THE DARK ANAEROBIC METABOLISM OF ACETONE AND ACETATE BY THE PHOTOSYNThETIC BACTERIUM RHODOPSEUDOMONAS

Previous studies have shown that the metabolism of acetone and acetate by the photosynthetic bacterium, Rhodopseudomonas gelatinosa, requires either light or oxygen as a source of energy (1, 2). The studies also showed that the cleavage of acetoacetate to acetat.e did not require an external source of energy. These observations are consistent with the known thermodynamic properties of the reactions which indicate that the cleavage of acetoacetate is an exergonic reaction. In view of current concepts of acetoacetate metabolism (3), it seemed possible that some of the energy liberated by this reaction could be utilized to satisfy part of the energy requirements for the metabolism of acetone and acetate. The coupling of acetone and acetate metabolism with acetoacetate decomposition, anaerobically in the dark, was investigated by means of C14-labeled acetone and acetate. The results indicate that the hydrolysis of acetoacetate can serve as a source of energy for these reactions. The coupling between acetoacetate decomposition and acetate metabolism was much more efficient than the coupling with acetone metabolism.