title: [Antioxidative function of katG gene in Rhizobium leguminosarum].
abstract: OBJECTIVE
  Catalase-peroxidase KatG can protect bacteria from damage of reactive oxygen species. This study investigated the antioxidative function of catalase - peroxidase gene katG in Rhizobium leguminosarum 3841.
  
  
  METHODS
  katG mutant strain of R. leguminosarum was constructed by homologous recombination. The wild type, katG mutant and complementary strain were challenged by oxidative stress and symbiotic ability.
  
  
  RESULTS
  Under free - living conditions, the katG mutant exhibited no generation time extension. However, cells of the katG strain were deficient in consumption oj high concentrations of H2O2and were vulnerable after aquick exposure to H2O2. The real-time qRT-PCR results showec that katG was expressed independently of exogenous H2O2. In contrast, the katG mutant strain displayed higher expres, level of ohrB gene and lower expression level of grxC than the wild type. With regard to symbiotic capacities with Pisum sativum, the katG mutant was indistinguishable in root nodule nitrogenase activity and competition nodule ability from the wild type. However, katG gene was expressed significantly lower in bacteroids than that in free-living strains. Besides, the colonization of the pea rhizosphere by the katG mutant was impaired compared to that of the wild type.
  
  
  CONCLUSIONS
  ThE deletion of katG had nosignificant effect in 3841 under the free-living and symbiosis condition but was essential ir antioxidation and colonization of the pea rhizosphere. Although katG could not be induced by H2O2, it still played acentra role in antioxidation and symbiotic nitrogen fixation by regulating the antioxidant genes such as ohrB and grxC.
authors.forename: Yanlin
authors.initials: Y
authors.lastname: Zhou
authors.forename: Donglan
authors.initials: D
authors.lastname: He
authors.forename: Xiaohua
authors.initials: X
authors.lastname: Li
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Zeng
authors.forename: Mengyang
authors.initials: M
authors.lastname: Tian
authors.forename: Guojun
authors.initials: G
authors.lastname: Cheng
mesh_terms: D000975:Antioxidants / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002374:Catalase / Q000235:genetics / Q000378:metabolism*; D006861:Hydrogen Peroxide / Q000378:metabolism; D009586:Nitrogen Fixation; D018532:Pisum sativum / Q000382:microbiology / Q000502:physiology; D016961:Rhizobium leguminosarum / Q000201:enzymology* / Q000235:genetics / Q000502:physiology; D053204:Root Nodules, Plant / Q000382:microbiology / Q000502:physiology; D013559:Symbiosis
chemical_list: D000975:Antioxidants; D001426:Bacterial Proteins; D006861:Hydrogen Peroxide; D002374:Catalase