[The significance of the bacterial steroid degradation for the etiology of large bowel cancer. VI. Degradation of deoxycholic acid by saccharolytic bacteroides-species (author's transl)].

When testing 36 laboratory strains of the strictly anaerobic Bacteroides species B. vulgatus, B. fragilis, B. thetaiotaomicron, and B. distasonis, we found activities for degradation of cholate (3alpha, 7alpha, 12alpha-trihydroxy-5 beta-cholanoate) (1) and chenodeoxycholate (3alpha, 7alpha-dihydroxy-5 beta-cholanoate) (2) widely, but not universally distributed in these bacteria. The same strains were also tested for their metabolic activities in regard to deoxycholate (3alpha, 12alpha-dihydroxy-5 beta-cholanoate). These tests were performed with anaerobically growing cultures and with resting cells, incubated aerobically, in media of defined composition indicated in the foregoing papers. After precultivation in a medium containing bile and deoxycholate 22 of 35 strains (63 per cent), growing anaerobically, and 28 of 36 aerobically incubated tests (78 per cent) transformed deoxycholate. In summa the number of active strains was 30 of 36 (83 per cent). All active strains, produced one metabolite only, all metabolities had the same chromatographic properties as shown by analytical thin-layer chromatography in two solvent systems. However, it has still to be decided whether only one degradation product is formed from deoxycholate, corresponding to the transformation of chenodeoxycholate (2), since the chromatographic properties of the metabolites permit the formation of 3alpha-hydroxy-12-oxo- and/or 3-oxo-12alpha-hydroxy-cholanoate. Structural evidence, however, could hitherto not be demonstrated. The enzymatic activity, responsible for the metabolism, has to be induced, it is not identical with the activity oxidizing the 7alpha-hydroxyl group. No further details concerning enzyme induction and activity regulation have as yet been discovered. The side chain of deoxycholate can not be degraded by Bacteroides species, neither by anaerobically growing cultures nor by aerobically incubated resting cells.