Desulforhopalus vacuolatus gen nov, sp nov, a new moderately psychrophilic sulfate-reducing bacterium with gas vacuoles isolated from a temperate estuary

A new type of gas-vacuolated, sulfate-reducing bacterium was isolated at 10 degrees C from reduced mud (E(0) <0) obtained from a temperate estuary with Ifiiosulfate and lactate as substrates. The strain was moderately psychrophilic with optimum growth at 18-19 degrees C and a maximum growth temperature of 24 degrees C. Propionate, lactate, and alcohols served as electron donors and carbon sources. The organism grew heterotrophically only with hydrogen as electron donor. Propionate and lactate were incompletely oxidized to acetate; traces of lactate were fermented to propionate, CO2 and possibly acetate in the presence of sulfate. Pyruvate was utilized both with and without an electron acceptor present. The strain did not contain desulfoviridin. The G+C content was 48.4 mol%. The differences in the 16S rRNA sequence of the isolate compared with that of its closest phylogenetic neighbors, bacteria of the genus Desulfobulbus, support the assignment of the isolate to a new genus. The isolate is described as the type strain of the new species and genus, Desulforhopalus vacuolatus.