not been biochemically characterised were considerably affected in this study, reveals a more complex energy metabolism than previously considered and provides guidance for further studies. Keywords: Growth protocol Desulfovibrio vulgaris Hildenborough was cultured at 37°C with thiosulfate as the only electron acceptor (with lactate as the electron donor) to mid-log phase. Cultures were also cultivated similarly using sulfate as the sole electron acceptor to mid-log phase. Gene expression profiles of cultures grown with thiosulfate as the electron acceptor were compared with those of the cultures grown with sulfate as the electron acceptor for dissimilatory sulfate reductiontion. Total RNA was harvested from four replicate cultures for microarray analysis. RNA extraction, purification, and labeling were performed independently on each cell sample. Two samples of each total RNA preparation were labeled, one with Cy3-dUTP and another with Cy5-dUTP for microarray hybridization (dye swap).

Dataset Information

Genetics and molecular biology of the electron flow for sulfate respiration in desulfovibrio.

Publications

Genetics and molecular biology of the electron flow for sulfate respiration in desulfovibrio.

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