Intracellular survival of Streptococcus pneumoniae depends on lysosomal acidification and the two-component system ComDE.

CIAN, M.; CORTES, P.; YANDAR BARAHONA, N.; ECHENIQUE, J

Mendoza

Congreso; SAIB; 2012

SAIB

It has been described that the uptake of pneumococcus involved clathrin coated-vesicles, and bacteria proceed into vacuoles decorated by Rab5 and Rab7, the classical route to the lysosome. However, there is no data about the existence of a specific pneumococcal containing-vacuole and the intracellular life of this pathogen. Using an in vitro infection model, we observed a decrease in the number of intracellular bacteria in the first hours, although it remains alive in macrophages and pneumocytes for at least 5 hours. By immunofluorescence microscopy, long bacterial chains were observed intracellularly. In macrophages, inhibition of lysosomal acidification by chloroquine increased bacterial clearance, suggesting that bacterial survival mechanism depends on lysosomal pH. On the other hand, we focused our study in bacterial mechanisms that would allow pneumococcus to survive inside cells, for example, signal transduction systems. We carried out survival assays using two-component systems mutants, and we found that the comE mutant evaded bacterial clearance and replicates inside the pneumocytes. These results suggested that pneumococcus was able to survive within macrophages and pneumocytes for several hours, and that its survival mechanism depends on lysosomal acidification. In addition, we showed that ComE is involved in controlling survival/death balance of pneumococcus inside cells.