Legionella pneumophila, an opportunistic bacterial pathogen responsible for Legionnaire's disease, reproduces inside specialized vacuoles after phagocytosis by its host cells—either free-living protozoa or human macrophages. Legionella-containing vacuoles do not fuse with other endocytic vesicles but instead recruit vesicles from the early secretory pathway. They modify the vacuole membrane by using a type IV secretion system, which transports effector proteins made by the bacterium into the host cell.
Weber et al. examined the role of host-derived phosphoinositides (PIs) in intracellular replication and found that they are important in the anchoring of secreted bacterial effector proteins inside the vacuole. Specific effector proteins interact with a variety of host-derived PIs and, in particular, recruit PI(4) phosphate in order to attach themselves to the vacuolar membrane. Mutant bacteria lacking functional type IV secretion systems fail to modulate host cell PI metabolism and are degraded. — SMH
PLoS Pathog. 2, e46 (2006).