DESULFUROMONAS-ACETOXIDANS GEN-NOV AND SP-NOV - NEW ANAEROBIC, SULFUR-REDUCING, ACETATE-OXIDIZING BACTERIUM

Anaerobic sea or fresh water media with acetate and elemental S yielded enrichments of a new type of strictly anaerobic, rod-shaped, laterally flagellated, gram-negative bacterium. Three pure culture-strains from different sulfide-containing sea water sources were characterized in detail and are described as a new genus and species DESULFUROMONAS acetoxidans. The new bacterium is unable to ferment organic substances; it obtains energy for growth by anaerobic S respiration. Acetate, ethanol or propanol can serve as C and energy source for growth; their oxidation to CO2 is stoichiometrically linked to the reduction of elemental S to sulfide. Organic disulfide compounds, malate or fumarate are the only other electron acceptors used. Butanol and pyruvate are used in the presence of malate only; no other organic compounds are utilized. Biotin is required as a growth factor. The following dry weight yields per mole of substrate are obtained: in the presence of S: 4.21 g on acetate, 9.77 g on ethanol; in the presence of malate: 16.5 g on acetate, 34.2 g on ethanol and 46.2 g on pyruvate. Accumulations of cells are pink; cell suspensions exhibit absorption spectra resembling those of c-type cytochromes (absolute maxima at 419, 523 and 553 nm). Malate-ethanol grown cells contain a b-type cytochrome in addition. In the presence of acetate, ethanol or propanol, Desulfuromonas strains form robust growing syntrophic mixed cultures with phototrophic green sulfur bacteria.