Microfungi or micromycetes are

fungi A fungus ( : fungi or funguses) is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. These organisms are classified as a kingdom, separately fr ...

—

eukaryotic Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacte ...

organisms such as molds, mildews and

rust Rust is an iron oxide, a usually reddish-brown oxide formed by the reaction of iron and oxygen in the catalytic presence of water or air moisture. Rust consists of hydrous iron(III) oxides (Fe2O3·nH2O) and iron(III) oxide-hydroxide (FeO( ...

s—which have microscopic

spore In biology, a spore is a unit of sexual or asexual reproduction that may be adapted for dispersal and for survival, often for extended periods of time, in unfavourable conditions. Spores form part of the life cycles of many plants, algae, ...

-producing structures. They exhibit tube tip-growth and have cell walls composed of

chitin Chitin ( C8 H13 O5 N)n ( ) is a long-chain polymer of ''N''-acetylglucosamine, an amide derivative of glucose. Chitin is probably the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chit ...

, a polymer of ''N''-acetylglucosamine. Microfungi are a

paraphyletic In taxonomy, a group is paraphyletic if it consists of the group's last common ancestor and most of its descendants, excluding a few monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In ...

group, distinguished from macrofungi only by the absence of a large, multicellular fruiting body. They are ubiquitous in all terrestrial and freshwater and marine environments, and grow in plants, soil, water, insects, cattle rumens, hair, and skin. Most of the fungal body consists of microscopic threads, called

hyphae A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one or ...

, extending through the substrate in which it grows. The

mycelia Mycelium (plural mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Fungal colonies composed of mycelium are found in and on soil and many other substrates. A typical single spore germinates in ...

of microfungi produce

s that are carried by the air, spreading the fungus. Many microfungi species are benign, existing as soil saprotrophs, for example, largely unobserved by humans. Many thousands of microfungal species occur in

lichen A lichen ( , ) is a composite organism that arises from algae or cyanobacteria living among filaments of multiple fungi species in a mutualistic relationship.symbiotic Symbiosis (from Greek , , "living together", from , , "together", and , bíōsis, "living") is any type of a close and long-term biological interaction between two different biological organisms, be it mutualistic, commensalistic, or para ...

relationships with

algae Algae (; singular alga ) is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular micr ...

. Other microfungi, such as those of the genera '' Penicillium'', '' Aspergillus'' and '' Neurospora'', were first discovered as molds causing spoilage of fruit and bread. Certain species have commercial value. ''Penicillium'' species are used in the manufacture of blue cheeses and as the source of the

antibiotic An antibiotic is a type of antimicrobial substance active against bacteria. It is the most important type of antibacterial agent for fighting bacterial infections, and antibiotic medications are widely used in the treatment and prevention ...

penicillin Penicillins (P, PCN or PEN) are a group of β-lactam antibiotics originally obtained from '' Penicillium'' moulds, principally '' P. chrysogenum'' and '' P. rubens''. Most penicillins in clinical use are synthesised by P. chrysogenum usin ...

, discovered by Sir

Alexander Fleming Sir Alexander Fleming (6 August 1881 – 11 March 1955) was a Scottish physician and microbiologist, best known for discovering the world's first broadly effective antibiotic substance, which he named penicillin. His discovery in 1928 of what ...

in 1928, while '' Fusarium venenatum'' is used to produce Quorn, a mycoprotein food product. __TOC__

Harmful microfungi

Microfungi can be harmful, causing diseases of plants, animals and humans with varying degrees of severity and economic impact. The irritating human skin disease known as athlete's foot or tinea pedis is caused by species of the microfungal genus '' Trichophyton''. Microfungi may cause diseases of crops and trees which range in severity from mild to disastrous, and in economic importance from beneficial to seriously costly. The mould ''

Botrytis cinerea ''Botrytis cinerea'' is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as "botrytis bunch rot"; in horticulture, it is usually called "grey mould" or ...

'' can cause spoilage of crops including grapes, but is also responsible for the " noble rot", which concentrates sugars in the grapes used to make the intensely sweet and concentrated Sauternes dessert wines from the

Bordeaux Bordeaux ( , ; Gascon oc, Bordèu ; eu, Bordele; it, Bordò; es, Burdeos) is a port city on the river Garonne in the Gironde department, Southwestern France. It is the capital of the Nouvelle-Aquitaine region, as well as the prefectu ...

region of

France France (), officially the French Republic ( ), is a country primarily located in Western Europe. It also comprises of Overseas France, overseas regions and territories in the Americas and the Atlantic Ocean, Atlantic, Pacific Ocean, Pac ...

Dutch elm disease Dutch elm disease (DED) is caused by a member of the sac fungi (Ascomycota) affecting elm trees, and is spread by elm bark beetles. Although believed to be originally native to Asia, the disease was accidentally introduced into America, Europe ...

, which has ravaged elms across Europe and North America in the last 50 years, is caused by the microfungi of the genus ''

Ophiostoma ''Ophiostoma'' is a genus of fungi within the family Ophiostomataceae. It was circumscribed in 1919 by mycologists Hans Sydow and Paul Sydow. Species *'' Ophiostoma adjuncti'' *'' Ophiostoma ainoae'' *'' Ophiostoma allantosporum'' *'' Ophiost ...

''. Rice blast, a devastating fungal disease of

cereal A cereal is any grass cultivated for the edible components of its grain (botanically, a type of fruit called a caryopsis), composed of the endosperm, germ, and bran. Cereal grain crops are grown in greater quantities and provide more food ...

s including

rice Rice is the seed of the grass species '' Oryza sativa'' (Asian rice) or less commonly ''Oryza glaberrima'' (African rice). The name wild rice is usually used for species of the genera '' Zizania'' and '' Porteresia'', both wild and domesticat ...

wheat Wheat is a grass widely cultivated for its seed, a cereal grain that is a worldwide staple food. The many species of wheat together make up the genus ''Triticum'' ; the most widely grown is common wheat (''T. aestivum''). The archaeologi ...

and

millet Millets () are a highly varied group of small-seeded grasses, widely grown around the world as cereal crops or grains for fodder and human food. Most species generally referred to as millets belong to the tribe Paniceae, but some millets a ...

, is caused by the

phytopathogenic Plant pathology (also phytopathology) is the scientific study of diseases in plants caused by pathogens (infectious organisms) and environmental conditions (physiological factors). Organisms that cause infectious disease include fungi, oomy ...

Ascomycete fungus '' Magnaporthe grisea''. In the

built environment The term built environment refers to human-made conditions and is often used in architecture, landscape architecture, urban planning, public health, sociology, and anthropology, among others. These curated spaces provide the setting for human ...

, the toxic fungus ''

Stachybotrys chartarum ''Stachybotrys chartarum'' (, ), also known as black mold or toxic black mold, is a species of microfungus that produces its conidia in slime heads. It is sometimes found in soil and grain, but the mold is most often detected in cellulose-rich b ...

'' causes damage to damp walls and furnishings, and may be responsible for

sick building syndrome Sick building syndrome (SBS) is an unsubstantiated diagnosis where health problems are attributed to buildings. The cause of the health problems are unknown. Symptoms attributed to SBS may or may not be a direct result of inadequate cleaning or ...

. Types of epidermal microfungal infections are: * Yeast infection * Athlete's foot * Mycosis * Tinea * Candida

Diversity

Within the United States, approximately 13,000 species of microfungi on plants or plant products are thought to exist. Specimens of microfungi are housed in the U.S. National Fungus Collections and other institutions that serve as reservoirs of information and documentation about the nation's natural heritage. Based on the number of species reported in the literature and those represented in the collections; the number of microfungi known in the United States is estimated at 29,000 species. In areas of the world where fungi have been well studied, the ratio of vascular plants to fungi is about 6 to 1. This suggests that there may be as many as 120,000 species of fungi within the United States and 1.5 million worldwide.

References

{{Reflist Fungi Fungus ecology