The O'Connor Lab studies the molecular basis of infectious disease using Legionella pneumophila pathogenesis as a model system. We are looking at the network of molecular interactions acting at the host-pathogen interface. Specifically, we use L. pneumophila pathogenesis to examine the numerous mechanisms by which an intracellular bacterial pathogen can establish infection, how it exploits host cell machinery to accomplish this, and how individual proteins and their component pathways coordinately contribute to disease. We are also studying the role of environmental hosts in the evolution of human pathogens. Using genetics and functional genomics, we compare and contrast the repertoires of virulence proteins required for growth in a broad assortment of hosts, how the network of molecular interactions differs between hosts, and the mechanisms by which L. pneumophila copes with this variation.