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DesulfobacterRANK: GenusTAXONOMY: Bacteria -> Proteobacteria -> delta/epsilon subdivisions -> Deltaproteobacteria -> Desulfobacterales -> Desulfobacteraceae -> Desulfobacter OVERVIEW: Oval to rod-shaped or slightly curved to vibrio-shaped cells, 0.5–2.5 × 1.5–8 μm. Occur singly or in pairs. Spore formation is not observed. Gram negative. Cells are motile by single polar flagella or nonmotile, but motility can be lost during cultivation. Strict anaerobe with a respiratory type of metabolism. Chemoorganotrophs or chemoautotrophs. Acetate is the preferred general electron donor and carbon source, and is completely oxidized to CO2. Some species also use ethanol, and a few species use H2/CO2 or pyruvate. H2-utilizing Desulfobacter hydrogenophilus grows autotrophically with CO2 as the sole carbon source. Sulfate, and usually sulfite and thiosulfate, serve as terminal electron acceptors and are reduced to H2S. Sulfur and nitrate are not used as terminal electron acceptors. Fermentative growth has not been observed. Desulfoviridin is absent, but desulforubidin is present in some species. The major menaquinone is MK-7. Growth occurs in simple defined media containing sulfide as a reductant. Most species require vitamins. Many members of this genus can fix N2. The addition of ≥7 g NaCl and ≥1 g MgCl2·6H2O per liter medium is usually stimulatory or required for growth. The optimal temperature range for growth is 28–34°C. Thermophilic species have not been described. The optimal pH range for growth is 6.5–7.4. Carbon monoxide dehydrogenase activity is absent. Acetyl-CoA oxidation and CO2 fixation with H2 as electron donor in D. hydrogenophilus is accomplished via a modified TCA cycle. Desulfobacter species are most common in anoxic brackish or marine sediments, but some types may be found in anoxic freshwater sediments or in activated sludge. The mol% G + C of the DNA is: 45–49. Type species: Desulfobacter postgatei |