Dissimilatory sulphate reduction with acetate as electron donor

Abstract

Acetate oxidation by sulphate was studied with Desulfobacter postgatei . Cell extracts of the organism were found to contain high activities of the following enzymes: citrate synthase, aconitase, isocitrate dehydrogenase, a-ketoglutarate dehydrogenase, succinate dehydrogenase, fumarase, malate dehydrogenase and pyruvate synthase. It is concluded that acetate oxidation with sulphate in D. postgatei proceeds via the citric acid cycle with the synthesis of pyruvate from acetyl CoA and CO ₂ as an anaplerotic reaction. The apparent K _s for acetate oxidation by D. postgatei as determined in vivo was near 0.2 mM. The apparent Ks for acetate fermentation to methane and CO ₂ by Methanosarcina barkeri was 3 mM. The significantly lower K _s for acetate of the sulphate reducer explains why methane formation from acetate in natural habitats is apparently inhibited by sulphate.