title: Downregulation of RpoN-controlled genes protects Salmonella cells from killing by the cationic antimicrobial peptide polymyxin B.
abstract: Salmonella enterica polymyxin B (PM) resistance is modulated mainly by substitutions of the acyl chains and the phosphate groups on the lipid A moiety of lipopolysaccharide. These modifications are mediated by genes under the control of the PmrA/PmrB and PhoP/PhoQ two-component regulatory systems. In this study, a deletion in the gene encoding the alternative sigma(54) factor, rpoN, was shown to increase PM resistance without affecting protamine sensitivity. The results presented here showed that the increased polymyxin resistance observed in the DeltarpoN mutant occurs through a PmrA/PhoP-independent pathway. Downregulation of one or more genes belonging to the RpoN regulon may provide an additional mechanism of defence against membrane-permeabilizing antimicrobial peptides that helps the pathogen to survive in different environments.
authors.affiliation: Departamento de Microbiología, Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, Rosario, Argentina.
authors.forename: Julieta
authors.initials: J
authors.lastname: Barchiesi
authors.forename: Martín
authors.initials: M
authors.lastname: Espariz
authors.forename: Susana K
authors.initials: SK
authors.lastname: Checa
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Soncini
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects; D024881:Drug Resistance, Bacterial; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D011112:Polymyxin B / Q000494:pharmacology*; D051877:RNA Polymerase Sigma 54 / Q000235:genetics* / Q000378:metabolism; D012486:Salmonella typhimurium / Q000187:drug effects* / Q000235:genetics / Q000378:metabolism; D017384:Sequence Deletion
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D051877:RNA Polymerase Sigma 54; D011112:Polymyxin B