Characterization of Legionella pneumophila genes with impact on bacterial uptake into host cells and on bacterial virulence

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Legionella pneumophila is an intracellularly replicating bacterium and the causative agent of Legionnaires' disease. Successful parasitism of host cells involves efficient adherence and entry of the bacteria. Some of the Legionella adherence- and uptake-promoting factors have been already described, however specific underlying mechanisms have not been extensively evaluated. In our prework, we screened 11,300 transposon-mutagenized L. pneumophila clones in an amoebae-infection model and we identified 98 apathogenous clones. Selected mutants were furthermore tested for adherence/uptake properties in macrophages and seven clones were found dramatically deficient. In two of the clones, the transposon hit well known Legionella adherence/uptake genes, but five genes in that respect were novel. Three of those five genes have not yet been functionally evaluated for L. pneumophila. The aim of the presented study is therefore to examine whether the respective proteins directly or indirectly contribute to bacterial adherence/uptake processes. Furthermore, one selected protein will be purified, its effect on uptake processes examined, and its eukaryotic interaction partner will be identified. Additionally, the protein localization during bacterial growth in laboratory medium and in eukaryotic cells will be determined and in parallel the changes in host cell cytoskeleton due to the protein will be monitored.