ACTIVATION AND DEGRADATION OF BENZOATE, 3-PHENYLPROPIANATE AND CROTONATE BY SYNTROPHUS-BUSWELLII STRAIN GA - EVIDENCE FOR ELECTRON-TRANSPORT PHOSPHORYLATION DURING CROTONATE RESPIRATION

A strictly anaerobic, benzoate-degrading bacterium, Syntrophus buswell ii strain GA, was able to degrade benzoate or 3-phenylpropionate to ac etate, CO2 and H-2, if the hydrogen partial pressure was sufficiently low. The hydrogen was removed in syntrophic coculture by Methanospiril lum hungatei or by Desulfovibrio sp. through interspecies hydrogen tra nsfer or in pure culture by the use of crotonate as reducible cosubstr ate. Alternatively, S. buswellii strain GA could grow in pure culture with crotonate. Activities of seven catabolic enzymes were measured in crude cell extracts of S. buswellii strain GA grows with various subs trates and of crotonate-grown S. buswellii strain DSM 2612A. Benzoate, 3-phenylpropionate and crotonate were activated by CoA ligases. Gluta ryl-CoA dehydrogenase was found to be involved in the degradation of a romatic compounds and enzymes catalysing beta-oxidation were involved in the reaction sequence from crotonyl-CoA to acetate. A c-type cytoch rome was present in the cytoplasm, whereas b-type cytochromes were ass ociated with the membranes of both S. buswellii strains grown on croto nate. These indicated the presence of an electron-transport system. A high growth yield of crotonate-grown S. buswellii strain GA might be e xplained by electron-transport phosphorylation in addition to substrat e-level phosphorylation.