Dehydrogenation of Conjugated Cholic Acid by Escherichia coli

7α-Dehydrogenation of taurocholic acid and glycocholic acid by Escherichia coli (E. coli) was examined in aerobic and anaerobic culture conditions. Bile acids in the culture medium of E. coli were extracted, separated into free, glycine-conjugate and taurine-conjugate fractions by piperidinohydroxypropyl dextran gel column chromatography, hydrolyzed in alkali and analyzed by gas-liquid chromatography. Both conjugated cholic acids were dehydrogenated to the corresponding 3α,12α-dihydroxy-7-oxo-5β-cholan oic acid without deconjugation and no deconjugation of both conjugated cholic acid was detected in aerobic cultures. But there was little transformation in anaerobic cultures. These data suggest that conjugated cholic acids are taken up by E. coli in an aerobic culture as conjugate forms, dehydrogenated without deconjugation and excreted from the cell as conjugate forms.