Mold is the common name of many types of fungi and funguslike protists; the fuzzy growths these organisms form are also called molds. The growths consist of numerous individual molds growing in colonies. Some molds are saprophytes; they live on dead organisms such as decaying plants or animals and on nonliving organic substances such as food, paper, and fabrics. Other molds are parasites; they obtain nourishment from a live host.
Molds have many harmful effects. For example, molds often grow on breads, pastries, jellies, and dairy products. They can damage stored grain, fruit and vegetables, and livestock feed, thereby causing serious financial loss to farmers. They can also cause diseases, such as gray mold, in garden plants. Athlete’s foot as well as other types of ringworm are skin diseases caused by parasitic molds. Mold growth is prevented by maintaining dry, airy surroundings; by heat-radiation techniques in the processing of food; and by using fungicides.
Molds, however, also have many beneficial effects. They are instrumental in the decay of dead things, thereby aiding in the elimination of debris. Molds are the source of such antibiotics as penicillin. Molds are used in making such cheeses as Roquefort and Camembert and in the commercial production of such biochemicals as enzymes and hormones.