Penicillium fungus, photo of colonies of Penicillium fungi grown on Sabouraud Dextrose Agar and computer illustration of fungal morphology. Penicillium fungus causes food spoilage and produces the antibiotic penicillin. There are over 100 species of Penicillium. Air-borne spores alight on food and germinate, absorbing nutrients for growth via radiating filaments called hyphae. Each mass of hyphae, called a mycelium, generates aerial branches bearing fruiting bodies consisting of new spores. These appear green in the case of Penicillium and green, blue, yellow or black in the case of other Plectascales. The new spores are dispersed by air movements.