Figure 1

Histoplasma capsulatum is a dimorphic fungal pathogen. Histoplasma capsulatum grows as a saprophytic mold in the soil (left) but, upon inhalation by a mammalian host, converts to a pathogenic yeast form (center) capable of intracellular growth within host macrophages (right). Both small and large vegetative spores (micro and macroconidia, respectively) are depicted in the mold form. Within the macrophage, yeast cells are shown within a membrane-bound phagosome, and the macrophage nucleus is also depicted.