A Microbial Biorealm page on the Basidiomycota
Higher order taxa:
Eukaryota; Fungi/Metazoa group; Fungi
Agaricus bisporus, Rhodotorula creatinivora, Cryptococcus neoformans
Description and Significance
Basidiomycota is a classification that describes a wide variety of organisms. It is estimated that there are about 30,000 species, and more species are being discovered all the time. For example, the work of Geml et. al (2005) and Bergauer et al. (2005) has led to the discovery of several new species. While it is best known for fruitbodies such as mushrooms, puffballs, and brakcets, it also contains microscopic fungi. These include rust fungi and smut fungi, which are both parasites. Bastidiomycota makes up about 37% of fungi. These fungi are considered to be the most evolutionarily advanced of all other fungi species. However, these are not the only species within this classification. Like ascomycota, Bastidiomycota is also home to some forms of yeast. Therefore, the organisms within this classification can be either unicellular or multicellular. There are three major groups within this classification. The first is Urediniomycetes, which includes rusts and other taxa. Second is Ustilaginomycetes, which are largely composed of smuts. Last is the Hymenomycetes, which are comprised of mushrooms and jelly fungi.
An important characteristic of Bastidiomycota is that of ballistospores. This is a method of reproduction which propels spores directly into the air. This ability probably evolved early on. These spores may be sexual or asexual. However, most aquatic forms of bastidiomycota have lost the ability to produce ballistospores.
One of the unusual types of Basidiomycota are the gasteromycetes. These are most commonly known as puffballs. Earthstars are fruitbodies of Geastrum, and are similar to puffballs. They often grow below ground in woodland areas. Bird's Nest Fungi are another unusual species. They typically grow on wood chippings.
Like ascomycota, Basidiomycota contain numerous species of fungi and yeast, and the genetic structures of each are very different.
Cell Structure and Metabolism
All hyphae that make up toadstools are dikaryotic. There is a type of structure unique to Bastidiomycota called clamp connections. They form when dikaryotic hyphae divide. However, not all Basidiomycota produce them. It is believed that clamp connections developed early on in evolutionary history.
Bastidiomycota acquire energy by decaying wood, plant, and waste.
Most bastidiospores with friutbodies will not produce these bodies until environmental cues tell them to. Basidomycota contain both sexual and asexual species. The spores usually germinate from haploid, uninucleate cells. Sexual reproduction is the fusion of haploid cells. Basidiospores within the organism usually have a single haploid nucleus. The hyphae are termed monkaryons. Eventually, two monokaryons fuse; this fusion is referred to as plasmogamy. After plasmogamy occurs, the nuclei divide and the daughter nuclei pair, creating a dikaryon. Once a fruitbody is produced, some hyphae create bastidia (cells that are the site of sexual spore production), which eventually fuse in a process called karyogamy. Usually this results in the production of four new spores.
Bastidiomycota can be found in almost every terrestrial environments. They are also located in aquatic environments, both with freshwater and marine habitats. Their contributions to the decay of plant and waste materials make them an important factor in the carbon cycle. However, the decay also has negative impacts for humans if they attack wood structures such as houses. The economic consequences have led researchers and corporations to study wood-eating fungi. D.Q. Yang, of Forintek Canada Corporation, researched the types of fungi and molds that affect trees (2005). By isolating fungi and mold species from sugar maple, yellow birch, and white birch wood, Yang attempted to discover whether or not these species were host specific. He found that the majority of the species were not host specific; they would attack any type of wood. Some of the most frequently isolated molds and fungi in this study were: Alternaria alternata, Ophiostoma piceae, Ophiostoma piliferum, and Nectria cinnabarina.
Some species of Basidiomycota are pathogens for both plants and animals. However, they are not all harmful. Some form symbiotic relationships with the roots of vascular plants. The bastidiomycota help the plants obtain nutrients from the soil, and in return recieve sugars produced through photosynthesis. Bastidiomycota also form symbiotic relationships with insects.
While mushrooms are used for food, there are also many other uses humans have for Basidiomycota. For example, the toxin phalloidin, found in the mushroom Amanita phalloides, is incorporated into flourescent stains that are used by cell biologists to view the cytoskeleton. Certain wood-decaying enzymes are used in paper production. Some people use the chemicals provided by mushrooms for hallucinogenic purposes. These are often for spiritual reasons, but also make up a part of the illicit drug trade.
One of the unusual formations of Basidiomycota are known as fairy rings. Fungi grows on dead leaves and roots in grasslands, and produce rings of fruiting bodies or mushrooms. The rings expand every year and release nitrogen into the soil, creating very lush grass. These rings expand every year. Folkloric legends associated these rings with fairy dances, which is how they got their name. Most do not damage the grass, but some fungi, such as Marasmius oreades (also known as the fairy ring champignon) will kill the areas beneath it. They accomplish this by forming water-repellent masses of hyphae beneath the soil, dehydrating the grass.
The fairy ring is not just of interest to scientists or landscapers. Its presence within folkloric traditions has given the fairy ring representations in art and literature. Moselio Schaechter has a large collection of mushrooms represented in visual art. This, of course, includes fairy rings. The pictures he has of fairy rings are not necessarily technical or scientific in their representations, but instead draw on mythological ideas.
Ale-Agha N, Feige GB, Jensen M, Christiaans B, Brassmann M, Kricke R. "New, rare or remarkable microfungi in the Italian Alps (Carnic Alps)--part II--other microfungi." Communications in agricultural and applied biological sciences. 2004;69(4):467-77.
Bergauer P, Fonteyne PA, Nolard N, Schinner F, Margesin R. "Biodegradation of phenol and phenol-related compounds by psychrophilic and cold-tolerant alpine yeasts.Chemosphere. 2005 May;59(7):909-18. Epub 2004 Dec 21.
Geml J, Davis DD, Geiser DM. "Phylogenetic analyses reveal deeply divergent species lineages in the genus Sphaerobolus (Phallales: Basidiomycota)." Molecular phylogenetics and evolution. 2005 May;35(2):313-22.