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Journal of Bacteriology, July 2008, p. 4951-4958, Vol. 190, No. 14
0021-9193/08/$08.00+0     doi:10.1128/JB.00195-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

mgtA Expression Is Induced by Rob Overexpression and Mediates a Salmonella enterica Resistance Phenotype

Julieta Barchiesi, María E. Castelli, Fernando C. Soncini, and Eleonora García Véscovi^*

Instituto de Biología Molecular y Celular de Rosario, Consejo Nacional de Investigaciones Científicas y Técnicas (IBR-CONICET), Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, Universidad Nacional de Rosario, S2002LRK Rosario, Argentina

Received 7 February 2008/ Accepted 7 May 2008

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.

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* Corresponding author. Mailing address: Instituto de Biología Molecular y Celular de Rosario (IBR-CONICET), Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas (UNR) Suipacha 531, S2002LRK Rosario, Argentina. Phone: 54-341-4356369, ext. 131. Fax: 54-341-4804598. E-mail: garciavescovi{at}ibr.gov.ar

Published ahead of print on 16 May 2008.

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Journal of Bacteriology, July 2008, p. 4951-4958, Vol. 190, No. 14
0021-9193/08/$08.00+0     doi:10.1128/JB.00195-08
Copyright © 2008, American Society for Microbiology. All Rights Reserved.

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