Figure 6
The sulfur oxidation model in A. thiooxidans based on documented models [[2],[6],[9]-[11]] , bioinformatics analysis of draft genome sequence. Abbreviations: SDO, sulfur dioxygenase; SQR, sulfide quinone reductase; TQO, thiosulfate:quinone oxidoreductase; TetH, tetrathionate hydrolase; Sox, sulfur oxidizing protein; HDR, heterodisulfide reductase; SOR, sulfur oxygenase reductase; TST, thiosulfate sulfurtransferase; A, phosphoadenosine phosphosulfate reductase; B, adenylylsulfate kinase. As is shown, the sulfur oxidation metabolism in A. thiooxidans A01 contains various sulfur oxidation systems and the electron transfer pathways in different cellular compartments. (i) In the outer membrane, elemental sulfur (S8) in the form of stable octasulfane ring is activated and transported into the periplasm as thiol-bound sulfane sulfur atoms (R-S-SnH); (ii) In the periplasm, R-S-SnH is oxidized by SDO, while tetrathionate is utilized by TetH to produce thiosulfate, and the thiosulfate is sequentially catalyzed by Sox complex; (iii) In the cytoplasmic membrane, SQR and TQO carry out their respective functions with electrons further transferred to terminal oxidase or NADH complex I; and (iv) In the cytoplasm, the particular enzymes perform the catalytic reaction by a sequence of steps that eventually produce sulfate.