engleski

Intracellular trafficking of Francisella tularensis subsp. novicida within Dictyostelium discoideum

Francisella tularensis is a gram-negative bacterium able to replicate in mammalian, arthropod and amoeba cells. Dictyostelium discoideum is a soil amoeba that has been used to study virulence factors for many bacterial pathogens, including Legionella pneumophila, Mycobacterium spp., Pseudomonas aeruginosa, Klebsiella pneumoniae, and Salmonella typhimurium. It has been shown that F. tularensis is able to survive and replicate in Acanthamoeba castellanii and Hartmanella vermiformis. Since there are limited opportunities to study intracellular life cycle of Francisella in amoebae cells we used D. discoideum to explore the intracellular trafficking of F. novicida in these cells. First, we show that growth of Francisella is depended on the presence of D. discoideum in the medium. F. novicida replicates exponentially within D. discoideum cells and is fatal to the cells a dose-dependent manner, while the iglC mutant is severely defective. Using electron and fluorescence microscopy-based phagosome integrity assays, we show that bacterium does not escape into the cytosol of D. discouidem but it replicates in the membrane-bound vacuoles. Endocytic trafficking studies of F. novicida within D. discoideum show co-localization of the bacterial phagosome with D. discoideum vatA but not with vacuolin. The data show that Francisella-containing vacuole harboring the iglC mutant acquire vacuolin, indicating merging with the lysosomal compartments. Our data indicate crucial differences in the intracellular trafficking of F. novicida within mammalian and D. discoideum cells.

Francisella; trafficking; Dictyostelium

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