|1091-1||THE TYPE SIX SECRETION SYSTEMS ENCODED IN PATHOGENICITY ISLANDS SPI-6 AND SPI-19 FROM SALMONELLA DUBLIN ARE EXPRESSED BUT ARE NOT ESSENTIAL FOR BACTERIAL SURVIVAL WITHIN MURINE MACROPHAGES.|
|Autores:||Bernardo Pinto (U DE CHILE - Universidad de Chile) ; Lorenzo Leiva (U DE CHILE - Universidad de Chile) ; Paula Mardones (U DE CHILE - Universidad de Chile) ; Sergio Alvarez (U DE CHILE - Universidad de Chile) ; Carlos Blondel (U DE CHILE - Universidad de Chile) ; Carlos Santiviago (U DE CHILE - Universidad de Chile) ; Ines Contreras (U DE CHILE - Universidad de Chile) |
Introduction: Protein secretion systems are crucial to the interaction of pathogenic bacteria with host cells. The type VI secretion system (T6SS) is the most recently discovered and is widely distributed in Gram negative bacteria. In the genus Salmonella we have identified five phylogenetically distinct T6SSs, which are differentially distributed among the diverse serovars. Among these, Salmonella enterica serovar Dublin, a bovine adapted pathogen, is one of the few serovars that contain two T6SSs encoded in pathogenicity islands SPI-6 and SPI-19, respectively. In this work we have investigated whether one or both T6SS are expressed within cultured murine macrophages and whether they play a role in the survival of the bacteria within these cells.
Methods: Expression of the T6SS component VgrG was studied by infecting RAW 254.7 macrophages with S. Dublin strains containing transcriptional or translational fusions to the open reading frame for the green fluorescence protein (GFP) and transformed with pmCherry plasmid. After fixation, samples were analyzed in an epifluorescence microscope. For survival assays, gentamicin protection experiments with the wild type and isogenic mutants carrying deletions of each or both SPIs and of the ClpV component were carried out.
Results: Our results show that both VgrGs codified in the S. Dublin genome are expressed inside murine macrophages at early times after infection. However, neither SPI-6 T6SS nor SPI-19 T6SS contribute to survival of the bacteria within murine macrophages, since similar levels of bacteria were recovered from the infected macrophages irrespective of the presence or absence of the secretion systems.
Conclusions: These results indicate that the T6SSs codified within SPI-6 and SPI-19 of S. Dublin are expressed inside murine macrophages, but neither of them play a role in the survival of S. Dublin within the cells.
This work was supported by grant 1100092 from FONDECYT
Palavras-chave: Type VI Secretion System, Pathogenesis, Salmonella Dublin