title: Lethal hydroxyl radical accumulation by a lactococcal bacteriocin, lacticin Q.
abstract: The antimicrobial mechanism of a lactococcal bacteriocin, lacticin Q, can be described by the toroidal pore model without any receptor. However, lacticin Q showed different degrees of activity (selective antimicrobial activity) against Gram-positive bacteria even among related species. The ability of lacticin Q to induce pore formation in liposomes composed of lipids from different indicator strains indicated that its selective antimicrobial activity could not be attributed only to membrane lipid composition. We investigated the accumulation of deleterious hydroxyl radicals after exposure to lacticin Q as a contributing factor to cell death in the indicator strains. When lacticin Q of the same concentration as the MIC or minimum bactericidal concentration was added to the indicator cultures, high levels of hydroxyl radical accumulation were detected. Treatment with hydroxyl radical scavengers, thiourea and 2,2'-bipyridyl, decreased the levels of hydroxyl radical accumulation and recovered cell viability. These results suggest that, with or without pore formation, the final antimicrobial mechanism of lacticin Q is the accumulation of hydroxyl radicals, which varies by strain, resulting in the selective antimicrobial activity of lacticin Q.
authors.affiliation: Laboratory of Microbial Technology, Division of Applied Molecular Microbiology and Biomass Chemistry, Department of Bioscience and Biotechnology, Faculty of Agriculture, Graduate School, Fukuoka, Japan.
authors.forename: Mengqi
authors.initials: M
authors.lastname: Li
authors.forename: Fuminori
authors.initials: F
authors.lastname: Yoneyama
authors.forename: Nayu
authors.initials: N
authors.lastname: Toshimitsu
authors.forename: Takeshi
authors.initials: T
authors.lastname: Zendo
authors.forename: Jiro
authors.initials: J
authors.lastname: Nakayama
authors.forename: Kenji
authors.initials: K
authors.lastname: Sonomoto
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001430:Bacteriocins / Q000494:pharmacology*; D002462:Cell Membrane / Q000187:drug effects; D017665:Hydroxyl Radical / Q000378:metabolism*; D013294:Lactococcus lactis / Q000187:drug effects* / Q000378:metabolism*; D008563:Membrane Lipids / Q000378:metabolism; D008564:Membrane Potentials / Q000187:drug effects; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects; D010376:Pediococcus / Q000187:drug effects; D013890:Thiourea / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D001430:Bacteriocins; D008563:Membrane Lipids; C548356:lacticin Q, Lactococcus lactis; D017665:Hydroxyl Radical; D013890:Thiourea