The causative agent of Legionnaires' Disease, Legionella pneumophila, is an intracellular bacterial pathogen with a remarkably broad host range. In the environment, L. pneumophila replicates inside a variety of freshwater protozoan hosts. As such, Legionella has evolved to be a "professional" cell biologist - targeting conserved eukaryotic pathways in order to replicate inside host cells. Our primary focus is on understanding the evolutionary processes that have made Legionella into the pathogen it is today and the mechanisms that the bacteria use to manipulate eukaryotic pathways.