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DesulfobacteriumRANK: GenusTAXONOMY: Bacteria -> Proteobacteria -> delta/epsilon subdivisions -> Deltaproteobacteria -> Desulfobacterales -> Desulfobacteraceae -> Desulfobacterium OVERVIEW: Oval to rod-shaped, or spherical cells, 0.9–2 × 1.5–3 μm. Occur singly or in pairs; sometimes also in loose chains. Spore formation is not observed. Gram negative. Some species are motile, but motility may be lost during cultivation. Strict anaerobes with a respiratory and a fermentative type of metabolism. Chemoorganotrophs or chemoautotrophs, using formate, butyrate, higher fatty acids, other organic acids, alcohols, and H2 + CO2 as electron donors and as carbon sources; these compounds are completely oxidized to CO2. One species can use nicotinate as sole electron donor and carbon source. Growth on acetate and propionate is usually very slow. Sulfate and other oxidized sulfur compounds serve as terminal electron acceptors and are reduced to H2S. Sulfur and nitrate are not used as terminal electron acceptors. Some species may grow slowly in the absence of an external electron acceptor by fermentation of lactate, pyruvate, malate, and fumarate. Optimal growth temperature, 26–29°C. Anoxic media (with sulfide as a reductant) and vitamins are required for growth. Desulfobacterium species require brackish or marine concentrations of NaCl and MgCl2. Cells contain cytochromes of the b- and c-type. Carbon monoxide dehydrogenase activity is commonly observed, indicating the operation of the anaerobic C1 pathway (carbon monoxide dehydrogenase pathway, Wood pathway) for complete oxidation of acetyl-CoA, or for CO2 fixation during autotrophic growth. Desulfobacterium species are widespread in brackish or marine sediments, but occur less frequently in freshwater habitats. The mol% G + C of the DNA is: 45–48. Type species: Desulfobacterium autotrophicum |