title: Roles of reactive oxygen species-degrading enzymes of Francisella tularensis SCHU S4.
abstract: Francisella tularensis is a facultative intracellular bacterium utilizing macrophages as its primary intracellular habitat and is therefore highly capable of resisting the effects of reactive oxygen species (ROS), potent mediators of the bactericidal activity of macrophages. We investigated the roles of enzymes presumed to be important for protection against ROS. Four mutants of the highly virulent SCHU S4 strain with deletions of the genes encoding catalase (katG), glutathione peroxidase (gpx), a DyP-type peroxidase (FTT0086), or double deletion of FTT0086 and katG showed much increased susceptibility to hydrogen peroxide (H2O2) and slightly increased susceptibility to paraquat but not to peroxynitrite (ONOO(-)) and displayed intact intramacrophage replication. Nevertheless, mice infected with the double deletion mutant showed significantly longer survival than SCHU S4-infected mice. Unlike the aforementioned mutants, deletion of the gene coding for alkyl-hydroperoxide reductase subunit C (ahpC) generated a mutant much more susceptible to paraquat and ONOO(-) but not to H2O2. It showed intact replication in J774 cells but impaired replication in bone marrow-derived macrophages and in internal organs of mice. The live vaccine strain, LVS, is more susceptible than virulent strains to ROS-mediated killing and possesses a truncated form of FTT0086. Expression of the SCHU S4 FTT0086 gene rendered LVS more resistant to H2O2, which demonstrates that the SCHU S4 strain possesses additional detoxifying mechanisms. Collectively, the results demonstrate that SCHU S4 ROS-detoxifying enzymes have overlapping functions, and therefore, deletion of one or the other does not critically impair the intracellular replication or virulence, although AhpC appears to have a unique function.
authors: Department of Clinical Microbiology, Bacteriology, and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden.
authors: Johan
authors: J
authors: Binesse
authors: Department of Clinical Microbiology, Bacteriology, and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden.
authors: Helena
authors: H
authors: Lindgren
authors: Department of Clinical Microbiology, Bacteriology, and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden.
authors: Lena
authors: L
authors: Lindgren
authors: National Research Council Canada, Institute for Biological Sciences, Ottawa, Ontario, Canada.
authors: Wayne
authors: W
authors: Conlan
authors: Department of Clinical Microbiology, Bacteriology, and Laboratory for Molecular Infection Medicine Sweden (MIMS), Umeå University, Umeå, Sweden Anders.Sjostedt@umu.se.
authors: Anders
authors: A
authors: Sjöstedt
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D005260:Female; D005604:Francisella tularensis / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism / Q000472:pathogenicity; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D006540:Herbicides / Q000494:pharmacology; D006861:Hydrogen Peroxide / Q000494:pharmacology; D008264:Macrophages / Q000166:cytology / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D010269:Paraquat / Q000494:pharmacology; D017382:Reactive Oxygen Species / Q000378:metabolism*; D014774:Virulence
chemical_list: D006540:Herbicides; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D010269:Paraquat