Project description:Gemmatimonas phototrophica is the only phototrophic member of the recently discovered bacterial phylum Gemmatimonadetes. It was isolated from a freshwater lake in the Gobi desert and first described in 2014. So far, Gemmatimonas phototrophica is the only bacterium to have received a complete set of photosynthesis-related genes by horizontal gene transfer from an ancient phototrophic species from the phylum Proteobacteria. This organism illustrates the possibility for engineering phototrophic capability in a non-phototrophic organism and is therefore of great interest to the field of synthetic biology. The structure of the photosynthetic reaction center-light harvesting 1 complex is under investigation by cryo-EM. Proteomic analysis verified the identities of the expected protein components of this complex and, additionally revealed polypeptides that were previously undiscovered and could be mapped to the cryo-EM images.
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.