ISOLATION AND PHYSIOLOGICAL CHARACTERIZATION OF SYNTROPHUS-BUSWELLII STRAIN GA FROM A SYNTROPHIC BENZOATE DEGRADING STRICTLY ANAEROBIC COCULTURE

A stable, syntrophic benzoate-degrading bacterial consortium was enric hed from sewage sludge. It oxidized benzoate or 3-phenylpropionate to acetate, H-2 and CO2. As hydrogen scavengers Methanospirillum hungatei and Desulfovibrio sp. were present. The benzoate-degrading bacteria o f this syntrophic culture and of Syntrophus buswellii were able to gro w with benzoate/crotonate or crotonate alone in the absence of a hydro gen-utilizing partner organism. If crotonate was the only substrate, a cetate and butyrate were produced, while during growth on benzoate or 3-phenylpropionate crotonate served as a reducible co-substrate and wa s exclusively converted to butyrate. In the presence of crotonate inte rspecies hydrogen transfer was not necessary as a hydrogen sink. The b enzoate degrader was isolated as a pure culture with crotonate as the only carbon source. The pure culture could also grow with benzoate/cro tonate or 3-phenylpropionate/crotonate. The effect of high concentrati ons of crotonate and of acetate or butyrate on growth of the benzoate degrader was investigated. The benzoate degrader was compared with S. buswellii for its morphology, physiology and DNA base composition. Exc ept for the fact that S. buswellii was also able to grow on cinnamate, no differences between the two organisms were detected. The isolate i s named S. buswellii, strain GA.