SIGNIFICANCE OF BACTERIAL STEROID DEGRADATION FOR ETIOLOGY OF LARGE BOWEL CANCER .5. TRANSFORMATION OF CHENODEOXYCHOLIC ACID BY SACCHAROLYTIC BACTEROIDES-SPECIES

  • 1 January 1976
    • journal article
    • research article
    • Vol. 162  (5-6) , 506-518
Abstract
A total of 36 strains of the obligate anaerobic Bacteroides species B. vulgatus, B. fragilis, B. thetaiotaomicron and B. distasonis were analyzed to test their faculties to metabolize chenodeoxycholate. For experiments with growing cultures, a synthetic medium with inorganic salts, glucose, citrate, amino acids, vitamins and hemin was used. The same medium, but without amino acids and vitamins, was used for experiments with resting cells, incubated aerobically. After preincubation in a medium containing bile and deoxycholate, 26 strains of 35 (74%) could degrade this bile acid, when cultivated anaerobically, compared to 30 strains of 36 (83%), when incubated aerobically. There are 32 active strains (89%). With the exception of 2 strains, which formed 2 transformation products, all active strains formed 1 degradation product only. All strains but 1, active when cultured anaerobically, belong to the species B. fragilis and B. thetaiotaomicron. As can be seen by the results of aerobic incubation most strains of B. vulgatus possess the degradative activity, found inactive under anaerobic conditions. Its regulatory mechanism is different from the 2 other species. TLC, gas chromatography and combined gas chromatography-mass spectrometry were used for the identification of transformation products. These methods demonstrated the bacteria to metabolize chenodeoxycholate to 3.alpha.-hydroxy-7-oxo-5.beta.-cholanoate, growing anaerobically or incubated aerobically. The 2nd degradation products of 2 strains, found in traces or as by-products, could not be identified because of minor amounts.