Unsaturated Organic Acids as Terminal Electron Acceptors for Reductase Chains of Anaerobic Bacteria

This paper summarizes the current knowledge of unsaturated organic acids in their role as terminal electron acceptors for reductase chains of anaerobic bacteria. The mechanisms and enzyme systems involved in the reduction of fumarate by Escherichia coli, Wolinella succinogenes, and some species of the genus Shewanella are considered. Particular attention is given to reduction of the double bond of the unnatural compound methacrylate by the δ-proteobacterium Geobacter sulfurreducens AM-1. Soluble periplasmic flavocytochromes c, found in bacteria of the genera Shewanella and Geobacter, are involved in the hydrogenation of fumarate (in Shewanella species) and methacrylate (in G. sulfurreducens AM-1). In E. coli and W. succinogenes, fumarate is reduced in cytosol by membrane-bound fumarate reductases. The prospects for research into organic acid reduction at double bonds in bacteria are discussed.