NEW INSIGHTS INTO THE CONTROL OF MAGNESIUM HOMEOSTASIS IN Salmonella enterica

SPINELLI, SILVANA; LUCAS PONTEL; ELEONORA GARCÍA VÉSCOVI,; FERNANDO C. SONCINI

Bariloche, Argentina

Congreso; Argentine Society for Biochemistry and Molecular Biology XXXIX Annual Meeting, Biophysical Society of Argentina XXXII Annual Meeting; 2003

SAIB-SAB

Magnesium plays a fundamental role in Salmonella pathogenesis.  It controls the activation of the PhoP/PhoQ regulatory system, signaling the bacteria its specific location inside the host.  In response to Mg2+ limitation, the PhoP/PhoQ regulatory system triggers the expression of two high-affinity Mg2+ transporter genes, mgtA and mgtCB.  Mutations in mgtA or in mgtCB greatly affect the ability of Salmonella to grow in low Mg2+ environments. We uncovered a novel checkpoint in the Mg2+ deprivation response.  This mechanism can detect this cellular stress bypassing PhoQ and posing an additional control over the expression of the Mg2+ transporters.  We have demonstrated that in mgtA the responsive element for the PhoQ-independent regulatory mechanism maps to the 5?UTR.  We further characterized this region using site directed mutagenesis, and examined the level (transcriptional/posttranscriptional) at which this system exerts its control.  The study of this homeostatic network will provide new insights in the mechanisms that allow Salmonella to proliferate within its host.