Oxidant-inducible resistance to hydrogen peroxide killing in Agrobacterium tumefaciens requires the global peroxide sensor-regulator OxyR and KatA.
Induced adaptive and cross-protective responses to peroxide stress are important strategies used by bacteria to survive stressful environments. We have shown that exposure to low levels of peroxide (adaptive) and superoxide anions (cross-protection) induced high levels of resistance to peroxide killing in Agrobacterium tumefaciens. The mechanisms and genes involved in these processes have not been identified. Here, the roles played by peroxide (oxyR) and superoxide (soxR) global regulators and a catalase gene (katA) during these responses were investigated. H2O2-induced adaptive protection was completely abolished in both the oxyR and katA mutants. Superoxide generator (menadione)-induced cross-protection to H2O2 killing was observed in a soxR mutant, but not in either an oxyR or a katA mutant. In vivo analysis of the katA promoter, using a katA::lacZ transcriptional fusion, revealed that it could be induced by menadione in an oxyR-dependent manner. These results lead us to conclude that H2O2 and superoxide anions directly or indirectly oxidize OxyR and it is the resulting activation of katA expression that is responsible for the induced protection against lethal concentrations of H2O2.
Eiamphungporn
Warawan
W
Department of Biotechnology, Faculty of Science, Mahidol University, Bangkok 10400, Thailand.
Nakjarung
Kaewkanya
K
Prapagdee
Benjaphorn
B
Vattanaviboon
Paiboon
P
Mongkolsuk
Skorn
S
D000222:Adaptation, Physiological; D016960:Agrobacterium tumefaciens / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D002374:Catalase / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000235:genetics; D024881:Drug Resistance, Bacterial; D005798:Genes, Bacterial; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology*; D009154:Mutation; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress; D013481:Superoxides / Q000378:metabolism / Q000494:pharmacology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D024483:Vitamin K 3 / Q000494:pharmacology
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D016877:Oxidants; D014157:Transcription Factors; D013481:Superoxides; C070724:SoxR protein, Bacteria; D024483:Vitamin K 3; D006861:Hydrogen Peroxide; D002374:Catalase