Project description:Green sulfur bacteria are in the family Chlorobiaceae, which is composed of four distinct genera, namely, Chlorobaculum, Chlorobium, Prosthecochloris, and Chloroherpeton, with Chlorobium species being the most commonly represented in genome studies. We have now sequenced only the fourth species of Chlorobaculum, which established Chlorobaculum sp. 24CR as a separate species and should help characterize the genus.
Project description:Chlorobaculum tepidum is an anaerobic green sulfur bacterium which oxidizes sulfide, elemental sulfur, and thiosulfate for photosynthetic growth. It can also oxidize sulfide to produce extracellular S0 globules, which can be further oxidized to sulfate and used as an electron donor. Here we performed label free quantitative proteomics on total cell lysates prepared from different metabolic states, including a sulfur production state (10 hours post incubation, PI), the beginning of sulfur consumption (20 hours PI) and the end of sulfur consumption (40 hours PI), respectively. We observed an increased abundance of the sulfide:quinone oxidoreductase Sqr proteins in 20PI indicated a sulfur production state. The periplasmic thiosulfate-oxidizing Sox enzymes and the dissimilatory sulfite reductase Dsr subunits showed an increased abundance in 20PI, corresponding to the sulfur-consuming state. In addition, we found that the abundance of the heterodisulfide-reductase and the sulfhydrogenase operons was influenced of electron donor availability and may be associated with sulfur metabolism. Further, we isolated and analyzed the extracellular sulfur globules in the different metabolic states in order to study their morphology and the sulfur cluster composition, yielding 58 previously uncharacterized proteins in purified globules. Our results show that Cba tepidum regulates the cellular levels of enzymes involved in sulfur metabolism in response to the availability of reduced sulfur compounds.
Project description:The green sulfur bacterium Chlorobaculum tepidum is proposed to oxidize sulfide and elemental sulfur via sulfite as an obligate intermediate. The sulfite pool is predicted to be contained in the cytoplasm and be oxidized by the concerted action of ApsBA, which directly oxidizes sulfite, and QmoABC, which transfers electrons from ApsBA to the quinone pool. Like other green sulfur bacteria, C. tepidum was unable to use exogenously provided sulfite as the sole electron donor. However, exogenous sulfite significantly stimulated the growth yield of sulfide limited batch cultures. The growth of C. tepidum mutant strains, CT0867/qmoB::TnOGm and CT0868/qmoC::TnOGm, was not increased by sulfite. Furthermore, these strains accumulated sulfite and displayed a growth yield decrease when grown on sulfide as the sole electron donor. These results support an obligate, cytoplasmic sulfite intermediate as part of the canonical sulfur oxidation pathway in C. tepidum that requires the Qmo complex for oxidation.
Project description:We report here the complete genome sequences of four atrazine-degrading bacteria. Their genomes will serve as references for determining the genetic changes that have occurred during an evolution experiment.
