The nuclear dehydrogenation of steroids by intestinal bacteria.

We have postulated that bacteria able to dehydrogenate the bile-acid nucleus are important in the aetiology of cancer of the colon. In this paper we report on screening for the ability to carry out two such reactions. The relevant enzymes are produced by a high proportion of strains of Clostridium paraputrificum, C. tertium and C. indolis, and by small numbers of strains in other clostridial species, but not by organisms of the other genera tested. Strains able to dehydrogenate the bile-acid nucleus represent a high proportion of the lecithinase-negative clostridia isolated from faeces of people living in Britain but a low proportion of those from people living in Uganda or Hong Kong.