Project description:Chemoautotrophic bacteria belonging to the genus Sulfurimonas in the class Campylobacteria (formerly classified as Epsilonproteobacteria) play a key role in the sulfur cycle in a variety of oxygen-deficient or –limited and sulfide-rich marine and terrestrial environments. Previously, they were identified as key players in the turnover of zero-valence sulfur, a central intermediate in the marine sulfur cycle, and S. denitrificans was further shown to be able to oxidize cyclooctasulfur. However, at present the mechanism involved in the activation and metabolism of cyclooctasulfur is not known. To this end, we assessed the transcriptome and proteome of S. denitrificans grown with either thiosulfate or cyclooctasulfur as the electron donor. While the overall profiles under the two growth conditions were rather similar, distinct differences were observed that could be attributed to the utilization of cyclooctasulfur. This included a higher abundance of expressed genes and proteins related to attachment in the presence of cyclooctasulfur and the differential expression of the sulfur-oxidation multienzyme complex (SOX). S. denitrificans uses the SOX system for the oxidation of reduced sulfur compounds, including two copies of the sulfur-binding SoxYZ proteins, encoded in two gene clusters: soxABXYZ1 and soxCDYZ2. While the proteins of both operons of the SOX system were detected in the presence of thiosulfate, only proteins of the soxCDYZ2 operon were detected when grown with cylcooctasulfur. Based on these findings a model for the oxidation of cylcooctasulfur is being proposed that might also apply to other Campylobacteria that share the same arrangement of the SOX system. Our results have implications for interpreting metatranscriptomic and -proteomic data and for the observed high level of diversification of soxYZ2 among sulfur-oxidizing Campylobacteria.
Project description:The purple sulfur bacterium Allochromatium vinosum DSM 180T is one of the best studied sulfur-oxidizing anoxygenic phototrophic bacteria and has been developed into a model organism for laboratory-based studies of oxidative sulfur metabolism. Here, we took advantage of the organism’s high metabolic versatility and performed whole-genome transcriptional profiling to investigate the response of A. vinosum cells upon exposure to sulfide, thiosulfate, elemental sulfur or sulfite as compared to photoorganoheterotrophic growth on malate. Differential expression (at least twofold) of 1149 genes was observed, corresponding to 30% of the A. vinosum genome. A total of 549 genes were identified for which relative transcription increased at least twofold during growth on one of the different sulfur sources while relative transcription of 599 genes decreased. A significant number of genes that were strongly induced have documented sulfur-metabolism-related functions. Among these are the dsr genes including dsrAB for dissimilatory sulfite reductase and the sgp genes for the proteins of the sulfur globule envelope thus confirming former results. In addition we were able to identify new genes encoding proteins with appropriate subcellular localization and properties to participate in oxidative dissimilatory sulfur metabolism. Two of these were chosen for inactivation and phenotypic analyses of the respective mutant strains. This approach verified the importance of the encoded proteins for the oxidation of sulfide and thereby also documented the suitability of comparative transcriptomics for the identification of new sulfur-related genes in anoxygenic phototrophic sulfur bacteria.
Project description:The purple sulfur bacterium Allochromatium vinosum DSM 180T is one of the best studied sulfur-oxidizing anoxygenic phototrophic bacteria and has been developed into a model organism for laboratory-based studies of oxidative sulfur metabolism. Here, we took advantage of the organism’s high metabolic versatility and performed whole-genome transcriptional profiling to investigate the response of A. vinosum cells upon exposure to sulfide, thiosulfate, elemental sulfur or sulfite as compared to photoorganoheterotrophic growth on malate. Differential expression (at least twofold) of 1149 genes was observed, corresponding to 30% of the A. vinosum genome. A total of 549 genes were identified for which relative transcription increased at least twofold during growth on one of the different sulfur sources while relative transcription of 599 genes decreased. A significant number of genes that were strongly induced have documented sulfur-metabolism-related functions. Among these are the dsr genes including dsrAB for dissimilatory sulfite reductase and the sgp genes for the proteins of the sulfur globule envelope thus confirming former results. In addition we were able to identify new genes encoding proteins with appropriate subcellular localization and properties to participate in oxidative dissimilatory sulfur metabolism. Two of these were chosen for inactivation and phenotypic analyses of the respective mutant strains. This approach verified the importance of the encoded proteins for the oxidation of sulfide and thereby also documented the suitability of comparative transcriptomics for the identification of new sulfur-related genes in anoxygenic phototrophic sulfur bacteria.
Project description:Sulfur-oxidizing epsilonproteobacteria are common in a variety of sulfidogenic environments. These autotrophic and mixotrophic sulfur-oxidizing bacteria are believed to contribute substantially to the oxidative portion of the global sulfur cycle. In order to better understand the ecology and roles of sulfur-oxidizing epsilonproteobacteria, in particular those of the widespread genus Sulfurimonas, in biogeochemical cycles, the genome of Sulfurimonas denitrificans DSM1251 was sequenced. This genome has many features, including a larger size (2.2 Mbp), that suggest a greater degree of metabolic versatility or responsiveness to the environment than seen for most of the other sequenced epsilonproteobacteria. A branched electron transport chain is apparent, with genes encoding complexes for the oxidation of hydrogen, reduced sulfur compounds, and formate and the reduction of nitrate and oxygen. Genes are present for a complete, autotrophic reductive citric acid cycle. Many genes are present that could facilitate growth in the spatially and temporally heterogeneous sediment habitat from where Sulfurimonas denitrificans was originally isolated. Many resistance-nodulation-development family transporter genes (10 total) are present; of these, several are predicted to encode heavy metal efflux transporters. An elaborate arsenal of sensory and regulatory protein-encoding genes is in place, as are genes necessary to prevent and respond to oxidative stress.
Project description:The purple sulfur bacterium Allochromatium vinosum DSM 180T is one of the best studied sulfur-oxidizing anoxygenic phototrophic bacteria and has been developed into a model organism for laboratory-based studies of oxidative sulfur metabolism. Here, we took advantage of the organismM-bM-^@M-^Ys high metabolic versatility and performed whole-genome transcriptional profiling to investigate the response of A. vinosum cells upon exposure to sulfide, thiosulfate, elemental sulfur or sulfite as compared to photoorganoheterotrophic growth on malate. Differential expression (at least twofold) of 1149 genes was observed, corresponding to 30% of the A. vinosum genome. A total of 549 genes were identified for which relative transcription increased at least twofold during growth on one of the different sulfur sources while relative transcription of 599 genes decreased. A significant number of genes that were strongly induced have documented sulfur-metabolism-related functions. Among these are the dsr genes including dsrAB for dissimilatory sulfite reductase and the sgp genes for the proteins of the sulfur globule envelope thus confirming former results. In addition we were able to identify new genes encoding proteins with appropriate subcellular localization and properties to participate in oxidative dissimilatory sulfur metabolism. Two of these were chosen for inactivation and phenotypic analyses of the respective mutant strains. This approach verified the importance of the encoded proteins for the oxidation of sulfide and thereby also documented the suitability of comparative transcriptomics for the identification of new sulfur-related genes in anoxygenic phototrophic sulfur bacteria. In this study, the relative genomic expression profiles of A. vinosum DSM 180T growing photolithoautotrophically on different reduced sulfur compounds were determined in comparison to those of cells grown photoorganoheterothrophically on malate (RCV medium) at exactly the same light intensity. The malate-containing medium was supplied with 0.815 mM sulfate in order to satisfy the sulfur-requirement for biosynthesis of sulfur-containing cell constituents. Three independent photolithoautotrophic cultures each, grown on sulfide, thiosulfate or sulfite were harvested 1 h, 2 h or 7 h, respectively, after inoculation. When elemental sulfur was the substrate, four independent cultures were harvested 3 h after inoculation.
Project description:The purple sulfur bacterium Allochromatium vinosum DSM 180T is one of the best studied sulfur-oxidizing anoxygenic phototrophic bacteria and has been developed into a model organism for laboratory-based studies of oxidative sulfur metabolism. Here, we took advantage of the organismM-bM-^@M-^Ys high metabolic versatility and performed whole-genome transcriptional profiling to investigate the response of A. vinosum cells upon exposure to sulfide, thiosulfate, elemental sulfur or sulfite as compared to photoorganoheterotrophic growth on malate. Differential expression (at least twofold) of 1149 genes was observed, corresponding to 30% of the A. vinosum genome. A total of 549 genes were identified for which relative transcription increased at least twofold during growth on one of the different sulfur sources while relative transcription of 599 genes decreased. A significant number of genes that were strongly induced have documented sulfur-metabolism-related functions. Among these are the dsr genes including dsrAB for dissimilatory sulfite reductase and the sgp genes for the proteins of the sulfur globule envelope thus confirming former results. In addition we were able to identify new genes encoding proteins with appropriate subcellular localization and properties to participate in oxidative dissimilatory sulfur metabolism. Two of these were chosen for inactivation and phenotypic analyses of the respective mutant strains. This approach verified the importance of the encoded proteins for the oxidation of sulfide and thereby also documented the suitability of comparative transcriptomics for the identification of new sulfur-related genes in anoxygenic phototrophic sulfur bacteria. In this study, the relative genomic expression profiles of A. vinosum DSM 180T growing photolithoautotrophically on different reduced sulfur compounds were determined in comparison to those of cells grown photoorganoheterothrophically on malate (RCV medium) at exactly the same light intensity. The malate-containing medium was supplied with 0.815 mM sulfate in order to satisfy the sulfur-requirement for biosynthesis of sulfur-containing cell constituents. Three independent photolithoautotrophic cultures each, grown on sulfide, thiosulfate or sulfite were harvested 1 h, 2 h or 7 h, respectively, after inoculation. When elemental sulfur was the substrate, four independent cultures were harvested 3 h after inoculation.
Project description:Sulfurimonas denitrificans was originally isolated from coastal marine sediments. It can grow with thiosulfate and nitrate or sulfide and oxygen. Recently sequencing of its genome revealed that it encodes periplasmic and cytoplasmic [NiFe]-hydrogenases but the role of hydrogen for its metabolism has remained unknown. We show the first experimental evidence that S. denitrificans can indeed express a functional hydrogen uptake active hydrogenase and can grow on hydrogen. In fact, under the provided conditions it grew faster and denser on hydrogen than on thiosulfate alone and even grew with hydrogen in the absence of reduced sulfur compounds. In our experiments, at the time points tested, the hydrogen uptake activity appeared to be related to the periplasmic hydrogenase and not to the cytoplasmic hydrogenase. Our data suggest that under the provided conditions S. denitrificans can grow more efficiently with hydrogen than with thiosulfate.