title: CorA affects tolerance of Escherichia coli and Salmonella enterica serovar Typhimurium to the lactoperoxidase enzyme system but not to other forms of oxidative stress.
abstract: The enzyme lactoperoxidase is part of the innate immune system in vertebrates and owes its antimicrobial activity to the formation of oxidative reaction products from various substrates. In a previous study, we have reported that, with thiocyanate as a substrate, the lactoperoxidase system elicits a distinct stress response in Escherichia coli MG1655. This response is different from but partly overlapping with the stress responses to hydrogen peroxide and to superoxide. In the current work, we constructed knockouts in 10 lactoperoxidase system-inducible genes to investigate their role in the tolerance of E. coli MG1655 to this antimicrobial system. Five mutations resulted in a slightly increased sensitivity, but one mutation (corA) caused hypersensitivity to the lactoperoxidase system. This hypersensitive phenotype was specific to the lactoperoxidase system, since neither the sensitivity to hydrogen peroxide nor to the superoxide generator plumbagin was affected in the corA mutant. Salmonella enterica serovar Typhimurium corA had a similar phenotype. Although corA encodes an Mg2+ transporter and at least three other inducible open reading frames belonged to the Mg2+ regulon, repression of the Mg stimulon by Mg2+ did not change the lactoperoxidase sensitivity of either the wild-type or corA mutant. Prior exposure to 0.3 mM Ni2+, which is also transported by CorA, strongly sensitized MG1655 but not the corA mutant to the lactoperoxidase system. Furthermore, this Ni2+-dependent sensitization was suppressed by the CorA-specific inhibitor Co(III) hexaammine. These results indicate that CorA affects the lactoperoxidase sensitivity of E. coli by modulating the cytoplasmic concentrations of transition metals that enhance the toxicity of the lactoperoxidase system.
authors.affiliation: Katholieke Universiteit Leuven, Laboratory of Food Microbiology, Kasteelpark Arenberg 22, B-3001 Leuven, Belgium.
authors.forename: Jan
authors.initials: J
authors.lastname: Sermon
authors.forename: Eva M-R P
authors.initials: EM
authors.lastname: Wevers
authors.forename: Leentje
authors.initials: L
authors.lastname: Jansen
authors.forename: Philipp
authors.initials: P
authors.lastname: De Spiegeleer
authors.forename: Kristof
authors.initials: K
authors.lastname: Vanoirbeek
authors.forename: Abram
authors.initials: A
authors.lastname: Aertsen
authors.forename: Chris W
authors.initials: CW
authors.lastname: Michiels
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D003470:Culture Media; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005816:Genetic Complementation Test; D018869:Heat-Shock Response; D006861:Hydrogen Peroxide / Q000494:pharmacology; D007784:Lactoperoxidase / Q000378:metabolism*; D009154:Mutation; D009285:Naphthoquinones / Q000494:pharmacology; D018384:Oxidative Stress; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism / Q000502:physiology
chemical_list: D001426:Bacterial Proteins; D027682:Cation Transport Proteins; C072716:CorA protein, Salmonella; D003470:Culture Media; D029968:Escherichia coli Proteins; D009285:Naphthoquinones; D006861:Hydrogen Peroxide; D007784:Lactoperoxidase; C014758:plumbagin