The enzymic formation of hydrogen sulphide by certain heterotrophic bacteria

Abstract

With washed cells of Proteus vulgaris and Serratia marces-cens, under anaerobic conditions, formation of H2S from organic S compounds was very specific, inasmuch as compounds possessing the a amino [beta] thiol carboxylic acid structure (cysteine), or its -S-S- form, yielded over 75% of their S as H2S. Substituted cysteine compounds and a thiol carboxylic acids, when attacked, yielded only very small amounts of H2S; other organic S compounds yielded none. It is concluded that formation of H2S from organic S compounds depends on the presence of a specific enzyme in the bacterial cell; it was found in cells of certain aerobes and facultative anaerobes, and in 1 strict anaerobe. Addition of cysteine to the medium employed for preparing the bacterial cells apparently stimulates formation of the enzyme. The mechanisms of forming H2S from cysteine and from thiosulphate are apparently distinct.