Sulfur Oxidation in Prokaryotes


In nature, sulfur occurs in many different oxidation states and is one of the most versatile elements in life. Reduced inorganic sulfur compounds serve either as sources for sulfur assimilation and incorporation into organic compounds or as the basis for oxidative energy‐related processes. Sulfur‐based energy transformation with concomitant mass transformations occurs almost exclusively among prokaryotes (Archaea and Bacteria). Dissimilatory sulfur oxidation in Eukarya is mediated by lithotrophic bacterial endosymbionts. Oxidation of reduced inorganic sulfur species by bacteria is a vital part of the global sulfur cycle and has applied importance in agriculture, waste treatment, biocorrosion and biomining. This article focuses on oxidation of reduced inorganic sulfur compounds and discusses the sulfur‐oxidizing reactions of selected phototrophic and chemotrophic prokaryotes.

Keywords: sulfur oxidation; phototrophic sulfur bacteria; chemotrophic sulfur bacteria

Figure 1.

Model of thiosulfate oxidation to sulfate by the Sox enzyme system of P. pantotrophus. The capital letters indicate the Sox proteins according to their genome designation. Y, Z, sulfur‐binding protein SoxYZ; X, A, haem enzyme complex SoxXA; B, sulfate thiohydrolase SoxB; C, D, heterotetrameric sulfane dehydrogenase Sox(CD)2.

Figure 2.

Overview of proposed pathways of thiotrophic sulfur transformations in phototrophic sulfur bacteria. Probably no single organism has all the reactions shown here. In the periplasm, the polysulfur chains are probably very short (n probably around 3 or 4), whereas the polysulfur chains in the sulfur globules can be very long (n>3 and possibly up to n>105 as for polymeric sulfur) (Dahl and Prange, ). Transport into the periplasm of sulfite formed by cytoplasmic Dsr proteins and oxidation of sulfite to sulfate in the periplasm as previously suggested (Dahl and Prange, ) cannot be completely excluded. PSRLC, polysulfide reductase like protein; R, organic residue possibly glutathione or glutathione amide; CycA, cytochrome c. Reproduced from Frigaard and Dahl , with permission from Elsevier.

Figure 3.

Hypothetical model of S0 oxidation in Ac. ambivalens with enzymes, enzyme locations, activities and possible nonenzymic reactions (not stoichiometric). Abbreviations and symbols: SOR, sulfur oxygenase reductase; SAOR, sulfite:acceptor oxidoreductase; SQR, sulfide quinone oxidoreductase; TQO, thiosulfate:quinone oxidoreductase; CQ, caldariella quinone; TTH, tetrathionate hydrolase; bc1‐anal.C., bc1‐analogous complex; Q‐Oxid., quinole oxidase; straight arrows, enzyme reactions; dotted arrows, nonenzymic reactions.



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Further Reading

Dahl C (2008) Inorganic sulfur compounds as electron donors in purple sulfur bacteria. In: Hell R, Dahl C, Knaff DB and Leustek T (eds) Sulfur in Phototrophic Organisms, pp. 289–317. Dordrecht: Springer.

Kletzin A (2008) Oxidation of sulfur and inorganic sulfur compounds in Acidianus ambivalens. In: Dahl C and Friedrich CG (eds) Microbial Sulfur Metabolism, pp. 184–201. Berlin, Heidelberg: Springer.

Markert S, Arndt C, Felbeck H et al. (2007) Physiological proteomics of the uncultured endosymbiont of Riftia pachyptila. Science 315: 247–250.

Rawlings DE (2005) Characteristics and adaptability of iron‐ and sulfur‐oxidizing microorganisms used for the recovery of metals from minerals and their concentrates. Microbial Cell Factories 4 doi:10.1186/1475‐2859‐4‐13.

Rother D, Ringk J and Friedrich CG (2008) Sulfur oxidation of Paracoccus pantotrophus: the sulfur‐binding protein SoxYZ is the target of the periplasmic thiol‐disulfide oxidoreductase SoxS. Microbiology 154: 1980–1988.

Sauvé V, Bruno S, Berks BC et al. (2007) The SoxYZ complex carries sulfur cycle intermediates on a peptide swinging arm. Journal of Biological Chemistry 282: 23194–23204.

Sievert SM, Hügler M, Taylor CD et al. (2008) Sulfur oxidation at deep sea hydrothermal vents. In: Dahl C and Friedrich CG (eds) Microbial Sulfur Metabolism, pp. 238–258. Berlin, Heidelberg: Springer.

Sorokin DY (2008) Diversity of halophilic sulfur‐oxidizing bacteria in hypersaline habitats. In: Dahl C and Friedrich CG (eds) Microbial Sulfur Metabolism, pp. 225–237. Berlin, Heidelberg: Springer.

Valenzuela L, Chi A, Beard S et al. (2008) Differential‐expression proteomics for the study of sulfur metabolism in the chemolithoautotrophic Acidothiobacillus ferrooxidans. In: Dahl C and Friedrich CG (eds) Microbial Sulfur Metabolism, pp. 77–86. Berlin, Heidelberg: Springer.

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Dahl, Christiane, Friedrich, Cornelius, and Kletzin, Arnulf(Dec 2008) Sulfur Oxidation in Prokaryotes. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1002/9780470015902.a0021155]