title: Tellurite effects on Rhodobacter capsulatus cell viability and superoxide dismutase activity under oxidative stress conditions.
abstract: Cells of the facultative photosynthetic bacterium Rhodobacter capsulatus (MT1131 strain) incubated with 10 microg ml-1 of the toxic oxyanion tellurite (TeO2-(3)) exhibited an increase in superoxide dismutase activity. The latter effect was also seen upon incubation with sublethal amounts of paraquat, a cytosolic generator of superoxide anions (O2-), in parallel with a strong increase in tellurite resistance (TeR). A mutant strain (CW10) deficient in SenC, a protein with similarities to peroxiredoxin/thiol:disulfide oxidoreductases and a homologue of mitochondrial Sco proteins, was constructed by interposon mutagenesis via the gene transfer agent system. Notably, the absence of SenC affected R. capsulatus resistance to periplasmic O2- generated by xanthine/xanthine oxidase but not to cytosolic O2- produced by paraquat. Further, the absence of SenC did not affect R. capsulatus tellurite resistance. We conclude that: (1) cytosolic-generated O2- enhances TeR of this bacterial species; (2) small amounts of tellurite increase SOD activity so as to mimic the early cell response to oxidative stress; (3) SenC protein is required in protection of R. capsulatus against periplasmic oxidative stress; and finally, (4) SenC protein is not involved in TeR, possibly because tellurite does not generate O-2 at the periplasmic space level.
authors.affiliation: Department of Biology, Microbiology Unit, University of Bologna, 40126 Bologna, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Borsetti
authors.forename: Valentina
authors.initials: V
authors.lastname: Tremaroli
authors.forename: Francesca
authors.initials: F
authors.lastname: Michelacci
authors.forename: Roberto
authors.initials: R
authors.lastname: Borghese
authors.forename: Christine
authors.initials: C
authors.lastname: Winterstein
authors.forename: Fevzi
authors.initials: F
authors.lastname: Daldal
authors.forename: Davide
authors.initials: D
authors.lastname: Zannoni
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000502:physiology; D015169:Colony Count, Microbial; D024881:Drug Resistance, Bacterial / Q000235:genetics; D017353:Gene Deletion; D016254:Mutagenesis, Insertional; D018384:Oxidative Stress; D010269:Paraquat / Q000633:toxicity; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics / Q000502:physiology; D016354:Rhodobacter capsulatus / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D013482:Superoxide Dismutase / Q000378:metabolism*; D013691:Tellurium / Q000633:toxicity*
chemical_list: D001426:Bacterial Proteins; D045322:Photosynthetic Reaction Center Complex Proteins; C096879:SenC protein, Rhodobacter capsulatus; D013482:Superoxide Dismutase; C026660:tellurous acid; D013691:Tellurium; D010269:Paraquat