Project description:Desulfotomaculum reducens strain MI-1 is a Gram-positive, sulfate-reducing bacterium also capable of reducing Fe(III). Metal reduction in Gram-positive bacteria is poorly understood. Here, we investigated Fe(III) reduction with lactate, a non-fermentable substrate, as the electron donor. Lactate consumption is concomitant to Fe(III) reduction, but does not support significant growth, suggesting that little energy can be conserved from this process and that it may occur fortuitously. D. reducens can reduce both soluble (Fe(III)-citrate) and insoluble (hydrous ferric oxide, HFO) Fe(III). Because physically inaccessible HFO was not reduced, we concluded that reduction requires direct contact under these experimental conditions. This implies the presence of a surface exposed reductase capable of transferring electrons from the cell to the extracellular electron acceptor. With the goal of identifying candidate Fe(III) reductases, we carried out an investigation of the surface proteome (surfaceome) of D. reducens. Cell surface exposed proteins were extracted by trypsin cell shaving or by lysozyme treatment, and analyzed by liquid chromatography-tandem mass spectrometry.
Project description:Desulfotomaculum reducens is the first Gram-positive sulfate- and metal- reducing bacterium for which the transcriptomic response to uranium exposure has been evaluated. The genes upregulated during fermentative growth in the presence of U(VI) as compared to its absence included those encoding for proteins involved in respiration such as NADH quinone oxidoreductase and heterodisulfide reductase. This finding suggested that electrons were shuttled to the electron transport chain during fermentation which points to the reduction of U(VI) as a metabolic process. While U(IV) is typically insoluble and readily removable by filtration, U(IV) produced during active growth was not retained by a 0.2 µm pore size filter and filtration was not sufficient to differentiate between U(VI) and U(IV). In addition, genes involved in iron homeostasis were upregulated in the presence of uranium, which was consistent with the upregulation of genes involved in c-type cytochrome biogenesis. Despite the upregulation of cytochrome biosynthesis genes, the sole c-type cytochrome encoded in the genome was not differentially expressed. Finally, genes encoding metal efflux pumps were also upregulated indicating the toxic nature of uranium. Analysis of the time-dependent gene expression showed that sporulation was the dominant process at the early stationary phase and that the presence of U at that stage did not impact expression.
Project description:Desulfotomaculum acetoxidans Widdel and Pfennig 1977 was one of the first sulfate-reducing bacteria known to grow with acetate as sole energy and carbon source. It is able to oxidize substrates completely to carbon dioxide with sulfate as the electron acceptor, which is reduced to hydrogen sulfide. All available data about this species are based on strain 5575(T), isolated from piggery waste in Germany. Here we describe the features of this organism, together with the complete genome sequence and annotation. This is the first completed genome sequence of a Desulfotomaculum species with validly published name. The 4,545,624 bp long single replicon genome with its 4370 protein-coding and 100 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project.
Project description:Desulfotomaculum reducens is the first Gram-positive sulfate- and metal- reducing bacterium for which the transcriptomic response to uranium exposure has been evaluated. The genes upregulated during fermentative growth in the presence of U(VI) as compared to its absence included those encoding for proteins involved in respiration such as NADH quinone oxidoreductase and heterodisulfide reductase. This finding suggested that electrons were shuttled to the electron transport chain during fermentation which points to the reduction of U(VI) as a metabolic process. While U(IV) is typically insoluble and readily removable by filtration, U(IV) produced during active growth was not retained by a 0.2 µm pore size filter and filtration was not sufficient to differentiate between U(VI) and U(IV). In addition, genes involved in iron homeostasis were upregulated in the presence of uranium, which was consistent with the upregulation of genes involved in c-type cytochrome biogenesis. Despite the upregulation of cytochrome biosynthesis genes, the sole c-type cytochrome encoded in the genome was not differentially expressed. Finally, genes encoding metal efflux pumps were also upregulated indicating the toxic nature of uranium. Analysis of the time-dependent gene expression showed that sporulation was the dominant process at the early stationary phase and that the presence of U at that stage did not impact expression. This data set is a time course comparing sulfate and uranium reduction with fermentative growth.
Project description:The aim of this study was to unravel the methanol metabolism of Desulfotomaculum kuznetsovii. Anaerobic methylotrophs, such as methanogens and acetogens, use a pathway initiated by a cobalamine-containing methanol methyltransferase, whereas aerobic methylotrophs generally oxidize methanol to formaldehyde through a pathway initiated by a methanol dehydrogenase. Sulfate-respiring cells grown with methanol in the presence and absence of cobalt and vitamin B12 were analyzed and compared with cells grown with lactate or ethanol. Proteome analysis showed the presence of two methanol degrading pathways in D. kuznetsovii: a cobalt-dependent methanol methyltransferase and a cobalt-independent alcohol dehydrogenase. This is the first time that two methanol pathways have been shown to be present in a single microorganism, and we hypothesize this can give D. kuznetsovii a competitive advantage.