Oxidation of sulfur and inorganic sulfur compounds in Acidianus ambivalens

Mechanisms of archaeal sulfur and inorganic sulfur compound oxidation were almost exclusively studied in Acidianus species, extremely thermophilic and acidophilic (pH(opt) 2-3), coccoid microorganisms living in acidic volcanic environments (solfataras) worldwide. They utilize H-2, H2S, S-0, polythionates, and metal sulfides as the most important sources of metabolic energy for CO, fixation during aerobic growth. The sulfur oxidation pathways include a soluble sulfur oxygenase reductase (SOR), membrane-bound thiosulfate and sulfite oxidoreductases, a soluble tetrathionate hydrolase, and an oxidative adenosine 5'-phosphosulfate reductase pathway. Here, the current knowledge of the biochemistry of these enzymes is discussed with a special focus on the implications of the recently published 3D structure of the SOR.