Enzymic sulphide oxidation by Thiobacillus concretivorus

Abstract

1. 1. The oxidation of sulphide by Thiobacillus concretivorus, Thiobacillus thiooxidans and Thiobacillus thioparus is an enzymic process associated with cell membranes. 2. 2. The first reaction is an oxidative one involving electron transfer through the cytochrome system to oxygen. It is inhibited by sodium diethyldithiocarbamate and Tris-HCl, but not by CO or sodium azide. 3. 3. The K m of sulphide oxidations is 2·10 −6 M. 4. 4. Conjugates sulphur compounds with distinctive spectral properties are subsequently fromed. These may be polysulphides. This step is inhibited by CO. 5. 5. A native cytochrome c which has been purified 120-fold from T. concretivorus is involved in the formation of the polysulphur intermediates. CO binds to this cytochrome, and inhibits the production of the polysulphur compounds which absorb around 320 mμ. 6. 6. A role for copper and the formation of a bound intermediate is proposed. 7. 7. A heat-stable factor, essential for sulphide oxidation, has been extracted in acetone from the membrane fraction.