Fungi in human culture

Fermentation

Yeasts have been used since ancient times to leaven bread and to ferment beer and wine. More recently, fungi have been used for a wide variety of industrial fermentations, whether working directly for their effects on materials such as processing paper pulp or bioremediating industrial waste, or serving as the source of enzymes for many purposes, such as fading and softening denim for fashionable blue jeans. Fungi yield a wide variety of industrial enzymes including amylases, invertases, cellulases and hemicellulases, pectinases, proteases, laccases, phytases, alpha-glucuronidases, mannanases, and lipases.

Food

The fruiting bodies of many larger fungi such as the chanterelle and the cep are collected as edible mushrooms. Some, such as truffles, are esteemed as costly delicacies. A few species such as Agaricus bisporus and oyster mushrooms (Pleurotus spp.) are cultivated.

Mould fungi are the source of the meaty (umami) flavour of the soybean products tempeh, miso and soy sauce. Tempeh has been produced in Java since the 13th century. Like tofu, it is made into protein-rich blocks, but these have a firm texture and earthy flavour, since (unlike tofu) the whole beans are retained, providing a higher content of dietary fibre and vitamins. Miso too is rich in protein, vitamins and minerals. It is fermented from a mixture of soybeans and cereals, forming a soft paste used to flavour soups and other Japanese dishes. Soy sauce has been used in China since the 2nd century AD, and is now widespread in Asia. Like miso, it is made by fermenting a mixture of soybeans and cereals with moulds such as Aspergillus oryzae.

The mould Penicillium roqueforti contributes the blue coloration and much of the flavour in blue cheeses such as Roquefort and Stilton. Mould fungi are processed to produce vegetarian meat substitutes such as Quorn.

In modern medicine

Fungi are the sources of many types of medicinal drug including antibiotics, immunosuppressants, and statins. Major classes of antibiotics, the penicillins and the cephalosporins, are derived from substances produced by fungi. So also are the immunosuppressant macrolides, the cyclosporins.

The cholesterol-lowering drugs, the statins, were initially produced by fungi including Penicillium. The first commercial statin, lovastatin, was fermented by the mould Aspergillus terreus.

Numerous anti-cancer drugs such as the mitotic inhibitors vinblastine, vincristine, podophyllotoxin, griseofulvin, aurantiamine, oxaline, and neoxaline are produced by fungi.

In folk medicine

Many fungi have been used as folk medicines around the world, including in Europe and in India where traditions are well documented. Some have been found to have useful active ingredients, though these do not always correspond with traditional uses of the fungi concerned. Ergot and various cereal smuts, such as Ustilago tritici (wheat grain smut) were used for disorders of pregnancy. Yeasts, made into a boiled paste with wheat flour, were used in India to treat fevers and dysentery. Wounds were treated in Europe with moulds, using for example a slice of mouldy bread or mouldy wheat straw, with active ingredients patulin and other penicillin-like compounds.

In science

The yeast species Saccharomyces cerevisiae has been an important model organism in modern cell biology for much of the twentieth century, and is one of the most thoroughly researched eukaryotic microorganisms. It was the first eukaryote whose genome was sequenced. In the twentyfirst century, the filamentous mould Aspergillus has been adopted for genome studies.

In pest control

Entomopathogenic fungi infect and kill insects, including a variety of pest species, so they have been investigated as possible biological control agents. A variety of Ascomycetes, including Beauveria, Lecanicillium, Metarhizium, and Paecilomyces have promising features for use as biological insecticides. Metarhizium in particular can help to control outbreaks of locusts.

In religion, art, and witchcraft

Some species such as the fly agaric and psilocybin mushrooms are used for the psychoactive drugs that they contain. These are the focus of academic study and intense debate in the field of ethnomycology. In the 1950s, the American banker Robert Gordon Wasson participated in a Mazatec psilocybin mushroom ritual, and wrote an influential but controversial book claiming that the Soma mentioned in the Rigveda was Amanita muscaria, the fly agaric. The mycologist John Ramsbottom however confirmed one element that Allegro later wove into his theory, stating in 1953 that the tree of the knowledge of good and evil fresco in the Plaincourault Chapel depicted Amanita muscaria. The ergot fungi whose sclerotia appear as "black grain" in rye and other cereals are implicated in the witch trials of 17th century Norway. The hallucinations caused by ergotism, with visions of Satan as a black dog or cat, caused people to be accused of witchcraft. People in other cultures such as the Aztecs brewed drinks with ergot, which contains alkaloids based on lysergic acid.

Food spoilage

Fungi, especially moulds but also yeasts, are important agents of food spoilage. Penicillium moulds cause soft rot such as of apples, while Aspergillus moulds create patches on the surface of old bread, yoghurt and many other foods. Yeasts spoil sugary foods such as plums and jams, fermenting the sugars to alcohol. Scientific understanding of spoilage began in the 19th century with works such as Louis Pasteur's 1879 Studies on Fermentation, which investigated the spoilage of beer.

Destruction of timber

Saprotrophic wood-decay fungi are the primary cause of decomposition of wood, causing billions of dollars of economic damage each year. Fungal decay, while useful in composting, is destructive of timber exposed to the weather, and in the case of dry rot caused by Serpula lacrymans, also of timbers in largely dry houses. Some wood-decay fungi such as the honey fungi, species of Armillaria, are parasites of living trees, attacking their roots and eventually killing them, and continuing to decompose the wood when they are dead. Honey fungus is a serious horticultural pest, as it can spread from tree to tree by long strap-shaped rhizomorphs in the soil.

Diseases of crops

Fungi are important crop pathogens, as they reproduce rapidly, affect a wide range of crops around the world, cause some 85% of plant diseases, and can create serious economic losses. The range of types of fungi involved is also wide, including Ascomycetes such as Fusarium causing wilt, Basidiomycetes such as Ustilago causing smuts and Puccinia causing cereal rusts, and Oomycetes such as Phytophthora causing potato late blight and the resulting Great Irish Famine of 1845-1849. Where crop diversity is low, and in particular where single varieties of major crops are nearly universal, fungal diseases can cause the loss of an entire crop, as with the potato in Ireland, and as with the monocultured crop of maize (corn) in the USA in 1970, where over a billion dollars' worth of production was lost. Similarly, the 'Gros Michel' seedless banana crop was essentially completely destroyed worldwide in the 1950s by the wild fungus, Fusarium oxysporum. It was replaced by the Cavendish banana, which in turn was in 2015 facing total destruction by the same disease.

Diseases of humans and livestock

Pathogenic fungi cause a variety of diseases in humans and livestock. Aspergillosis, most commonly caused by Aspergillus fumigatus, kills some 600,000 people per year, mostly those with already weakened immune systems. Pneumocystis causes pneumonia, again mainly in people with weakened immune systems. Candida yeasts are the agents of Candidiasis, causing infections of the mouth, throat, and genital tract, and more seriously of the blood. Ringworm is a skin infection that infects some 20% of the human population; it is caused by some 40 different fungi.