ABSTRACT
Until about 1970, it was generally believed that anaerobic nonphotosynthetic bacteria could synthesize ATP only by substrate level phosphorylation reactions and that the occurrence of electron transport phosphorylation was restricted to aerobic bacteria. In the meantime, it has been discovered that strictly anaerobic bacteria can derive the ATP required for growth from the reduction of fumarate, with either succinate or propionate as the end product. An acceptor with similar properties is not at the disposal of anaerobic bacteria under most conditions. Most of the known anaerobic bacteria synthesize their hydrogen acceptors from the growth substrates. Pyruvate is a well-known example of a hydrogen acceptor which is reduced to lactate during the fermentation of glucose by many bacteria. The CoA-esters of acrylate and crotonate are well-known hydrogen acceptors in anaerobic bacteria that form fatty acids as end products.
