title: Genetic and physiological characterization of ohr, encoding a protein involved in organic hydroperoxide resistance in Pseudomonas aeruginosa.
abstract: The ohr (organic hydroperoxide resistance) gene product of Pseudomonas aeruginosa was essential for optimal resistance to organic hydroperoxides (OHPs) but not to hydrogen peroxide or paraquat. A Deltaohr mutant was hypersusceptible to OHPs in disk inhibition assays and showed enhanced killing by OHPs in liquid culture. The ohr gene product was demonstrated to contribute to the decomposition of OHPs. Transcription of ohr was induced up to 15-fold upon exposure to OHPs, and this induction was independent of OxyR. Somewhat enhanced ohr-lacZ activity was detected in mutant strains affected in ohr, ahpC, and oxyR, and this phenotype correlated with hypersusceptibility to OHPs, suggesting overlapping or compensatory functions of the ohr and ahpC gene products. A single transcriptional start site for ohr was determined, and ohr transcripts were abundant in cells treated with a sublethal dose of OHPs but not in cells treated with paraquat. An 84-bp portion upstream of the ohr mRNA start site was sufficient for ohr induction by OHPs. Thus, the ohr gene appears to encode an antioxidant enzyme that is not part of the OxyR regulon yet is specifically induced by OHPs.
authors.affiliation: Department of Microbiology, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA. urs.ochsner@UCHSC.edu
authors.forename: U A
authors.initials: UA
authors.lastname: Ochsner
authors.forename: D J
authors.initials: DJ
authors.lastname: Hassett
authors.forename: M L
authors.initials: ML
authors.lastname: Vasil
mesh_terms: D001426:Bacterial Proteins / Q000502:physiology*; D001483:Base Sequence; D001555:Benzene Derivatives / Q000494:pharmacology; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D004352:Drug Resistance, Microbial; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D010544:Peroxidases / Q000235:genetics; D010545:Peroxides / Q000494:pharmacology*; D054464:Peroxiredoxins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011550:Pseudomonas aeruginosa / Q000187:drug effects*; D012097:Repressor Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics; D020122:tert-Butylhydroperoxide / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D001555:Benzene Derivatives; D004268:DNA-Binding Proteins; D010545:Peroxides; D012097:Repressor Proteins; D014157:Transcription Factors; C112257:organic hydroperoxide resistance protein, Xanthomonas campestris; D020122:tert-Butylhydroperoxide; D010544:Peroxidases; D054464:Peroxiredoxins; C007164:cumene hydroperoxide