Bacterial Formation of Sulphide from oxidized Forms of inorganic Sulphur

5 sediments and 6 water samples from a former mining area have examined for the presence of sulphide-froorming bacteria. 6 strins of clostridia, 2 Citrobacter sp. and 7 strains of Alteromonas were isolated and tested for their ability to form suplphide from a variety of oxidized inorganic S-sources (tetrathionate, thiosulphate, sulphite) together with cysteine. The clostridia were able to do so readily from thiosulphate and sulpite. All of the orther strains were positive when tested in a complex medium supplemented with thiosulphate but were negative in a defined medium. All strains of Altemononas putrefaciens from the present investigation were able to reduce cysteine to sulphide at the expense of both glucose and sucrose. Attention is directed to certain unresolved aspects of microbial sulphur metabolism