title: mgtA Expression is induced by rob overexpression and mediates a Salmonella enterica resistance phenotype.
abstract: Rob is a member of the Sox/Mar subfamily of AraC/XylS-type transcriptional regulators implicated in bacterial multidrug, heavy metal, superoxide, and organic solvent resistance phenotypes. We demonstrate that, in Salmonella enterica, Rob overexpression upregulates the transcription of mgtA, which codes for the MgtA Mg2+ transporter. mgtA was previously characterized as a member of the Mg2+-modulated PhoPQ regulon. Here we demonstrate that Rob (but not its paralog protein SoxS or MarA) is able to induce mgtA transcription in a PhoP-independent fashion by binding to a conserved Mar/Sox/Rob motif localized downstream of the PhoP-box and overlapping the PhoP-dependent transcriptional start site. We found that Rob-induced mgtA expression confers low-level cyclohexane resistance on Salmonella. Because mgtA intactness is required for Rob-induced cyclohexane resistance, provided the AcrAB multidrug efflux pump can be expressed, we postulate that MgtA is involved in the AcrAB-mediated cyclohexane detoxification mechanism promoted by Rob in Salmonella.
authors.affiliation: Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas (UNR), Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Rosario, Argentina.
authors.forename: Julieta
authors.initials: J
authors.lastname: Barchiesi
authors.forename: María E
authors.initials: ME
authors.lastname: Castelli
authors.forename: Fernando C
authors.initials: FC
authors.lastname: Soncini
authors.forename: Eleonora García
authors.initials: EG
authors.lastname: Véscovi
mesh_terms: D000251:Adenosine Triphosphatases / Q000096:biosynthesis*; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D003510:Cyclohexanes / Q000494:pharmacology; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D024881:Drug Resistance, Bacterial; D024901:Drug Resistance, Multiple, Bacterial; D018628:Gene Dosage; D005786:Gene Expression Regulation; D026901:Membrane Transport Proteins / Q000096:biosynthesis*; D019216:Metals, Heavy / Q000494:pharmacology; D008969:Molecular Sequence Data; D011485:Protein Binding; D012486:Salmonella typhimurium / Q000502:physiology*; D024363:Transcription Initiation Site; D015854:Up-Regulation
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D003510:Cyclohexanes; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D026901:Membrane Transport Proteins; D019216:Metals, Heavy; C506365:Cyclohexane; D000251:Adenosine Triphosphatases; C093585:MgtA protein, bacteria