The PhoP/PhoQ System and Its Role in Serratia marcescens Pathogenesis

BARCHIESI, J.; CASTELLI, M. E.; DI VENANZIO, G.; COLOMBO, M.I.; GARCÍA VÉSCOVI, E.

JOURNAL OF BACTERIOLOGY

AMER SOC MICROBIOLOGY

Lugar: Washington; Año: 2012 vol. 124 p. 2949 - 2961

0021-9193

Serratia marcescens is able to invade, persist, and multiply inside nonphagocytic cells, residing in nonacidic, nondegradative,autophagosome-like vacuoles. In this work, we have examined the physiological role of the PhoP/PhoQ system and its functionin the control of critical virulence phenotypes in S. marcescens. We have demonstrated the involvement of the PhoP/PhoQ systemin the adaptation of this bacterium to growth on scarce environmental Mg2, at acidic pH, and in the presence of polymyxinB. We have also shown that these environmental conditions constitute signals that activate the PhoP/PhoQ system. We havefound that the two S. marcescens mgtE orthologs present a conserved PhoP-binding motif and demonstrated that mgtE1 expressionis PhoP dependent, reinforcing the importance of PhoP control in magnesium homeostasis. Finally, we have demonstratedthat phoP expression is activated intracellularly and that a phoP mutant strain is defective in survival inside epithelial cells. Wehave shown that the Serratia PhoP/PhoQ system is involved in prevention of the delivery to degradative/acidic compartments.