Microbe Profile: Legionella pneumophila - a copycat eukaryote.

Legionella pneumophila is an environmental bacterium that parasitizes aquatic protozoa and uses the same processes to infect humans. The facultative intracellular pathogen causes a life-threatening pneumonia with possible systemic complications. The co-evolution with protozoa is reflected in an armoury of bacterial effectors, and many of these type IV-secreted proteins have likely been acquired by interdomain horizontal gene transfer (HGT) from hosts. The unique features of L. pneumophila are the largest bacterial effector repertoire known to date, subversion of virtually all eukaryotic signalling pathways and acquisition of eukaryotic enzyme activities used to manipulate the host cell to the pathogen's advantage.