Economic Importance of Fungi

Fungi are not all rot and ruin; many are quietly useful. Yeast, a single-celled fungus, ferments sugar into carbon dioxide and alcohol. The gas makes bread dough rise into soft loaves, while the alcohol is the basis of brewing. The mould Penicillium gives us penicillin, the first antibiotic, and also ripens cheeses such as Roquefort. Aspergillus niger is grown in factories to make citric acid for soft drinks, and edible mushrooms like Agaricus are eaten worldwide as a tasty, protein-rich food.

An antibiotic is a chemical made by a living microorganism that can stop the growth of, or kill, disease-causing bacteria. Alexander Fleming noticed that the mould Penicillium killed bacteria around it, and from this came penicillin. Antibiotics let doctors cure infections that were once deadly. This single discovery is one of the most important gifts of fungi to medicine.

The same kingdom also causes trouble. Bread mould (Rhizopus) and other fungi spoil our food, growing on bread, fruit, pickles, leather and cloth in warm, damp conditions and making them unfit to use. Some fungi attack the body directly: ringworm and athlete's foot are fungal skin diseases. Others ruin harvests, with rusts and smuts of wheat and the late blight of potato destroying whole crops. Damp houses with no sunlight grow mould easily, which is why direct sunlight is healthy, as the ultraviolet rays kill mould spores.

Even the spoiling habit of fungi has a useful side. As saprophytes, fungi break down dead leaves, wood and the bodies of dead organisms, returning their nutrients to the soil and keeping it fertile. So decay is harmful when it destroys our food and goods, but essential when it recycles nature's waste. Fungi sit on both sides of the ledger at once, which is exactly why we study their economic importance.