title: Evidence against a direct antimicrobial role of H2O2 in the infection of plants by Erwinia chrysanthemi.
abstract: We have investigated the role of bacterial resistance to oxidative stress in pathogenesis. The oxyR gene from the pathogenic bacterium Erwinia chrysanthemi has been characterized. It is closely related to that found in Escherichia coli (88% overall amino acid identity). An E. chrysanthemi oxyR mutant strain was constructed by marker exchange. After induction with a sublethal dose of H2O2, this mutant was more sensitive to H2O2 and showed reduced levels of catalase and glutathione reductase activities, compared with the wild type. The oxyR mutant was unable to form individual colonies on agar plates unless catalase was added exogenously. However, it retained full virulence in potato tubers and tobacco leaves. These results suggest that the host-produced H2O2 has no direct antimicrobial effect on the interaction of E. chrysanthemi with the two plant species.
authors.affiliation: Departamento de Biotecnología-Universidad Politécnica de Madrid, E.T.S. Ingenieros Agrónomos, Ciudad Universitaria, Spain.
authors.forename: E
authors.initials: E
authors.lastname: Miguel
authors.forename: C
authors.initials: C
authors.lastname: Poza-Carrión
authors.forename: E
authors.initials: E
authors.lastname: López-Solanilla
authors.forename: I
authors.initials: I
authors.lastname: Aguilar
authors.forename: A
authors.initials: A
authors.lastname: Llama-Palacios
authors.forename: F
authors.initials: F
authors.lastname: García-Olmedo
authors.forename: P
authors.initials: P
authors.lastname: Rodríguez-Palenzuela
mesh_terms: D000595:Amino Acid Sequence; D002374:Catalase / Q000096:biosynthesis / Q000378:metabolism; D003001:Cloning, Molecular; D004268:DNA-Binding Proteins; D016974:Dickeya chrysanthemi / Q000201:enzymology / Q000235:genetics* / Q000472:pathogenicity; D005980:Glutathione Reductase / Q000096:biosynthesis / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010935:Plant Diseases / Q000382:microbiology*; D010947:Plants, Toxic; D012097:Repressor Proteins / Q000235:genetics* / Q000378:metabolism; D016415:Sequence Alignment; D014026:Nicotiana / Q000382:microbiology; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D012097:Repressor Proteins; D014157:Transcription Factors; D006861:Hydrogen Peroxide; D002374:Catalase; D005980:Glutathione Reductase