The Tremellales are an

order Order, ORDER or Orders may refer to: * Categorization, the process in which ideas and objects are recognized, differentiated, and understood * Heterarchy, a system of organization wherein the elements have the potential to be ranked a number of ...

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 ...

in the

class Class or The Class may refer to: Common uses not otherwise categorized * Class (biology), a taxonomic rank * Class (knowledge representation), a collection of individuals or objects * Class (philosophy), an analytical concept used differently ...

Tremellomycetes The Tremellomycetes are a class of dimorphic fungi in the Agaricomycotina. Some species have gelatinous basidiocarps (fruiting bodies) or (microscopically) a sacculate parenthesome. There are six orders, 17 families, and 39 genera in the Tremell ...

. The order contains both teleomorphic and

anamorph In mycology, the terms teleomorph, anamorph, and holomorph apply to portions of the life cycles of fungi in the phyla Ascomycota and Basidiomycota: *Teleomorph: the sexual reproductive stage (morph), typically a fruiting body. *Anamorph: an a ...

species In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is often defined as the largest group of organisms in which any two individuals of the appropriat ...

, most of the latter being

yeasts Yeasts are eukaryotic, single-celled microorganisms classified as members of the fungus kingdom. The first yeast originated hundreds of millions of years ago, and at least 1,500 species are currently recognized. They are estimated to constitut ...

. All teleomorphic species in the Tremellales are

parasites Parasitism is a close relationship between species, where one organism, the parasite, lives on or inside another organism, the host, causing it some harm, and is adapted structurally to this way of life. The entomologist E. O. Wilson ha ...

of other fungi, though the yeast states are widespread and not restricted to hosts.

Basidiocarps In fungi, a basidiocarp, basidiome, or basidioma () is the sporocarp of a basidiomycete, the multicellular structure on which the spore-producing hymenium is borne. Basidiocarps are characteristic of the hymenomycetes; rusts and smuts do not ...

(fruit bodies), when produced, are gelatinous. The order currently comprises 11 families, containing around 250 valid species. Significant

genera Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...

include ''

Tremella ''Tremella'' is a genus of fungi in the family Tremellaceae. All ''Tremella'' species are parasites of other fungi and most produce anamorphic yeast states. Basidiocarps (fruit bodies), when produced, are gelatinous and are colloquially classed ...

'', one species of which is edible and commercially cultivated, and the yeast genus ''

Cryptococcus ''Cryptococcus'' is a genus of fungi in the family Cryptococcaceae that includes both yeasts and filamentous species. The filamentous, sexual forms or teleomorphs were formerly classified in the genus ''Filobasidiella'', while ''Cryptococcus'' ...

'', several species of which are human

pathogen In biology, a pathogen ( el, πάθος, "suffering", "passion" and , "producer of") in the oldest and broadest sense, is any organism or agent that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a g ...

History

The order Tremellales was created (as 'Tremellinae') by Swedish mycologist

Elias Magnus Fries Elias Magnus Fries (15 August 1794 – 8 February 1878) was a Swedish mycologist and botanist. Career Fries was born at Femsjö ( Hylte Municipality), Småland, the son of the pastor there. He attended school in Växjö. He acquire ...

in 1821 for fungi having gelatinous fruit bodies. it was amended in 1922 by English mycologist

Carleton Rea Carleton Rea (7 May 1861 – 26 June 1946) was an English mycologist, botanist, and naturalist. Background and education Carleton Rea was born in Worcester, the son of the City Coroner. He was educated at The King's School and Magdalen Colle ...

to include all species, gelatinous or not, in which the

basidia A basidium () is a microscopic sporangium (a spore-producing structure) found on the hymenophore of fruiting bodies of basidiomycete fungi which are also called tertiary mycelium, developed from secondary mycelium. Tertiary mycelium is highly- ...

were "tremelloid" (globose to ellipsoid with vertical or diagonal septa). Rea placed within it one family, the

Tremellaceae The Tremellaceae are a family of fungi in the order Tremellales. The family is cosmopolitan and contains both teleomorphic and anamorphic species, most of the latter being yeasts. All teleomorphs in the Tremellaceae are parasites of other fungi, ...

, having the same characteristics as the order. Rea's circumscription was generally accepted until the 1980s. In 1945, however, G.W. Martin proposed a substantial extension of the order to include all the species within the (now obsolete) class

Heterobasidiomycetes Heterobasidiomycetes, including jelly fungi, smuts and rusts, are basidiomycetes with septate basidia. This contrasts them to homobasidiomycetes (alternatively called holobasidiomycetes), including most mushrooms and other Agaricomycetes, whic ...

except for the rusts and the smuts. Martin therefore included within the Tremellales not only the Tremellaceae, but also the Auriculariaceae,

Dacrymycetaceae The Dacrymycetaceae are a family of fungi in the order Dacrymycetales. Species are saprotrophs and occur on dead wood. Their distribution is worldwide. Basidiocarps (fruit bodies) are ceraceous to gelatinous, often yellow to orange, and variousl ...

, Hyaloriaceae, Phleogenaceae, Septobasidiaceae,

Sirobasidiaceae The Sirobasidiaceae are a family of fungi in the order 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 teleomo ...

, and

Tulasnellaceae The Tulasnellaceae are a family of fungi in the order Cantharellales. The family comprises mainly effused (patch-forming) fungi formerly referred to the " jelly fungi" or heterobasidiomycetes. Species are wood- or litter-rotting saprotrophs, but ...

(including ''

Ceratobasidium ''Ceratobasidium'' is a genus of fungi in the order Cantharellales. Basidiocarps (fruit bodies) are effused and the genus is sometimes grouped among the corticioid fungi, though species also retain features of the heterobasidiomycetes. Anamorphic ...

''). This extended version of the order was not widely adopted, but was used in a number of publications by Martin himself and, as late as the 1970s, by his student Bernard Lowy. A more precise revision was undertaken in 1984, when Robert Bandoni used

transmission electron microscopy Transmission electron microscopy (TEM) is a microscopy technique in which a beam of electrons is transmitted through a specimen to form an image. The specimen is most often an ultrathin section less than 100 nm thick or a suspension on a ...

to investigate the ultrastructure of the septal pore apparatus in species of the Tremellales. This revealed that ''

'' and its allies were distinct from ''

Exidia ''Exidia'' is a genus of fungi in the family Auriculariaceae. The species are saprotrophic, occurring in attached or recently fallen dead wood, and produce gelatinous basidiocarps (fruit bodies). The fruit bodies are diverse, pustular, lobed, bu ...

'' and its allies, despite both groups having tremelloid basidia. Bandoni referred the latter group to the

Auriculariales The Auriculariales are an order of fungi in the class Agaricomycetes. Species within the order were formerly referred to the " heterobasidiomycetes" or "jelly fungi", since many have gelatinous basidiocarps (fruit bodies) that produce spores on s ...

, restricting the Tremellales to the Tremellaceae, Sirobasidiaceae, and Tetragoniomycetaceae.

Current status

Molecular A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bio ...

research, based on

cladistic Cladistics (; ) is an approach to biological classification in which organisms are categorized in groups ("clades") based on hypotheses of most recent common ancestry. The evidence for hypothesized relationships is typically shared derived char ...

analysis of

DNA sequences A nucleic acid sequence is a succession of bases signified by a series of a set of five different letters that indicate the order of nucleotides forming alleles within a DNA (using GACT) or RNA (GACU) molecule. By convention, sequences are us ...

, confirms Bandoni's split between the tremelloid and exidioid fungi and extends the circumscription of the tremelloid group by including several yeast genera whose status was formerly uncertain. Molecular research has also indicated that the genus ''

'' should be included within the group, even though species do not have tremelloid basidia.

References

{{Taxonbar, from=Q206636 Tremellomycetes Basidiomycota orders