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

BARCHIESI, JULIETA; CASTELLI, MARÍA EUGENIA; GARCIA VESCOVI ELEONORA

Puerto Madryn

Congreso; XLVI Reunión Anual- Sociedad Argentina de investigación en Bioquímica y Biología Molecular; 2010

SAIB

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 PhoPQ 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, b-galactosidase assays revealed that phoP transcription was modulated by the Mg2+ and Polymyxin B levels, predicted to be environmental signals detected by the system. Furthermore, the phoP strain was attenuated 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 wild type strain. Nevertheless, in contrast with the observed in S. marcescens wild type, phoP mutant containg vacuoles colocalized with acidic compartment marker lysotraker, suggesting they couldn’t evade lysosome fusion and degradation. Our results suggest that PhoPQ system is crucial in S. marcescens virulence, regulating process that might support intracellular survival inside the host and lysosomal fusion avoidance.