Anaerobic respiration with elemental sulfur and with disulfides

Anaerobic respiration with elemental sulfur/polysulfide or organic disulfid es is performed by several bacteria and archaea, but has only been investig ated in a few organisms in detail. The electron transport chain that cataly zes polysulfide reduction in the Gram-negative bacterium Wolinella succinog enes consists of a dehydrogenase (formate dehydrogenase or hydrogenase) and polysulfide reductase. The enzymes are integrated in the cytoplasmic membr ane with the catalytic subunits exposed to the periplasm. The mechanism of electron transfer from formate dehydrogenase or hydrogenase to polysulfide reductase is discussed. The catalytic subunit of polysulfide reductase belo ngs to the family of molybdopterin-dinucleotide-containing oxidoreductases. From the hyperthermophilic archaeon Pyrodictium abyssi isolate TAG11 an in tegral membrane complex has been isolated which catalyzes the reduction of sulfur with H-2 as electron donor. This enzyme complex; which is composed o f a hydrogenase and a sulfur reductase, contains heme groups and several ir on-sulfur clusters, but does not contain molybdenum or tungsten. In methano genic archaea, the heterodisulfide of coenzyme M and coenzyme B is the term inal electron acceptor of the respiratory chain. In methanogens belonging t o the order Methanosarcinales, this respiratory chain is composed of a dehy drogenase, the membrane-soluble electron carrier methanophenazine, and hete rodisulfide reductase. The catalytic subunit of heterodisulfide reductase c ontains only iron-sulfur clusters. An iron-sulfur cluster may directly be i nvolved in the reduction of the disulfide substrate. (C) 1999 Published by Elsevier Science B.V. All rights reserved.