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Deconjugation of Bile Salts by Bacteroides and Clostridium
Author(s) -
Masuda Noriyuki
Publication year - 1981
Publication title -
microbiology and immunology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.664
H-Index - 70
eISSN - 1348-0421
pISSN - 0385-5600
DOI - 10.1111/j.1348-0421.1981.tb00001.x
Subject(s) - bacteroides fragilis , taurine , bacteroides , clostridium perfringens , clostridium , biochemistry , microbiology and biotechnology , biology , bile acid , bacteria , chemistry , amino acid , genetics , antibiotics
Deconjugation of bile salts by four strains of Bacteroides and four strains of Clostridium was studied by use of resting cells and cell‐free culture supernatants. Bacteroides strains yielded active cells but showed relatively low bile salt hydrolase (BSH) activity in the culture supernatants while the reverse was the case for the spore‐forming clostridial strains. BSH was formed constitutively and was oxygen insensitive. The optimum pH was between 4.5 and 5.0. Marked substrate specificity was found in two strains, one Clostridium and one Bacteroides , which showed restricted activity against taurine conjugates. Bacteroides in general attacked the taurine conjugates of di‐hydroxy bile acids more readily than the trihydroxy taurine conjugates. Deconjugated bile acid moieties were further modified by some resting cells, depending on the bacterial strain while no enzymatic activity other than that of BSH was found in the culture supernatants. Cells of B. fragilis 2536 performed 7 α ‐dehydrogenation when the pH of the medium allowed the reaction, and this oxidative process was markedly enhanced in the presence of an abundant supply of oxygen as a terminal electron acceptor. C. perfringens PB 6K produced the 3‐keto product in addition to the 3 β ‐hydroxy derivative of the liberated bile acids and the formation of the latter derivative seemed to take place without preliminary deconjugation.