A strictly anaerobic, Gram-positive, motile and spore-forming bacterium, designated strain TYR6, was isolated from olive mill wastewaters on cinnamic acid. Cells were straight rods and occurred singly, in pairs or in short chains. Strain TYR6 utilized a number of carbohydrates (glucose, fructose, mannose, maltose, sorbitol, myo-inositol, and ribose) and peptides (yeast extract, Casamino acids, Biotrypcase, peptone, and gelatin), grew optimally at 37àand at pH 7, and had a G+C content of 29.1 mol%. Strain TYR6 was phylogenetically related to Clostridium bifermentans (similarity of 99%) with which it bears a high phenotypic similarity and DNA homology (80%). In addition, strain TYR6 shares withC. bifermentans ATCC 638Tand DSM 630 the ability to metabolize cinnamic acid (but not any of its derivatives), with or without glucose supplementation, via the reduction of the double bond of the C3-aliphatic side chain to 3-phenylpropionic (hydrocinnamic) acid. Addition of glucose accelerated the rate of growth and increased markedly the conversion yield of cinnamic acid to 3-phenylpropionic acid. Based on the results, we propose to emend the description of C. bifermentans.