Supporting information for Eisen et al. (2002) Proc. Natl. Acad. Sci. USA, 10.1073/pnas.132181499.
Supporting Figure 8Fig. 8. Sulfur metabolism and evolution in C. tepidum. (A) Model for sulfur metabolism in C. tepidum. Thiosulfate oxidation in the periplasm is proposed to occur by a modification of the SoxZY-, SoxXA-, and SoxB-dependent scheme proposed by Friedrich et al. (1). Because SoxC and SoxD are missing in C. tepidum, it is proposed that the sulfane sulfur of thiosulfate is transferred to the polysulfide pool as shown. External sulfide is oxidized to disulfide by sulfide quinone oxidoreductase. Polysulfide reductase could serve to activate polysulfide reductively for further oxidation, although the mechanism by which sulfide enters the cytoplasm is unknown. Oxidation of sulfide to sulfate in the cytoplasm would occur through the actions of dissimilatory siroheme sulfite reductase (DsrABC, etc.), adenosine-5'-phosphosulfate reductase (APS reductase), and ATP sulfurylase. Aspects of this model include ideas derived from Pott and Dahl (2) and C. Dahl (personal communication). (B) Evolution of sulfite reductase DsrAB proteins. Note recent duplications in C. tepidum. Homologs of the DsrAB were identified with FASTA3 and BLASTP searches of GenBank and low-redundancy protein database at TIGR. Alignments and trees were generated as described (3). Numbers indicate bootstrap values. That the species relationships on the two branches are identical indicates the duplication occurred before the speciation events for these lineages.
1. Friedrich, C. G., Rother, D., Bardischewsky, F., Quentmeier, A. & Fischer, J. (2001) Appl. Environ. Microbiol. 67, 2873–2882.
2. Pott, A. S. & Dahl, C. (1998) Microbiology 144, 1881–1894.
3. Salzberg, S. L., White, O., Peterson, J. & Eisen, J. A. (2001) Science 292, 1903–1906.
