Rhizopus arrhizus is a fungus of the family Mucoraceae, characterized by sporangiophores that arise from nodes at the point where the rhizoids are formed and by a hemispherical columella. It is the most common cause of mucormycosis in humans and occasionally infects other animals. Rhizopus arrhizus spores contain ribosomes as a spore ultrastructure. Metabolism in the fungus changes from aerobic to fermentation at various points in its life cycle.