A strain (ToHP1) of anaerobic bacteria which degrades 3-hydroxypropanoate was isolated in pure culture from the sludge of an anaerobic digestor at a Tokyo sewage treatment facility. The strain grew by degrading 3-hydroxypropanoate, lactate, and pyruvate to propionate and acetate. It also grew auxotrophically by degrading 2-hydroxybutanoate to butyrate and propionate in the presence of acetate. Cells were lemon-shaped rods; 1.4 to 3.6 mu m in length and 0.5 to 1.1 mu m in width. Spores with a diameter of 0.8 to 1.1 mu m were formed subterminally. The strain occurred singly or in pairs. It stained gram-positive. The strain grew optimally at 30 to 35 degrees C and ca. pH 7.2. It required yeast extract for growth. The strain did not utilize nitrate, sulfate, sulfite, thiosulfate, or elemental sulfur as an electron acceptor. The guanine plus cytosine content of the DNA was 43 mol%. Strain ToHP1 was identified as a member of the genus Clostridium.