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 constitute 1% of all described fungal species.
Basidiomycota is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya within the kingdom Fungi. Members are known as basidiomycetes. More specifically, Basidiomycota includes these groups: agarics, puffballs, stinkhorns, bracket fungi, other polypores, jelly fungi, boletes, chanterelles, earth stars, smuts, bunts, rusts, mirror yeasts, and Cryptococcus, the human pathogenic yeast.
A mold or mould is one of the structures that certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi. Not all fungi form molds. Some fungi form mushrooms; others grow as single cells and are called microfungi.
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 was reserved for the yeasts. Most yeast species formerly referred to Cryptococcus have now been placed in different genera. The name Cryptococcus comes from the Greek for "hidden sphere". Some Cryptococcus species cause a disease called cryptococcosis.
Cryptococcus neoformans is an encapsulated yeast belonging to the class Tremellomycetes and an obligate aerobe that can live in both plants and animals. Its teleomorph is a filamentous fungus, formerly referred to Filobasidiella neoformans. In its yeast state, it is often found in bird excrement. Cryptococcus neoformans can cause disease in apparently immunocompetent, as well as immunocompromised, hosts.
The Tremellomycetes are a class of dimorphic fungi in the Agaricomycotina. Some species have gelatinous basidiocarps or (microscopically) a sacculate parenthesome. There are six orders, 17 families, and 39 genera in the Tremellomycetes. Tremellomycetes include yeasts, dimorphic taxa, and species that form complex fruiting bodies. Tremellomycetes include some fungi that are human and animal pathogens in the genera Cryptococcus, Naganishia, Papiliotrema, and Trichosporon and some fungi that are cultivated for food in the genera Tremella and Naematelia.
Pathogenic fungi are fungi that cause disease in humans or other organisms. Although fungi are eukaryotic, many pathogenic fungi are microorganisms. Approximately 300 fungi are known to be pathogenic to humans; their study is called "medical mycology". Fungal infections kill more people than either tuberculosis or malaria—about 2 million people per year.
Homothallic refers to the possession, within a single organism, of the resources to reproduce sexually; i.e., having male and female reproductive structures on the same thallus. The opposite sexual functions are performed by different cells of a single mycelium.
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 hosts. Basidiocarps, when produced, are gelatinous.
Herman Jan Phaff was a scientist who specialised in yeast ecology. He was born in the Netherlands before moving to California at age of 26. He was active in Californian universities until his death. During his career he accumulated thousands of strains of yeast from the wild, and described 60 new taxa of yeast.
Candida tropicalis is a species of yeast in the genus Candida. It is a common pathogen in neutropenic hosts, in whom it may spread through the bloodstream to peripheral organs. For invasive disease, treatments include amphotericin B, echinocandins, or extended-spectrum triazole antifungals.
Phaeotremella foliacea is a species of fungus in the family Phaeotremellaceae. It produces brownish, frondose, gelatinous basidiocarps and is parasitic on the mycelium of Stereum sanguinolentum, a fungus that grows on dead attached and recently fallen branches of conifers. It is widespread in north temperate regions. In the UK it has the recommended English name leafy brain and has also been called jelly leaf and brown witch's butter. Prior to 2017, the name Tremella foliacea was also applied to similar-looking species on broadleaf trees, now distinguished as Phaeotremella frondosa and Phaeotremella fimbriata.
Pseudotremella is a genus of fungi in the family Bulleraceae. All Pseudotremella species are parasites of other fungi and produce anamorphic yeast states. Basidiocarps, when produced, are gelatinous and are colloquially classed among the "jelly fungi". Four species of Pseudotremella are currently recognized worldwide. Two of these species are, as yet, only known from their yeast states.
Naganishia is a genus of fungi in the family Filobasidiaceae. Species are currently only known from their yeast states, most of which were formerly referred to the genus Cryptococcus. Some 15 species have been described worldwide. Naganishia albida is an occasional human pathogen.
Naganishia vishniacii is an extremophile fungus originally isolated as a yeast from soil samples in the dry valleys of Antarctica. The species grows at 4 degrees Celsius and below but not at 26 degrees Celsius and above. Visually it is characterized as a cream mass in culture. It is nonfermentative and assimilates glucose, maltose, melezitose, trehalose, and xylose. Molecular research, based on cladistic analysis of DNA sequences, shows that the species does not belong in the Cryptococcaceae.
Naganishia antarctica is a yeast species that has been isolated from soil in Antarctica.
Naganishia albidosimilis is a species of fungus in the family Filobasidiaceae. It is currently only known from its yeast state, isolated from soil in Antarctica.
Naganishia albida is a species of fungus in the family Filobasidiaceae. It is currently only known from its yeast state. The species was originally isolated from the air in Japan, and has subsequently been isolated from dry moss in Portugal, grasshoppers in Portugal, and tubercular lungs.
Solicoccozyma aeria is a species of fungus in the family Piskurozymaceae. It has only been found in its yeast state, though a filamentous state producing basidia may be formed in culture.
Tremella yokohamensis is a species of fungus in the family Tremellaceae. It produces white, foliaceous, gelatinous basidiocarps and is parasitic on other fungi on dead wood of broad-leaved trees. It was originally described from Japan.
