Krebs (1937) reported that acetate and a number of other substrates were oxidized under anaerobic conditions by nonproliferating suspensions of Eschrichia coli when fumarate was added as an oxidant. These observations resulted from a study of the role of fumarate in respiration, and no consideration was given to the mechanism of acetate oxidation. The over-all reaction for the oxidation of acetate is illustrated in equation (1) .