The Amoeba Dictyostelium discoideum Contributes to Legionella Infection

The haploid social amoeba Dictyostelium discoideum is a well-defined model organism which is amenable to diverse biochemical, cell biological, and molecular genetic approaches. The similarities between the Dictyostelium and mammalian cells extend to membrane trafficking, endocytic transit and sorting events. Therefore, Dictyostelium opens the exciting possibility of investigating and manipulating both sides of the Legionella-host interaction. The intrinsic features of Dictyostelium and a set of well-established molecular tools enabled the authors to prove that Dictyostelium is a representative cellular model for Legionella infection. The research areas presented in this chapter include the analysis of the transcriptional host cell response to Legionella infection and the use of custom tailored Dictyostelium mutant cells to identify determinants of susceptibility and resistance. In order to describe the transcriptional host cell response to Legionella infection, the authors employed DNA-microarrays which carried approximately half of the Dictyostelium genes. Mammalian Nramp1 decorates endosomes, phagosomes, and postlysosomal vesicles of macrophages, and in D. discoideum it has been shown that Nramp1 depletes iron from the phagolysosome in an ATP-dependent process. Three approaches were used to analyze the complex cross-talk between Legionella and Dictyostelium. First, Dictyostelium microarrays were used to study the systemic host response to Legionella infection. Second, fluorescently tagged host cell factors were used to get new insights into the temporal and dynamic interactions between the pathogen and the host. Third, custom tailored mutants and specific inhibitors were used to functionally analyze infection relevant determinants of host susceptibility and resistance.