CHARACTERIZATION OF THE Serratia marcescens MUTANT STRAIN IN THE GENE THAT ENCODES ShlA CYTOL

DI VENANZIO, GISELA; STEPANENKO, TATIANA; GARCÍA VÉSCOVI, ELEONORA

Mendoza

Congreso; Sociedad Argentina de Investigación en Bioquímica y Biología; 2012

Serratia mercescens ShlA hemolysin is one of the major virulence factors of this opportunistic pathogen. ShlA presents cytotoxic activity in several cellular lines and we have demonstrated that ShlA expression is controlled by the Rcs system. A Serratia marcescens mutant strain with impeded activation and secretion of ShlA was unable to induce autophagy from outside the CHO cells. However, intracelullary, this strain was found inside a LC3-positive vacuole. An increase of intracellular CFUs was detected at late times in the invasion process in either T24 or CHO epithelial cells, when compared to wild type strain. Nevertheless and in contrast to the wt strain, no mutant bacteria were detected in the culture supernatant when gentamicin was eliminated from the assay at late times p.i. In addition, intracellular CFUs of the mutant strain were highly diminished as early as 120 min p.i. in Bafilomycin A1 or NH4Cl treated cells, as it was also determined for the wt strain. In summary, our results reveal that: a) ShlA expression is responsible for the autophagic phenotype induced by in epithelial cells from the extracellular space, b) at late times p.i., ShlA is required to mediate the exit and dissemination of from the invaded cell, and c) ShlA is not implicated in early internalization and replication processes that would require an acidic environment to take place.