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

BARCHIESI, JULIETA; CASTELLI, MARÍA EUGENIA; SONCINI, FERNANDO; GARCÍA VÉSCOVI, ELEONORA

JOURNAL OF BACTERIOLOGY

AMER SOC 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 Mg(2+) transporter. mgtA was previously characterized as a member of the Mg(2+)-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.