An anaerobic bacterium, strain DP7, was isolated from human feces in mineral medium with formate and 0.02"east extract as energy and carbon source. This rod-shaped motile bacterium used pyruvate, lactate, formate, hydrogen, butyrate, and ethanol as electron donor for sulfite reduction. Other electron acceptors such as thiosulfate, nitrate and fumarate stimulated growth in the presence of 0.02"east extract and formate. Acetate was the only product during fermentative growth on pyruvate. Six mol of pyruvate were fermented to 7 mol of acetate. 13C-NMR labeling experiments showed homoacetogenic 13C-CO2 incorporation into acetate. The pH and temperature optimum of fermentative growth on pyruvate was 7.4 and 37 °C, respectively. The growth rate under these conditions was approximately 0.10 h-1. Strain DP7 was identified as a new strain of Desulfitobacterium frappieri on the basis of 16S rRNA sequence analysis (99 imilarity) and DNA-DNA hybridization (reassociation value of 83€with Desulfitobacterium frappieri TCE1. In contrast to described Desulfitobacterium strains, the newly isolated strain has not been isolated from a polluted environment and did not use chloroethenes or chlorophenols as electron acceptor.