Fungi imperfecti

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Fungi imperfecti

The fungi imperfecti, or imperfect fungi, are fungi which do not fit into the commonly established taxonomic

Taxonomy

Taxonomy is the practice and science of classification. The word comes from the Greek language ', taxis and ', nomos .Taxonomies, or taxonomic schemes, are composed of taxonomic units known as taxa , or kinds of things that are arranged frequently in a hierarchical structure....
classifications of fungi that are based on biological species concepts or morphological characteristics of sexual structures because their sexual form of reproduction has never been observed; hence the name "imperfect fungi." Only their asexual form of reproduction is known, meaning that this group of fungus produces their spores asexually.

The Deuteromycota (Greek

Greek language

Greek is an Indo-European languages native to the southern Balkan peninsula, the language of the Greek people. It forms an independent branch within Indo-European....
for "second fungi") were once considered a formal phylum

Phylum

A phylum "Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. is a taxonomic rank below Kingdom and above Class ....
of the kingdom

Kingdom (biology)

In Biology taxonomy, kingdom or regnum is a taxonomic rank in either the highest rank, or the Rank below domain . Each kingdom is divided into smaller groups called Phylum ....
Fungi.

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Encyclopedia

The fungi imperfecti, or imperfect fungi, are fungi which do not fit into the commonly established taxonomic

Taxonomy

Greek language

Phylum

A phylum "Phylum" is adopted from the Greek phylai, the clan-based voting groups in Greek city-states. is a taxonomic rank below Kingdom and above Class ....
of the kingdom

Kingdom (biology)

In Biology taxonomy, kingdom or regnum is a taxonomic rank in either the highest rank, or the Rank below domain . Each kingdom is divided into smaller groups called Phylum ....
Fungi. The term is now used only informally, to denote species of fungi that are asexually reproducing members of the fungal phyla, Ascomycota

Ascomycota

The Ascomycota are a Phylum of the kingdom Fungi, and subkingdom Dikarya, whose members are commonly known as the Sac Fungi. They are the largest phylum of Fungi, with over 30,000 species....
and Basidiomycota

Basidiomycota

Basidiomycota is one of two large phylum that, together with the Ascomycota, comprise the subkingdom Dikarya within the Kingdom Fungi. More specifically the Basidiomycota include mushrooms, puffballs, stinkhorns, bracket fungi, other polypores, jelly fungi, boletes, cantharellus, Geastraceae, smut , common bunt, rust , mirror yeasts, and the...
.

There are about 25,000 species that have been classified in the deuteromycota. Fungi producing the antibiotic penicillin

Penicillin

Penicillin is a group of antibiotics derived from Penicillium fungi. They are Beta-lactam antibiotics used in the treatment of bacterial infections caused by susceptible, usually Gram-positive, organisms....
and those that cause athlete's foot

Athlete's foot

Athlete's foot is a fungal infection of the skin that causes scaling, flaking, and itching of affected areas. It is typically transmitted in moist areas where people walk barefoot, such as showers or bathhouses....
and yeast infection

Candida (genus)

Candida is a genus of yeasts. Many species of this genus are endosymbionts of animal hosts including humans. While usually living as Commensalisms, some Candida species have the potential to cause disease....
s are imperfect fungi. In addition, there are a number of edible imperfect fungi, including the ones that provide the distinctive characteristics of Roquefort and Camembert cheese.

Other, more informal, names besides Deuteromycota ("Deuteromycetes") and fungi imperfecti, are anamorphic fungi, or mitosporic fungi, but these are terms without taxonomic rank.

Problems in taxonomic classification

Although Deuteromycota is no longer formally accepted as a taxon

Taxon

A taxon or taxonomic unit is a name designating an organism or a group of organisms. In biological nomenclature according to Carl Linnaeus, a taxon is assigned a taxonomic rank and can be placed at a particular level in a systematic hierarchy reflecting evolutionary relationships....
, many of the fungi it included have yet to find a place in modern fungal classification. This is because most fungi are classified based on characteristics of the fruiting bodies and spores produced during sexual reproduction, and members of the Deuteromycota have only been observed to produce asexual or no spores.

For this reason, mycologists are unique among those who study extant organisms in using a dual system of nomenclature. Dual naming is permitted by Article 59 of the International Code of Botanical Nomenclature

International Code of Botanical Nomenclature

The International Code of Botanical Nomenclature is the set of rules and recommendations dealing with the formal botanical names that are given to plants....
(which governs the naming of plants and fungi). Under this system, a name for an asexually reproducing fungus is considered a form taxon. For example, the ubiquitous and industrially important mold, Aspergillus niger
Aspergillus niger

Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food....
, has no known sexual cycle. Thus Aspergillus niger is considered a form taxon. In contrast, isolates of its close relative, Aspergillus nidulans
Aspergillus nidulans

Aspergillus nidulans is one of many species of filamentous fungi in the phylum Ascomycota. It has been an important research organism for studying Eukaryote cell biology...
, revealed it to be the anomorphic stage of a teleomorph already named Emericella nidulans. When a teleomorphic stage is known, that name will take priority over the name of an anamorph, hence this formerly classified Aspergillus species is now properly called Emericella nidulans.

Phylogeny and taxonomy

Phylogenetic classification of asexually reproducing fungi now commonly uses molecular systematics. Phylogenetic tree

Phylogenetic tree

A phylogenetic tree or evolutionary tree is a tree showing the evolutionary relationships among various biological species or other entities that are believed to have a common descent....
s constructed from comparative analyses of DNA sequence

DNA sequence

A DNA sequence or genetic sequence is a succession of letters representing the primary structure of a real or hypothetical DNA molecule or strand, with the capacity to carry information as described by the central dogma of molecular biology....
s, such as rDNA

Ribosomal DNA

Ribosomal DNA are sequences encoding RRNA. These sequences regulate amplification and Transcription_ initiation and contain transcribed and nontranscribed spacer segments....
, or multigene phylogenies may be used to infer relationships between asexually reproducing fungi and their sexually reproducing counterparts. With these methods, many asexually reproducing fungi have now been placed in the tree of life. However, because phylogenetic methods require sufficient quantities of biological materials (spores or fresh specimens) that are from pure (i.e., uncontaminated) fungal cultures, for many asexual species their exact relationship with other fungal species has yet to be determined. Under the current system of fungal nomenclature, teleomorph names cannot be applied to fungi that lack sexual structures. Classifying and naming asexually reproducing fungi is the subject of ongoing debate in the mycological community.

Historical classification of the Imperfect Fungi

These groups are no longer formally accepted because they do not adhere to the principle of monophyly

Monophyly

In common cladistic usage, a monophyletic group is a clade, consisting of an ancestor and all its descendants. The term is synonymous with the uncommon term holophyly....
. The taxon names are sometimes used informally. In particular, the term 'hyphomycetes' is often used to refer to molds, and the term 'coelomycetes' is used to refer to many asexually reproducing plant pathogens that form discrete fruiting bodies. Other systems of classification are reviewed by Kendrick (1981).

Class Hyphomycetes
Hyphomycetes

Hyphomycetes is a class of fungi in the phylum Deuteromycota that lack fruiting bodies. Identification of the Hyphomycetes is primarily based on microscopic morphology including: conidial morphology , especially septation, shape, size, colour and cell wall texture, the arrangement of conidia as they are borne on the conidiogenous cells , the...
lacking fruiting bodies

Order Moniliales (producing spores on simple conidiophores)
Order Stilbellales (producing spores on synnemata
Synnema

A Synnema is a large, erect reproductive structure borne by some fungi. Conidiophores fuse together to form a strand resembling a stalk of wheat, with conidia at the end or on the edges....
)
Order Tuberculariales (producing spores in sporodochia
Sporodochium

A sporodochium is a small, compact stroma usually formed on host plants parasitism by mitosporic fungi of the form order Tuberculariales . This stroma bears the conidiophores on which the asexual reproduction spores or conidium are formed....
)

Class Coelomycetes spores produced in fruiting bodies

Order Melanconiales (producing spores in acervuli
Acervulus

An acervulus is a small asexual reproduction fruiting body that erupts through the epidermis of host plants parasitism by mitosporic fungi of the form order Melanconiales ....
)
Order Sphaeropsidales (producing spores in pycnidia
Pycnidium

A pycnidium is an asexual reproduction fruiting body produced by mitosporic fungi in the form order Sphaeropsidales . It is often spherical or inversely pearshaped and its internal cavity is lined with conidiophores....
)

Class Agonomycetales lacking spores

Common Species

Industrially-relevant Fungi

Tolypocladium inflatum ? from which we obtain the immunosupressant ciclosporin
Ciclosporin

Ciclosporin , cyclosporine or cyclosporin , is an immunosuppressant medication widely used in Allograft organ transplant to reduce the activity of the patient's immune system and so the risk of organ Transplant rejection....
;
Penicillium notatum and P. chrysogenum
Penicillium griseofulvum
Penicillium roqueforti
Penicillium roqueforti

Penicillium roqueforti is a common saprotrophic fungus from the family Trichocomaceae. Widespread in nature, it can be isolated from soil, decaying organic matter, and plants....
Penicillium camemberti
Penicillium camemberti

Penicillium camemberti is a fungus used in the production of Camembert and Brie cheeses, on which colonies of P. camemberti forms a hard, white crust. It helps to give Camembert its distinctive taste....
Other species of Penicillium are used to improve both the taste and the texture of cheese
Cheese

Cheese is a food consisting of proteins and fat from milk, usually the milk of cattle, Water Buffalo, goats, or sheep's milk. It is produced by Coagulation of the milk protein casein....
s
Aspergillus oryzae
Aspergillus oryzae

Aspergillus oryzae is a hypha fungus used in Chinese cuisine and Japanese cuisine which fermentation soybeans to produce soy sauce and miso....
Aspergillus sojae
Aspergillus niger
Aspergillus niger

Aspergillus niger is a fungus and one of the most common species of the genus Aspergillus. It causes a disease called black mold on certain fruits and vegetables such as grapes, onions, and peanuts, and is a common contaminant of food....
Cladosporium resinae
Veticillium sp. and Meria sp. ? these produce conidia
Conidium

Conidia, sometimes termed conidiospores, are Asexual reproduction, non-motile spores of a fungus; they are also called mitospores due to the way they are generated through the cellular process of mitosis....
which can kill some kinds of Nematode
Nematode

The "roundworms" or "nematodes" are the most diverse phylum of body cavity, and one of the most diverse of all animals. Nematode species are very difficult to distinguish; over 80,000 have been described, of which over 15,000 are parasite....
s;

Bibliography

Gams, W. 1995. How natural should anamorph genera be? Canadian Journal of Botany 73 (suppl 1):S747-S753.
Kendrick, B. 1981. The history of conidial fungi, Pages 3-18 in GT Cole and B Kendrick, eds. Biology of Conidial Fungi. New York, Academic Press.
Seifert, KA. 1993. Integrating anamorphic fungi into the fungal system, Pages 79-85 in DR Reynolds, and JW Taylor, eds. The Fungal Holomorph: mitotic, meiotic and pleomorphic speciation in fungal systematics. Wallingford, UK, CAB International.
Taylor, JW. 1995. Making the Deuteromycota redundant: a practical integration of mitosporic and meiosporic fungi. Canadian Journal of Botany 73 (suppl 1):S754-S759.