Filobasidiella
Encyclopedia
Filobasidiella is a genus
of fungi in the family
Tremellaceae
. Species are parasitic on other fungi and do not produce distinct basidiocarps (fruit bodies). The genus is the teleomorphic (sexual) state of the yeast
genus Cryptococcus
, some species of which are human pathogens.
, Filobasidiella neoformans, by crossing strains of the yeast Cryptococcus neoformans
. She was able to observe basidia similar to those of the genus Filobasidium, hence the name Filobasidiella for the new genus.
Based on the shape and structure of the basidia, the genus was initially assigned to the order
Filobasidiales
. Cladistic analysis of DNA sequences, however, later showed that Filobasidiella belonged within the Tremellales
, with the genus Kwoniella
(with Tremella-like basidia) as a sister clade.
or unclamped, and bear haustorial cells with filaments that attach to the hyphae of the host fungus. The basidia are club-shaped and highly elongated. Spores arise in succession from four loci at the apex (which is sometimes partly septate). These spores are passively released and may remain on the basidium in chains, unless disturbed. In the type species, the spores germinate to form yeast cells, but yeast states are not known for all species.
Filobasidiella neoformans and F. bacillispora are known only from laboratory cultures of their respective yeast states (Cryptococcus neoformans and Cryptococcus gattii
). The presence of haustorial cells on their hyphae indicate that they are (or were) parasites of other fungi, but their original host species are unknown. Both yeasts are human pathogens, responsible for cryptococcosis
, and are now cosmopolitan
in distribution.
Filobasidiella depauperata (synonym F. arachnophila) is parasitic on Lecanicillium lecanii
, an entomopathogenic fungus
, and is known from Sri Lanka
, England
, the Netherlands
, the Czech Republic
, and Canada
. It is not known to produce a yeast state. Filobasidiella lutea is parasitic on Granulobasidium vellereum
, a corticioid fungus, and is known from England
and Italy
. It too is not known to produce a yeast state. DNA sequencing suggests all four species are congeneric. A fifth species, Filobasidiella xianghuijun, has been reported from China
in association with Tremella fuciformis, but its status is uncertain.
Genus
In biology, a genus is a low-level taxonomic rank used in the biological classification of living and fossil organisms, which is an example of definition by genus and differentia...
of fungi in the family
Family (biology)
In biological classification, family is* a taxonomic rank. Other well-known ranks are life, domain, kingdom, phylum, class, order, genus, and species, with family fitting between order and genus. As for the other well-known ranks, there is the option of an immediately lower rank, indicated by the...
Tremellaceae
Tremellaceae
The Tremellaceae are a family of fungi in the order Tremellales. The family is cosmopolitan and contains both teleomorphic and anamorphic genera, most of the latter being yeasts. All teleomorphic species of fungi in the Tremellaceae are parasites of other fungi, though the yeast states are...
. Species are parasitic on other fungi and do not produce distinct basidiocarps (fruit bodies). The genus is the teleomorphic (sexual) state of the yeast
Yeast
Yeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with 1,500 species currently described estimated to be only 1% of all fungal species. Most reproduce asexually by mitosis, and many do so by an asymmetric division process called budding...
genus Cryptococcus
Cryptococcus
Cryptococcus is a genus of fungus. Species grow in culture as yeasts. The perfect forms or teleomorphs of Cryptococcus species are filamentous fungi in the genus Filobasidiella...
, some species of which are human pathogens.
History
The genus was first described in 1975 from the USA by K.J. Kwon-Chung, who obtained cultures of the type speciesType species
In biological nomenclature, a type species is both a concept and a practical system which is used in the classification and nomenclature of animals and plants. The value of a "type species" lies in the fact that it makes clear what is meant by a particular genus name. A type species is the species...
, Filobasidiella neoformans, by crossing strains of the yeast Cryptococcus neoformans
Cryptococcus neoformans
Cryptococcus neoformans is an encapsulated yeast that can live in both plants and animals. Its teleomorph is Filobasidiella neoformans, a filamentous fungus belonging to the class Tremellomycetes. It is often found in pigeon excrement....
. She was able to observe basidia similar to those of the genus Filobasidium, hence the name Filobasidiella for the new genus.
Based on the shape and structure of the basidia, the genus was initially assigned to the order
Order (biology)
In scientific classification used in biology, the order is# a taxonomic rank used in the classification of organisms. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, and species, with order fitting in between class and family...
Filobasidiales
Filobasidiales
The Filobasidiales are an order in the fungal class Tremellomycetes. The one family in the order, the Filobasidiaceae, contains four species. They are distinguished from other tremelloid species by the lack of a macroscopic basidiocarp....
. Cladistic analysis of DNA sequences, however, later showed that Filobasidiella belonged within the Tremellales
Tremellales
The Tremellales are an order of fungi in the class Tremellomycetes. The order contains both teleomorphic and anamorphic species, most of the latter being yeasts. All teleomorphic species in the Tremellales are parasites of other fungi, though the yeast states are widespread and not restricted to...
, with the genus Kwoniella
Kwoniella
Kwoniella is a genus of fungi in the family Tremellaceae. The genus is monotypic, containing the single species Kwoniella mangrovensis, found in the Florida Everglades and The Bahamas....
(with Tremella-like basidia) as a sister clade.
Description
Filobasidiella species are not known to produce distinct, visible fruitbodies. Microscopically, the hyphae are colourless, are clampedClamp connection
A clamp connection is a structure formed by growing hyphal cells of certain fungi. It is created to ensure each septum, or segment of hypha separated by crossed walls, receives a set of differing nuclei, which are obtained through mating of hyphae of differing sexual types...
or unclamped, and bear haustorial cells with filaments that attach to the hyphae of the host fungus. The basidia are club-shaped and highly elongated. Spores arise in succession from four loci at the apex (which is sometimes partly septate). These spores are passively released and may remain on the basidium in chains, unless disturbed. In the type species, the spores germinate to form yeast cells, but yeast states are not known for all species.
Habitat, Distribution, and Species
Cryptococcus gattii
Cryptococcus gattii, formerly known as Cryptococcus neoformans var gattii, is an encapsulated yeast found primarily in tropical and subtropical climates...
). The presence of haustorial cells on their hyphae indicate that they are (or were) parasites of other fungi, but their original host species are unknown. Both yeasts are human pathogens, responsible for cryptococcosis
Cryptococcosis
Cryptococcosis, or cryptococcal disease, is a potentially fatal fungal disease. It is caused by one of two species; Cryptococcus neoformans and Cryptococcus gattii. These were all previously thought to be subspecies of C...
, and are now cosmopolitan
Cosmopolitan distribution
In biogeography, a taxon is said to have a cosmopolitan distribution if its range extends across all or most of the world in appropriate habitats. For instance, the killer whale has a cosmopolitan distribution, extending over most of the world's oceans. Other examples include humans, the lichen...
in distribution.
Filobasidiella depauperata (synonym F. arachnophila) is parasitic on Lecanicillium lecanii
Verticillium
Verticillium is a genus of fungi in the division Ascomycota, and are an anamorphic form of the Plectosphaerellaceae family. The genus used to include diverse groups comprising saprobes and parasites of higher plants, insects, nematodes, mollusc eggs and other fungi thus it can be seen that the...
, an entomopathogenic fungus
Entomopathogenic fungus
An entomopathogenic fungus is a fungus that can act as a parasite of insects and kills or seriously disables them.-Typical life cycle:These fungi usually attach to the external body surface of insects in the form of microscopic spores...
, and is known from Sri Lanka
Sri Lanka
Sri Lanka, officially the Democratic Socialist Republic of Sri Lanka is a country off the southern coast of the Indian subcontinent. Known until 1972 as Ceylon , Sri Lanka is an island surrounded by the Indian Ocean, the Gulf of Mannar and the Palk Strait, and lies in the vicinity of India and the...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...
, the Czech Republic
Czech Republic
The Czech Republic is a landlocked country in Central Europe. The country is bordered by Poland to the northeast, Slovakia to the east, Austria to the south, and Germany to the west and northwest....
, and Canada
Canada
Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...
. It is not known to produce a yeast state. Filobasidiella lutea is parasitic on Granulobasidium vellereum
Granulobasidium vellereum
Granulobasidium vellereum is a species of fungus in the Cyphellaceae family. A plant pathogen associated with white rot of angiospermous logs, slash, and living trees, it has been found in Sweden and Denmark, and in North America. Originally described as Corticium vellereum in 1885, it was...
, a corticioid fungus, and is known from England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
and Italy
Italy
Italy , officially the Italian Republic languages]] under the European Charter for Regional or Minority Languages. In each of these, Italy's official name is as follows:;;;;;;;;), is a unitary parliamentary republic in South-Central Europe. To the north it borders France, Switzerland, Austria and...
. It too is not known to produce a yeast state. DNA sequencing suggests all four species are congeneric. A fifth species, Filobasidiella xianghuijun, has been reported from China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
in association with Tremella fuciformis, but its status is uncertain.