Mold is a type of fungus that often grows on food. Like mushrooms, mildews, and all other fungi, molds have no chlorophyll—the green coloring matter that plants use to manufacture food. Molds live on food made by plants or animals, or on decaying matter. Some molds live as parasites on animals, plants, or other fungi.
Many common molds can grow on bread, fruit, and other food. The black bread mold often forms a cottony, soft, white growth on damp bread. The mold gets its name from the dark-colored structures called fruiting bodies that it soon produces. Fruiting bodies contain cells called spores that the mold uses to reproduce. A group of molds known as the blue molds also may grow on bread. A green mold often grows on certain cheeses. Other molds called water molds live in water and soil.
Molds develop from spores. When a spore of the black bread mold settles on damp food, it swells and begins to grow by producing tiny hyphae (threads). The hyphae form a tangled mass called a mycelium, which in turn produces aerial hyphae called stolons. Rootlike structures known as rhizoids anchor stolons in the food.
As the black bread mold matures, many upright fruiting bodies form above the rhizoids. Each fruiting body has a spore case called a sporangium at its end. A sporangium looks like a miniature pinhead and contains thousands of spores. When the spore case matures and breaks open, the spores are carried away by air currents or other means. These spores may settle on damp foods and grow, starting the reproductive cycle over again. Some molds, including penicillium, produce chains of spores at the tips of hyphae called conidiophores.
Moldy foods generally should be thrown away. But certain cheeses, such as Roquefort, owe their flavor to a mold that grows in them and ripens them. Molds are also useful because they fertilize soil by breaking up dead organisms and waste material. Penicillium molds produce the drug penicillin (see Penicillin ).
