Bile salt biotransformations by human intestinal bacteria.

Degradation of steroids in the human gut.

The present invention relates to pharmaceutical compositions suitable for the treatment of chronic diseases associated with the presence of abnormal or an abnormal distribution of microflora in the gastrointestinal tract of a mammalian host, which compositions comprise viable non-pathogenic or attenuated pathogenic Clostridia. The compositions further comprise one or more additional viable non-pathogenic or attenuated pathogenic microorganisms selected from the group consisting of Bacteroides, Eubacteria, Fusobacteria, Propionibacteria, Lactobacilli, anaerobic cocci, Ruminococcus, E. coli, Gemmiger, Desulfomonas, Peptostreptococcus, and fungi. The present invention also provides pharmaceutical compositions suitable for the treatment of the same chronic diseases comprising viable non-pathogenic or attenuated pathogenic Escherichia coli, at least one strain of viable non-pathogenic or attenuated pathogenic Bacteroides and at least one strain of viable non-pathogenic or attenuated pathogenic microorganism.

Probiotic recolonisation therapy

Current trends in microbial steroid biotransformation.

Secondary bile acid-producing bacteria were isolated from human feces to improve our appreciation of the functional diversity and redundancy of the intestinal microbiota. In total, 619 bacterial colonies were isolated using a nutrient-poor agar medium and the level of secondary bile acid formation was examined in each by a liquid culture, followed by thin-layer chromatography. Of five strains analyzed by 16S rRNA gene sequencing and biochemical testing, one was identified as Bacteroides intestinalis AM-1, which was not previously recognized as a secondary bile-acid producer. GC-MS revealed that B. intestinalis AM-1 converts cholic acid (CA) and chenodeoxycholic acid into their 7-oxo derivatives, 7-oxo-deoxycholic acid (7-oxo-DCA) and 7-oxo-lithocholic acid, respectively. Thus, B. intestinalis AM-1 possesses 7alpha-hydroxysteroid dehydrogenase (7alpha-HSDH) activity. In liquid culture, B. intestinalis AM-1 showed a relatively higher productivity of 7-oxo-DCA than Escherichia coli HB101 and Bacteroides fragilis JCM11019(T), which are known to possess 7alpha-HSDH activity. The level of 7alpha-HSDH activity was higher in B. intestinalis AM-1 than in the other two strains under the conditions tested. The 7alpha-HSDH activity in each of the three strains is not induced by CA; instead, it is regulated in a growth phase-dependent manner.

Conversion of cholic acid and chenodeoxycholic acid into their 7-oxo derivatives by Bacteroides intestinalis AM-1 isolated from human feces.

NAD- and NADP-dependent 7alpha-hydroxysteroid dehydrogenases from bacteroides fragilis.

Formation of urso- and ursodeoxy-cholic acids from primary bile acids by a Clostridium limosum soil isolate.

We described two convenient assay methods to estimate bile acid deconjugation and bile acid bioconversion at the 7alpha-OH position by individual microorganisms grown in media containing taurocholic acid. The methods are based on (i) a selective chemical assay for taurine conjugates previously described and (ii) the use of a cell-free preparation of 7alpha-hydroxysteroid dehydrogenase from Escherichia coli to directly quantify 7alpha-OH groups. These non-chromatographic approaches have been applied to the study of three model strains of intestinal organisms, E. coli, Bacteroides fragilis, and Clostridium perfringens, grown in standard media in the presence of purified tritiated taurocholate. Assay results were confirmed by thin-layer chromatography solvent systems designed to separate conjugated from unconjugated bile acid and unmodified cholic acid nucleus from 7alpha-OH bioconversion product(s) (primarily 3alpha, 12alpha dihydroxy, 7-keto-cholanoic acid). In addition, 7alpha-hydroxysteroid dehydrogenase activity was demonstrated in cell-free extracts of all three organisms. Of the three organisms, only C. perfringens was demonstrated to (i) deconjugate taurocholic acid, (ii) contain 3alpha-hydroxysteroid dehydrogenase activity, (iii) convert cholic acid into at least five labeled metabolites visible on thin-layer chromatography, and (iv) catalyze significant tritium exchange with water in the medium.

Convenient Non-Chromatographic Assays for the Microbial Deconjugation and 7α-OH Bioconversion of Taurocholate

Lyophilized 7 alpha-hydroxysteroid dehydrogenase: a stable enzyme preparation for routine bile acid analysis.

Lyophilized Clostridium perfringens 3α- and Clostridium bifermentans 7α-hydroxysteroid dehydrogenases: two new stable enzyme preparations for routine bile acid analysis

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