Human feces contain: 1) Chemotrophic anaerobic bacteria (strains XII, 57, IV) identified with D. desulfuricans ssp. faecalis (nov. ssp.) at a level approaching 10 7/g. 2) Organotrophic anaerobic gram positive rods (strains 30, 35, and 43) at between 10(5) and 10 7/g. 3) Chemo-organotrophic anaerobic gram positive rods (strains 22, 27, 47, and 66) were present at 40 5/g. Strains of these two last groups have not been described in the literature and are not found in any accepted toxonomic scheme.