Lifecycle of Francisella tularensis in human macrophages. F. tularensis enters human macrophages by looping phagocytosis and quickly comes to reside in a membrane-bound phagosome. Many of these phagosomes acquire a unique densely staining fibrillar coat on their cytoplasmic surface. The fibrillar coat and phagosome membrane subsequently fragment, releasing the bacterium to the cytoplasm of the host cell. Subsequently, the bacterium multiplies intracytoplasmically.