Syntrophobacter pfennigii sp nov, new syntrophically propionate-oxidizing anaerobe growing in pure culture with propionate and sulfate

A new strain of syntrophically propionate-oxidizing fermenting bacteria, strain KoProp1, was isolated from anoxic sludge of a municipal sewage plant. It oxidized propionate or lactate in cooperation with the hydrogen- and formate-utilizing Methanospirillum hungatei and grew as well in pure culture without a syntrophic partner with propionate or lactate plus sulfate as energy source. In all cases, the substrates were oxidized stoichiometrically to acetate and CO2, with concomitant formation of methane or sulfide. Cells formed gas vesicles in the late growth phase and contained cytochromes b and c, a menaquinone-7, and desulforubidin, but no desulfoviridin. Enzyme measurements in cell-free extracts indicated that propionate was oxidized through the methylmalonyl CoA pathway. Protein pattern analysis by SDS-PAGE of cell-free extracts showed that strain KoProp1 differs significantly from Syntrophobacter wolinii and from the propionate-oxidizing sulfate reducer Desulfobulbus propionicus. 16S rRNA sequence analysis revealed a significant resemblance to S. wolinii allowing the assignment of strain KoProp1 to the genus Syntrophobacter as a new species, S. pfennigii.