title: Expression of genes for sulfur oxidation in the intracellular  chemoautotrophic symbiont of the deep-sea bivalve  Calyptogena okutanii.
abstract: To understand sulfur oxidation in thioauto-trophic deep-sea clam symbionts, we analyzed the recently reported genomes of two chemoautotrophic symbionts of Calyptogena okutanii (Candidatus Vesicomyosocius okutanii strain HA: Vok) and C. magnifica (Candidatus Ruthia magnifica strain Cm: Rma), and examined the sulfur oxidation gene expressions in the Vok by RT-PCR. Both symbionts have genes for sulfide-quinone oxidoreductase (sqr), dissimilatory sulfite reductase (dsr), reversible dissimilatory sulfite reductase (rdsr), sulfur-oxidizing multienzyme system (sox)(soxXYZA and soxB but lacking soxCD), adenosine phosphosulfate reductase (apr), and ATP sulfurylase (sat). While these genomes share 29 orthologous genes for sulfur oxidation implying that both symbionts possess the same sulfur oxidation pathway, Rma has a rhodanese-related sulfurtransferase putative gene (Rmag0316) that has no corresponding ortholog in Vok, and Vok has one unique dsrR (COSY0782). We propose that Calyptogena symbionts oxidize sulfide and thiosulfate, and that sulfur oxidation proceeds as follows. Sulfide is oxidized to sulfite by rdsr. Sulfite is oxidized to sulfate by apr and sat. Thiosulfate is oxidized to zero-valence sulfur by sox, which is then reduced to sulfide by dsr. In addition, thiosulfate may also be oxidized into sulfate by another component of sox. The result of the RT-PCR showed that genes (dsrA, dsrB, dsrC, aprA, aprB, sat, soxB, and sqr) encoding key enzymes catalyzing sulfur oxidation were all equally expressed in the Vok under three different environmental conditions (aerobic, semioxic, and aerobic under high pressure at 9 MPa), indicating that all sulfur oxidation pathways function simultaneously to support intracellular symbiotic life.
authors.affiliation: Marine Biodiversity Research Program, Institute of Biogeosciences, Japan Agency for Marine-Earth Science and Technology(JAMSTEC), Yokosuka 237-0061, Japan.
authors.forename: Maiko
authors.initials: M
authors.lastname: Harada
authors.forename: Takao
authors.initials: T
authors.lastname: Yoshida
authors.forename: Hirokazu
authors.initials: H
authors.lastname: Kuwahara
authors.forename: Shigeru
authors.initials: S
authors.lastname: Shimamura
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Takaki
authors.forename: Chiaki
authors.initials: C
authors.lastname: Kato
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Miwa
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Miyake
authors.forename: Tadashi
authors.initials: T
authors.lastname: Maruyama
mesh_terms: D000332:Aerobiosis; D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D049872:Bivalvia / Q000382:microbiology*; D052837:Chemoautotrophic Growth / Q000235:genetics*; D004790:Enzyme Induction; D020563:Gammaproteobacteria / Q000201:enzymology / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D005880:Gills / Q000382:microbiology; D006862:Hydrogen Sulfide / Q000378:metabolism; D050885:Hydrogensulfite Reductase / Q000096:biosynthesis / Q000235:genetics; D008386:Marine Biology; D053858:Metabolic Networks and Pathways / Q000235:genetics; D010084:Oxidation-Reduction; D010088:Oxidoreductases / Q000096:biosynthesis / Q000235:genetics; D011312:Pressure; D011808:Quinone Reductases / Q000096:biosynthesis / Q000235:genetics; D013430:Sulfate Adenylyltransferase / Q000096:biosynthesis / Q000235:genetics; D013431:Sulfates / Q000378:metabolism; D013455:Sulfur / Q000378:metabolism*; D013559:Symbiosis / Q000235:genetics*; D013884:Thiosulfate Sulfurtransferase / Q000096:biosynthesis / Q000235:genetics; D050862:Oxidoreductases Acting on Sulfur Group Donors
chemical_list: D001426:Bacterial Proteins; D006862:Hydrogen Sulfide; D050885:Hydrogensulfite Reductase; D010088:Oxidoreductases; D011808:Quinone Reductases; D013430:Sulfate Adenylyltransferase; D013431:Sulfates; D013455:Sulfur; D013884:Thiosulfate Sulfurtransferase; D050862:Oxidoreductases Acting on Sulfur Group Donors; C073412:sulfide quinone reductase