mgtA expression is induced by Rob overexpression and mediates a Salmonella enterica resistance phenotype

BARCHIESI, J.; CASTELLI, M. E.; SONCINI, F. C.; GARCÍA VÉSCOVI, E.

JOURNAL OF BACTERIOLOGY

American Society for Microbiology

Año: 2008 vol. 190 p. 4951 - 4958

0021-9193

Rob is a member of the Sox/Mar subfamiliy 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 up-regulates 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 proteins 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 the PhoP-box, and overlapping the PhoP-dependent transcriptional start site. We found that Rob-induced mgtA expression confers Salmonella a low-level cyclohexane resistance. 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.