Serratia marcescens MODULATION OF AUTOPHAGY AND THE ROLE OF ShlA HAEMOLYSIN

DI VENANZIO GISELA; FEDRIGO, GRISELDA; CAMPOY, EMANUEL MARTIN; COLOMBO MARIA ISABEL; VESCOVI, ELEONORA

Puerto Madryn

Congreso; XLVI SAIB; 2010

Serratia marcescens is an opportunistic pathogen important for public health. However, little is known about factors and mechanisms that contribute to Serratia pathogenesis. In this work, we demonstrated that the majority of the autophagic‐like vacuoles in which Serratia resides and proliferates are non‐acidic and have no degradative properties. No detectable increase of intracellular CFUs was detected when we induced autophagy by starvation; nevertheless, theywere drastically diminished when wortmannin was used to block autophagy. In the last condition, microscopical inspection revealed that the scarce intracellular compartments harboring Serratia were positive for LC3 and packed with bacteria, exhibiting identical phenotype to the SeCVs. A Serratia mutant with impeded activation and secretion of the ShlA haemolysin was unable to induce autophagy from outside the CHO cells. Based on these findings, we propose that a) S. marcescens is capable to either delay or hamper the fusion to lysosomal compartments; b) ShlA expression is responsible for the autophagic phenotype induced by Serratia in epithelial cells; and c) wortmannin was unable to inhibit the autophagic process triggered by Serratia, although it could hinder bacterial internalization, indicating that PI3K activity is required for the Serratia internalization process into CHO cells.