Characterization of the PhoP/PhoQ system in S. marcescens and its role in pathogenesis.

JULIETA BARCHIESI; MARÍA E. CASTELLI; ELEONORA GARCÍA VÉSCOVI

Puerto Madryn

Congreso; XLVI reunión Anual - Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2010

The opportunistic human pathogen Serratia marcescens is a significant cause of hospital-acquired infection. However, few reports have explored in depth the mechanisms that contribute to S. marcescens pathogenesis within its host. In this work, we analyzed the role of the PhoP/PhoQ two component system in S. marcescens virulence. We demonstrated that phoP mutant exhibited impaired growth in minimal broth limited in Mg2+, in acid pH, and showed increased sensitivity to antimicrobial peptides than the wild type strain. In addition, beta -galactosidase assays revealed that phoP transcription was modulated by the Mg2+ and Polymyxin B levels. Furthermore, the phoP strain was diminished in the survival inside epithelial cells, despite the fact that confocal microscopy analysis revealed that phoP mutant was able to enter and multiply into vacuoles in epithelial cells similarly to the wild type strain. Nevertheless, and in contrast to wild type S. marcescens, the vast majority of the vacuoles harbouring the phoP mutant strain colocalized with the acidic compartment marker Lysotraker, suggesting that they could not evade lysosome fusion and degradation. Our results indicate that the PhoP/PhoQ system is crucial in S. marcescens virulence, regulating processes that are involved in supporting intracellular survival and lysosomal fusion avoidance inside the host epithelial cells.