title: Role of the dpr product in oxygen tolerance in Streptococcus mutans.
abstract: We have previously identified and characterized the alkyl hydroperoxide reductase of Streptococcus mutans, which consists of two components, Nox-1 and AhpC. Deletion of both nox-1 and ahpC had no effect on the sensitivity of S. mutans to cumene hydroperoxide or H(2)O(2), implying that the existence of another antioxidant system(s) independent of the Nox-1-AhpC system compensates for the deficiency. Here, a new antioxidant gene (dpr for Dps-like peroxide resistance gene) was isolated from the S. mutans chromosome by its ability to complement an ahpCF deletion mutant of Escherichia coli with a tert-butyl hydroperoxide-hypersensitive phenotype. The dpr gene complemented the defect in peroxidase activity caused by the deletion of nox-1 and ahpC in S. mutans. Under aerobic conditions, the dpr disruption mutant carrying a spectinomycin resistance gene (dpr::Spc(r) mutant) grew as well as wild-type S. mutans in liquid medium. However, the dpr::Spc(r) mutant could not form colonies on an agar plate under air. In addition, neither the dpr::Spc(r) ahpC::Em(r)::nox-1 triple mutant nor the dpr::Spc(r) sod::Em(r) double mutant was able to grow aerobically in liquid medium. The 20-kDa dpr gene product Dpr is an iron-binding protein. Synthesis of Dpr was induced by exposure of S. mutans cells to air. We propose a mechanism by which Dpr confers aerotolerance on S. mutans.
authors.affiliation: Laboratory of Applied Microbiology, Department of Molecular and Cell Biology, Graduate School of Agricultural Science, Tohoku University, Amamiya-machi, Aoba-ku, Sendai 981-8555, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Yamamoto
authors.forename: M
authors.initials: M
authors.lastname: Higuchi
authors.forename: L B
authors.initials: LB
authors.lastname: Poole
authors.forename: Y
authors.initials: Y
authors.lastname: Kamio
mesh_terms: D000332:Aerobiosis; D000596:Amino Acids / Q000032:analysis; D000975:Antioxidants / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001483:Base Sequence; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D003470:Culture Media; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D004352:Drug Resistance, Microbial; D005293:Ferritins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D033862:Iron-Binding Proteins; D008969:Molecular Sequence Data; D016296:Mutagenesis; D010100:Oxygen; D013295:Streptococcus mutans / Q000187:drug effects* / Q000235:genetics / Q000254:growth & development; D033863:Transferrin-Binding Proteins
chemical_list: D000596:Amino Acids; D000975:Antioxidants; D001426:Bacterial Proteins; D002352:Carrier Proteins; D003470:Culture Media; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; C083911:DPS protein, Bacteria; D033862:Iron-Binding Proteins; D033863:Transferrin-Binding Proteins; D005293:Ferritins; D006861:Hydrogen Peroxide; D010100:Oxygen