Isogamy is a form of sexual reproduction that involves gametes of similar morphology, differing in general only in allele expression in one or more mating-type regions. Because both gametes look alike, they cannot be classified as "male" or "female". Instead, organisms undergoing isogamy are said to have different mating types, most noted as "+" and "−" strains, although in some species of Basidiomycota there are more than two mating types. In all cases, fertilization occurs, it appears. In several lineages, this form of reproduction independently evolved to anisogamous species with gametes of male and female types to oogamous species in which the female gamete is much larger than the male and has no ability to move. There is a good argument that this pattern was driven by the physical constraints on the mechanisms by which two gametes get together as required for sexual reproduction. In Ascomycetes, anisogamy evolved from isogamy before mating types. There are several types of isogamy. Both gametes may be flagellated and thus motile.
This type occurs for example in algae such as some but not all species of Chlamydomonas. In another type, neither of the gametes is flagellated; this is the case for example in the mating of yeast. Yeast mating types are noted as "a" and "α" instead of "+" and "-". Another, more complex form, is conjugation; this occurs in some the Zygnematophyceae, e.g. Spirogyra; these algae grow as filaments of cells. When two filaments of opposing mating types come close together, the cells form conjugation tubes between the filaments. Once the tubes are formed, one cell balls up and crawls through the tube into the other cell to fuse with it, forming a zygote. In ciliates, cell fission may follow self-fertilization. In zygomycetes fungi, two hyphae of opposing mating types form special structures called gametangia where the hyphae touch; the gametangia fuse into a zygosporangium. In other fungi, cells from two hyphae with opposing mating types fuse, but only the cytoplasm is fused; the two nuclei do not fuse, leading to the formation of a dikaryon cell that gives rise to a mycelium consisting of dikaryons.
Karyogamy eventually occurs in sporangia, leads to the formation of diploid cells that undergo meiosis to form spores. In many cases, isogamous fertilization is used by organisms that can reproduce asexually through binary fission, budding, or asexual spore formation; the switch to sexual reproduction mode is triggered by a change from favorable to unfavorable growing conditions. Fertilization leads to the formation of a thick-walled zygotic resting spore that can withstand harsh environments and will germinate once growing conditions turn favorable again. Anisogamy Evolution of sexual reproduction Gamete Mating in fungi Meiosis Oogamy Sex Hypergamy Hypogamy Sa Geng. "Evolution of Sexes from an Ancestral Mating-Type Specification Parthway". PLOS Biology. Doi:10.137/journal.pbio.10001904
Basidiomycota is one of two large divisions that, together with the Ascomycota, constitute the subkingdom Dikarya within the kingdom Fungi. More Basidiomycota includes these groups: mushrooms, stinkhorns, bracket fungi, other polypores, jelly fungi, chanterelles, earth stars, bunts, mirror yeasts, the human pathogenic yeast Cryptococcus. Basidiomycota are filamentous fungi composed of hyphae and reproduce sexually via the formation of specialized club-shaped end cells called basidia that bear external meiospores; these specialized spores are called basidiospores. However, some Basidiomycota reproduce asexually in exclusively. Basidiomycota that reproduce asexually can be recognized as members of this division by gross similarity to others, by the formation of a distinctive anatomical feature, cell wall components, definitively by phylogenetic molecular analysis of DNA sequence data; the most recent classification adopted by a coalition of 67 mycologists recognizes three subphyla and two other class level taxa outside of these, among the Basidiomycota.
As now classified, the subphyla join and cut across various obsolete taxonomic groups commonly used to describe Basidiomycota. According to a 2008 estimate, Basidiomycota comprise three subphyla 16 classes, 52 orders, 177 families, 1,589 genera, 31,515 species. Traditionally, the Basidiomycota were divided into two classes, now obsolete: Homobasidiomycetes, including true mushrooms Heterobasidiomycetes, including the jelly and smut fungiPreviously the entire Basidiomycota were called Basidiomycetes, an invalid class level name coined in 1959 as a counterpart to the Ascomycetes, when neither of these taxa were recognized as divisions; the terms basidiomycetes and ascomycetes are used loosely to refer to Basidiomycota and Ascomycota. They are abbreviated to "basidios" and "ascos" as mycological slang; the Agaricomycotina include what had been called the Hymenomycetes, the Gasteromycetes, as well as most of the jelly fungi. The three classes in the Agaricomycotina are the Agaricomycetes, the Dacrymycetes, the Tremellomycetes.
The class Wallemiomycetes is not yet placed in a subdivision, but recent genomic evidence suggests that it is a sister group of Agaricomycotina. The Pucciniomycotina include the rust fungi, the insect parasitic/symbiotic genus Septobasidium, a former group of smut fungi, a mixture of odd, infrequently seen, or recognized fungi parasitic on plants; the eight classes in the Pucciniomycotina are Agaricostilbomycetes, Atractiellomycetes, Classiculomycetes, Cryptomycocolacomycetes, Cystobasidiomycetes, Microbotryomycetes and Pucciniomycetes. The Ustilaginomycotina are most of the Exobasidiales; the classes of the Ustilaginomycotina are the Exobasidiomycetes, the Entorrhizomycetes, the Ustilaginomycetes. Unlike animals and plants which have recognizable male and female counterparts, Basidiomycota tend to have mutually indistinguishable, compatible haploids which are mycelia being composed of filamentous hyphae. Haploid Basidiomycota mycelia fuse via plasmogamy and the compatible nuclei migrate into each other's mycelia and pair up with the resident nuclei.
Karyogamy is delayed, called a dikaryon. The hyphae are said to be dikaryotic. Conversely, the haploid mycelia are called monokaryons; the dikaryotic mycelium is more vigorous than the individual monokaryotic mycelia, proceeds to take over the substrate in which they are growing. The dikaryons can be decades, or centuries; the monokaryons are neither female. They have either a tetrapolar mating system; this results in the fact that following meiosis, the resulting haploid basidiospores and resultant monokaryons, have nuclei that are compatible with 50% or 25% of their sister basidiospores because the mating genes must differ for them to be compatible. However, there are sometimes more than two possible alleles for a given locus, in such species, depending on the specifics, over 90% of monokaryons could be compatible with each other; the maintenance of the dikaryotic status in dikaryons in many Basidiomycota is facilitated by the formation of clamp connections that physically appear to help coordinate and re-establish pairs of compatible nuclei following synchronous mitotic nuclear divisions.
Variations are multiple. In a typical Basidiomycota lifecycle the long lasting dikaryons periodically produce basidia, the specialized club-shaped end cells, in which a pair of compatible nuclei fuse to form a diploid cell. Meiosis follows shortly with the production of 4 haploid nuclei that migrate into 4 external apical basidiospores. Variations occur, however; the basidiospores are ballistic, hence they are sometimes called ballistospores. In most species, the basidiospores disperse and each
Ascomycota is a division or phylum of the kingdom Fungi that, together with the Basidiomycota, form the subkingdom Dikarya. Its members are known as the sac fungi or ascomycetes, it is the largest phylum of Fungi, with over 64,000 species. The defining feature of this fungal group is the "ascus", a microscopic sexual structure in which nonmotile spores, called ascospores, are formed. However, some species of the Ascomycota are asexual, meaning that they do not have a sexual cycle and thus do not form asci or ascospores. Familiar examples of sac fungi include morels, brewer's yeast and baker's yeast, dead man's fingers, cup fungi; the fungal symbionts in the majority of lichens such as Cladonia belong to the Ascomycota. Ascomycota is a monophyletic group. Placed in the Deuteromycota along with asexual species from other fungal taxa, asexual ascomycetes are now identified and classified based on morphological or physiological similarities to ascus-bearing taxa, by phylogenetic analyses of DNA sequences.
The ascomycetes are of particular use to humans as sources of medicinally important compounds, such as antibiotics, for fermenting bread, alcoholic beverages and cheese. Penicillium species on cheeses and those producing antibiotics for treating bacterial infectious diseases are examples of ascomycetes. Many ascomycetes are pathogens, both of animals, including humans, of plants. Examples of ascomycetes that can cause infections in humans include Candida albicans, Aspergillus niger and several tens of species that cause skin infections; the many plant-pathogenic ascomycetes include apple scab, rice blast, the ergot fungi, black knot, the powdery mildews. Several species of ascomycetes are biological model organisms in laboratory research. Most famously, Neurospora crassa, several species of yeasts, Aspergillus species are used in many genetics and cell biology studies. Ascomycetes: Ascomycetes are'spore shooters', they are fungi which produce microscopic spores inside special, elongated cells or sacs, known as'asci', which give the group its name.
Asexual reproduction: Asexual reproduction is the dominant form of propagation in the Ascomycota, is responsible for the rapid spread of these fungi into new areas. Asexual reproduction of ascomycetes is diverse from both structural and functional points of view; the most important and general is production of conidia, but chlamydospores are frequently produced. Furthermore, Ascomycota reproduce asexually through budding. 1) Conidia formation: Asexual reproduction may occur through vegetative reproductive spores, the conidia. The asexual, non-motile haploid spores of a fungus, which are named after the Greek word for dust, are hence known as conidiospores and mitospores; the conidiospores contain one nucleus and are products of mitotic cell divisions and thus are sometimes call mitospores, which are genetically identical to the mycelium from which they originate. They are formed at the ends of specialized hyphae, the conidiophores. Depending on the species they may be dispersed by animals. Conidiophores may branch off from the mycelia or they may be formed in fruiting bodies.
The hypha that creates the sporing tip can be similar to the normal hyphal tip, or it can be differentiated. The most common differentiation is the formation of a bottle shaped cell called a phialide, from which the spores are produced. Not all of these asexual structures are a single hypha. In some groups, the conidiophores are aggregated to form a thick structure. E.g. In the order Moniliales, all of them are single hyphae with the exception of the aggregations, termed as coremia or synnema; these produce structures rather like corn-stokes, with many conidia being produced in a mass from the aggregated conidiophores. The diverse conidia and conidiophores sometimes develop in asexual sporocarps with different characteristics; some species of Ascomycetes form their structures within plant tissue, either as parasite or saprophytes. These fungi have evolved more complex asexual sporing structures influenced by the cultural conditions of plant tissue as a substrate; these structures are called the sporodochium.
This is a cushion of conidiophores created from a pseudoparenchymatous stroma in plant tissue. The pycnidium is a globose to flask-shaped parenchymatous structure, lined on its inner wall with conidiophores; the acervulus is a flat saucer shaped bed of conidiophores produced under a plant cuticle, which erupt through the cuticle for dispersal. 2) Budding: Asexual reproduction process in ascomycetes involves the budding which we observe in yeast. This is termed a “blastic process”, it involves the blebbing of the hyphal tip wall. The blastic process can involve all wall layers, or there can be a new cell wall synthesized, extruded from within the old wall; the initial events of budding can be seen as the development of a ring of chitin around the point where the bud is about to appear. This stabilizes the cell wall. Enzymatic activity and turgor pressure act to extrude the cell wall. New cell wall material is incorporated during this phase. Cell contents are forced into the progeny cell, as the final phase of mitosis ends a cell plate, the point at which a new cell wall will grow inwards from, forms.
Ascomycota are morphologically diverse. The group includes organisms from unicellular yeasts to complex cup fungi. There are 30,000 species of Ascomycota; the unifying characteri
Saccharomyces cerevisiae is a species of yeast. It has been instrumental to winemaking and brewing since ancient times, it is believed to have been isolated from the skin of grapes. It is one of the most intensively studied eukaryotic model organisms in molecular and cell biology, much like Escherichia coli as the model bacterium, it is the microorganism behind the most common type of fermentation. S. cerevisiae cells are round to ovoid, 5–10 μm in diameter. It reproduces by a division process known as budding. Many proteins important in human biology were first discovered by studying their homologs in yeast. S. cerevisiae is the only yeast cell known to have Berkeley bodies present, which are involved in particular secretory pathways. Antibodies against S. cerevisiae are found in 60–70% of patients with Crohn's disease and 10–15% of patients with ulcerative colitis. S. cerevisiae, a yeast, have been found to contribute to the smell of bread by Schieberle. "Saccharomyces" derives from Latinized Greek and means "sugar-mold" or "sugar-fungus", saccharon being the combining form "sugar" and myces being "fungus".
Cerevisiae comes from Latin and means "of beer". Other names for the organism are: Brewer's yeast, though other species are used in brewing Ale yeast Top-fermenting yeast Baker's yeast Ragi yeast, in connection to making tapai Budding yeastThis species is the main source of nutritional yeast and yeast extract. In the 19th century, bread bakers obtained their yeast from beer brewers, this led to sweet-fermented breads such as the Imperial "Kaisersemmel" roll, which in general lacked the sourness created by the acidification typical of Lactobacillus. However, beer brewers switched from top-fermenting to bottom-fermenting yeast and this created a shortage of yeast for making bread, so the Vienna Process was developed in 1846. While the innovation is popularly credited for using steam in baking ovens, leading to a different crust characteristic, it is notable for including procedures for high milling of grains, cracking them incrementally instead of mashing them with one pass. Refinements in microbiology following the work of Louis Pasteur led to more advanced methods of culturing pure strains.
In 1879, Great Britain introduced specialized growing vats for the production of S. cerevisiae, in the United States around the turn of the century centrifuges were used for concentrating the yeast, making modern commercial yeast possible, turning yeast production into a major industrial endeavor. The slurry yeast made by small bakers and grocery shops became cream yeast, a suspension of live yeast cells in growth medium, compressed yeast, the fresh cake yeast that became the standard leaven for bread bakers in much of the Westernized world during the early 20th century. During World War II, Fleischmann's developed a granulated active dry yeast for the United States armed forces, which did not require refrigeration and had a longer shelf-life and better temperature tolerance than fresh yeast; the company created yeast that would rise twice as fast. Lesaffre would create instant yeast in the 1970s, which has gained considerable use and market share at the expense of both fresh and dry yeast in their various applications.
In nature, yeast cells are found on ripe fruits such as grapes. Since S. cerevisiae is not airborne, it requires a vector to move. Queens of social wasps overwintering as adults can harbor yeast cells from autumn to spring and transmit them to their progeny; the intestine of Polistes dominula, a social wasp, hosts S. cerevisiae strains as well as S. cerevisiae × S. paradoxus hybrids. Stefanini et al. showed that the intestine of Polistes dominula favors the mating of S. cerevisiae strains, both among themselves and with S. paradoxus cells by providing environmental conditions prompting cell sporulation and spores germination. The optimum temperature for growth of S. cerevisiae is 30–35 °C. Two forms of yeast cells can survive and grow: diploid; the haploid cells undergo a simple lifecycle of mitosis and growth, under conditions of high stress will, in general, die. This is the asexual form of the fungus; the diploid cells undergo a simple lifecycle of mitosis and growth. The rate at which the mitotic cell cycle progresses differs between haploid and diploid cells.
Under conditions of stress, diploid cells can undergo sporulation, entering meiosis and producing four haploid spores, which can subsequently mate. This is the sexual form of the fungus. Under optimal conditions, yeast cells can double their population every 100 minutes. However, growth rates vary enormously both between environments. Mean replicative lifespan is about 26 cell divisions. In the wild, recessive deleterious mutations accumulate during long periods of asexual reproduction of diploids, are purged during selfing: this purging has been termed "genome renewal". All strains of S. cerevisiae can grow aerobically on glucose and treh
Neurospora crassa is a type of red bread mold of the phylum Ascomycota. The genus name, meaning "nerve spore" in Greek, refers to the characteristic striations on the spores; the first published account of this fungus was from an infestation of French bakeries in 1843. N. Crassa is used as a model organism because it is easy to grow and has a haploid life cycle that makes genetic analysis simple since recessive traits will show up in the offspring. Analysis of genetic recombination is facilitated by the ordered arrangement of the products of meiosis in Neurospora ascospores, its entire genome of seven chromosomes has been sequenced. Neurospora was used by Edward Tatum and George Wells Beadle in their experiments for which they won the Nobel Prize in Physiology or Medicine in 1958. Beadle and Tatum exposed N. crassa to x-rays. They observed failures in metabolic pathways caused by errors in specific enzymes; this led them to propose the "one gene, one enzyme" hypothesis that specific genes code for specific proteins.
Their hypothesis was elaborated to enzyme pathways by Norman Horowitz working on Neurospora. As Norman Horowitz reminisced in 2004, "These experiments founded the science of what Beadle and Tatum called'biochemical genetics'. In actuality, they proved to be the opening gun in what became molecular genetics and all developments that have followed from that." In the 24 April 2003 issue of Nature, the genome of N. crassa was reported as sequenced. The genome is about 43 megabases long and includes 10,000 genes. There is a project underway to produce strains containing knockout mutants of every N. crassa gene. In its natural environment, N. crassa lives in tropical and sub-tropical regions. It can be found growing on dead plant matter after fires. Neurospora is used in research around the world, it is important in the elucidation of molecular events involved in circadian rhythms and gene silencing, cell polarity, cell fusion, development, as well as many aspects of cell biology and biochemistry. Sexual fruiting bodies can only be formed.
Like other Ascomycetes, N. crassa has two mating types that, in this case, are symbolized by A and a. There is no evident morphological difference between a mating type strains. Both can form the female reproductive structure. Protoperithecia are formed most in the laboratory when growth occurs on solid synthetic medium with a low source of nitrogen. Nitrogen starvation appears to be necessary for expression of genes involved in sexual development; the protoperithecium consists of an ascogonium, a coiled multicellular hypha, enclosed in a knot-like aggregation of hyphae. A branched system of slender hyphae, called the trichogyne, extends from the tip of the ascogonium projecting beyond the sheathing hyphae into the air; the sexual cycle is initiated. Such contact can be followed by cell fusion leading to one or more nuclei from the fertilizing cell migrating down the trichogyne into the ascogonium. Since both A and a strains have the same sexual structures, neither strain can be regarded as male or female.
However, as a recipient, the protoperithecium of both the A and a strains can be thought of as the female structure, the fertilizing conidium can be thought of as the male participant. The subsequent steps following fusion of A and a haploid cells, have been outlined by Fincham and Day and Wagner and Mitchell. After fusion of the cells, the further fusion of their nuclei is delayed. Instead, a nucleus from the fertilizing cell and a nucleus from the ascogonium become associated and begin to divide synchronously; the products of these nuclear divisions migrate into numerous ascogenous hyphae, which begin to grow out of the ascogonium. Each of these ascogenous hypha bends to form a hook at its tip and the A and a pair of haploid nuclei within the crozier divide synchronously. Next, septa form to divide the crozier into three cells; the central cell in the curve of the hook contains one a nucleus. This binuclear cell is called an "ascus-initial" cell. Next the two uninucleate cells on either side of the first ascus-forming cell fuse with each other to form a binucleate cell that can grow to form a further crozier that can form its own ascus-initial cell.
This process can be repeated multiple times. After formation of the ascus-initial cell, the A and a nucleus fuse with each other to form a diploid nucleus; this nucleus is the only diploid nucleus in the entire life cycle of N. crassa. The diploid nucleus has 14 chromosomes formed from the two fused haploid nuclei that had 7 chromosomes each. Formation of the diploid nucleus is followed by meiosis; the two sequential divisions of meiosis lead to four haploid nuclei, two of the A mating type and two of the a mating type. One further mitotic division leads to four a nucleus in each ascus. Meiosis is an essential part of the life cycle of all sexually reproducing organisms, in its main features, meiosis in N. crassa seems typical of meiosis generally. As the above events are occurring, the mycelial sheath that had enveloped the ascogonium develops as the wall of the perithecium, becomes impregnated with melanin, blackens; the mature perithecium has a flask-shaped structure. A mature perithecium may contain as many as 300 asci, each derived from identical fusion diploid nuclei.
Ordinarily, in nature, when the
Heterothallic species have sexes that reside in different individuals. The term is applied to distinguish heterothallic fungi, which require two compatible partners to produce sexual spores, from homothallic ones, which are capable of sexual reproduction from a single organism. In heterothallic fungi, two different individuals contribute nuclei to form a zygote. Examples of heterothallism are included for Saccharomyces cerevisiae, Aspergillus fumigatus, Aspergillus flavus, Penicillium marneffei and Neurospora crassa; the heterothallic life cycle of N. crassa is given in some detail, since similar life cycles are present in other heterothallic fungi. The yeast Saccharomyces cerevisiae is heterothallic; this means that each yeast cell is of a certain mating type and can only mate with a cell of the other mating type. During vegetative growth that ordinarily occurs when nutrients are abundant, S. cerevisiae reproduces by mitosis as either haploid or diploid cells. However, when starved, diploid cells undergo meiosis to form haploid spores.
Mating occurs when haploid cells of MATa and MATα, come into contact. Ruderfer et al. pointed out that such contacts are frequent between related yeast cells for two reasons. The first is that cells of opposite mating type are present together in the same ascus, the sac that contains the tetrad of cells directly produced by a single meiosis, these cells can mate with each other; the second reason is that haploid cells of one mating type, upon cell division produce cells of the opposite mating type with which they may mate. Katz Ezov et al. presented evidence that in natural S. cerevisiae populations clonal reproduction and a type of “self-fertilization” predominate. Ruderfer et al. analyzed the ancestry of natural S. cerevisiae strains and concluded that outcrossing occurs only about once every 50,000 cell divisions. Thus, although S. cerevisiae is heterothallic, it appears that, in nature, mating is most between related yeast cells. The relative rarity in nature of meiotic events that result from outcrossing suggests that the possible long-term benefits of outcrossing are unlikely to be sufficient for maintaining sex from one generation to the next.
Rather, a short term benefit, such as meiotic recombinational repair of DNA damages caused by stressful conditions such as starvation may be the key to the maintenance of sex in S. cerevisiae. Aspergillus fumigatus, is a heterothallic fungus, it is one of the most common Aspergillus species to cause disease in humans with an immunodeficiency. A. fumigatus, is widespread in nature, is found in soil and decaying organic matter, such as compost heaps, where it plays an essential role in carbon and nitrogen recycling. Colonies of the fungus produce from conidiophores thousands of minute grey-green conidia that become airborne. A. fumigatus possesses a functional sexual reproductive cycle that leads to the production of cleistothecia and ascospores. Although A. fumigatus occurs in areas with different climates and environments, it displays low genetic variation and lack of population genetic differentiation on a global scale. Thus the capability for heterothallic sex is maintained though little genetic diversity is produced.
As in the case of S. cereviae, above, a short-term benefit of meiosis may be the key to the adaptive maintenance of sex in this species. A. flavus is the major producer of carcinogenic aflatoxins in crops worldwide. It is an opportunistic human and animal pathogen, causing aspergillosis in immunocompromised individuals. In 2009, a sexual state of this heterothallic fungus was found to arise when strains of opposite mating type were cultured together under appropriate conditions. Sexuality generates diversity in the aflatoxin gene cluster in A. flavus, suggesting that production of genetic variation may contribute to the maintenance of heterothallism in this species. Henk et al. showed that the genes required for meiosis are present in P. marneffei, that mating and genetic recombination occur in this species. Henk et al. concluded that P. marneffei is sexually reproducing, but recombination in natural populations is most to occur across spatially and genetically limited distances resulting in a clonal population structure.
Sex is maintained in this species though little genetic variability is produced. Sex may be maintained in P. marneffei by a short-term benefit of meiosis, as in S. cerevisiae and A. fumigatus, discussed above. The sexual cycle of N. crassa is heterothallic. Sexual fruiting bodies can only be formed. Like other ascomycetes, N. crassa has two mating types that, in this case, are symbolized by A and a. There is no evident morphological difference between a mating type strains. Both can form the female reproductive structure. Protoperithecia are formed most in the laboratory when growth occurs on solid synthetic medium with a low source of nitrogen. Nitrogen starvation appears to be necessary for expression of genes involved in sexual development; the protoperithecium consists of an ascogonium, a coiled multicellular hypha, enclosed in a knot-like aggregation of hyphae. A branched system of slender hyphae, called the trichogyne, extends from the tip of the ascogonium projecting beyond the sheathing hyphae into the air.
The sexual cycle is initiated. Such contact can be followed by cell fusion leading to one or more nuclei from the fertilizing cell migra
A fungus 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, separate from the other eukaryotic life kingdoms of plants and animals. A characteristic that places fungi in a different kingdom from plants and some protists is chitin in their cell walls. Similar to animals, fungi are heterotrophs. Fungi do not photosynthesize. Growth is their means of mobility, except for spores, which may travel through the water. Fungi are the principal decomposers in ecological systems; these and other differences place fungi in a single group of related organisms, named the Eumycota, which share a common ancestor, an interpretation, strongly supported by molecular phylogenetics. This fungal group oomycetes; the discipline of biology devoted to the study of fungi is known as mycology. In the past, mycology was regarded as a branch of botany, although it is now known fungi are genetically more related to animals than to plants.
Abundant worldwide, most fungi are inconspicuous because of the small size of their structures, their cryptic lifestyles in soil or on dead matter. Fungi include symbionts of plants, animals, or other fungi and parasites, they may become noticeable when fruiting, either as molds. Fungi perform an essential role in the decomposition of organic matter and have fundamental roles in nutrient cycling and exchange in the environment, they have long been used in the form of mushrooms and truffles. Since the 1940s, fungi have been used for the production of antibiotics, more various enzymes produced by fungi are used industrially and in detergents. Fungi are used as biological pesticides to control weeds, plant diseases and insect pests. Many species produce bioactive compounds called mycotoxins, such as alkaloids and polyketides, that are toxic to animals including humans; the fruiting structures of a few species contain psychotropic compounds and are consumed recreationally or in traditional spiritual ceremonies.
Fungi can break down manufactured materials and buildings, become significant pathogens of humans and other animals. Losses of crops due to fungal diseases or food spoilage can have a large impact on human food supplies and local economies; the fungus kingdom encompasses an enormous diversity of taxa with varied ecologies, life cycle strategies, morphologies ranging from unicellular aquatic chytrids to large mushrooms. However, little is known of the true biodiversity of Kingdom Fungi, estimated at 2.2 million to 3.8 million species. Of these, only about 120,000 have been described, with over 8,000 species known to be detrimental to plants and at least 300 that can be pathogenic to humans. Since the pioneering 18th and 19th century taxonomical works of Carl Linnaeus, Christian Hendrik Persoon, Elias Magnus Fries, fungi have been classified according to their morphology or physiology. Advances in molecular genetics have opened the way for DNA analysis to be incorporated into taxonomy, which has sometimes challenged the historical groupings based on morphology and other traits.
Phylogenetic studies published in the last decade have helped reshape the classification within Kingdom Fungi, divided into one subkingdom, seven phyla, ten subphyla. The English word fungus is directly adopted from the Latin fungus, used in the writings of Horace and Pliny; this in turn is derived from the Greek word sphongos, which refers to the macroscopic structures and morphology of mushrooms and molds. The word mycology is derived from the Greek logos, it denotes the scientific study of fungi. The Latin adjectival form of "mycology" appeared as early as 1796 in a book on the subject by Christiaan Hendrik Persoon; the word appeared in English as early as 1824 in a book by Robert Kaye Greville. In 1836 the English naturalist Miles Joseph Berkeley's publication The English Flora of Sir James Edward Smith, Vol. 5. Refers to mycology as the study of fungi. A group of all the fungi present in a particular area or geographic region is known as mycobiota, e.g. "the mycobiota of Ireland". Before the introduction of molecular methods for phylogenetic analysis, taxonomists considered fungi to be members of the plant kingdom because of similarities in lifestyle: both fungi and plants are immobile, have similarities in general morphology and growth habitat.
Like plants, fungi grow in soil and, in the case of mushrooms, form conspicuous fruit bodies, which sometimes resemble plants such as mosses. The fungi are now considered a separate kingdom, distinct from both plants and animals, from which they appear to have diverged around one billion years ago; some morphological and genetic features are shared with other organisms, while others are unique to the fungi separating them from the other kingdoms: Shared features: With other euka