Abstract
The 7 alpha-dehydroxylation of chenodeoxycholic acid (CDCA) and cholic acid (CA) by a Eubacterium lentum-like intestinal anaerobe was specifically enhanced by the bacteroides present in mixed cultures and also by the addition to the growth medium of cell extracts from the bacteroides. The 7 alpha-dehydroxylating organism also possessed 7 alpha-hydroxysteroid dehydrogenase activity, and, in collaboration with a 7 beta-dehydrogenating organism, converted ursodeoxycholic acid (UDCA) into CDCA. Large quantities of lithocholic acids were produced from UDCA as well as CDCA in in vitro cocultures of these three kinds of microorganisms.
Highlights
The 7a-dehydroxylation of chenodeoxycholicacid (CDCA)and cholic acid (CA) by a Eubacterium lentum-like intestinal anaerobe was enhanced by the bacteroides present in mixed cultures and by the addition to the growth medium of cell extracts from the bacteroides
Strain c-25 showed both 7a-dehydroxylase and 7a-hydroxysteoid dehydrogenase activities,but only a small portion of CDCAwas converted into LCA or a 7-keto acid
In a previous study [12], we reported on the interconversion between UDCA (7B-OH) and chenodeoxycholic acid (CDCA) (7aOH) by the combined action of two kinds of microorganismasctive for 7a- and 7B-hydroxysteroid dehydrogenase, respectively
Summary
The basal medium was the same 2% peptone-1 % yeast extract broth buffered at pH 7.5 (2% PY) as used previously for the detection of microbial 7a-dehydroxylation of bile acids [11]. After addition of bile acid at a final concentration of 150 pg/ml, the medium was dispensed in 4-mlquantities in smalltest tubes, andused immediatelyafter preparation andautoclaving. The test strains, singly or in combination, were grown in this medium for 2-8 days in an anaerobic jar under an atmosphere of 90% N2 and 10% C 0 2 (oxygen-free),and the spent culture medium was assayed for bile acid metabolites. Bacterial growth was measured by reading the percentransmittance of light at 660 nm on a photometer (%T)and the pH of the culture was checked electrometrically to insure that it was maintained at analkaline pH value (7adehydroxylation can barely take place in an acidic environment) (1 1)
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