Pyruvate Metabolism in Sarcina maxima

Abstract

The mechanisms of pyruvate cleavage and hydrogen production by Sarcina maxima were studied. It was found that a phosphoroclastic system for pyruvate oxidation, similar to that occurring in saccharolytic clostridia, is present in S. maxima . Cleavage of pyruvate by extracts of the latter organism resulted in the formation of acetyl phosphate, CO 2 , and electrons which were transferred to ferredoxin. Formate was not an intermediate in this system. Pyruvate oxidation was coupled with ferredoxin-dependent nicotinamide adenine dinucleotide phosphate (NADP) reduction. A hydrogenase, active in particulate extracts of S. maxima , did not accept electrons from reduced ferredoxin. Formate was detected as a fermentation product when S. maxima was grown in media buffered with CaCO 3 . Whole cells and extracts degraded formate to H 2 and CO 2 . The evidence suggests that electrons generated by ferredoxin-linked pyruvate oxidation by S. maxima are not used for H 2 production, but that they serve for the reduction of NADP. Reduced NADP may be utilized by the organisms for synthesis of cell material. Production of H 2 by S. maxima may occur through a pyruvate clastic system similar to that present in coliform bacteria.