MGTA EXPRESSION IS INDUCED BY ROB AND MEDIATES Salmonella CYCLOHEXANE RESISTANCE

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

Villa Carlos Paz

Congreso; XLIV Reunión anual- Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

SAIB

mgtA codes for a P-type ATPase which is known as one of the three2+ Mg transporters in Salmonella enterica, It has been previouslydemonstrated that mgtA expression is regulated at the2+ transcriptional level by the extracellular Mg -responsivePhoP/PhoQ two-component system and post-transcriptionally by2+ an intracellular Mg -sensitive riboswitch. In our laboratory, whilesearching for factors that would modulate the expression ofSalmonella mgtA, independently of the PhoP/PhoQ system, weidentified Rob. Rob is a member of the a subfamiliy of AraC/XylStypetranscriptional regulators implicated in bacterial multidrug,heavy metal, superoxide and organic solvent resistance phenotypes.We demonstrate that, in Salmonella, Rob expression (but not itsparalog proteins SoxS or MarA) is able to induce mgtA transcriptionin a PhoP-independent fashion by binding to a conservedrob/mar/sox motif localized downstream the PhoP-box, andoverlapping the PhoP-dependent transcriptional start site. We foundthat Rob-induced mgtA expression confers Salmonella a low-levelcyclohexane resistance. Because mgtA intactness is required forRob-induced cyclohexane resistance provided the AcrABmultidrug efflux pump can be expressed, we postulate that MgtA isinvolved in the AcrAB-mediated cyclohexane detoxificationmechanism promoted by Rob expression, disclosing a novel role forMgtA in Salmonella.