Taxobox
color = lightblue
name = Fungi
fossil_range = Early Devonian - Recent (but see text)
image_width = 280px
image_caption = Clockwise from top left: "Amanita muscaria", a basidiomycete; "Sarcoscypha coccinea", an ascomycete; black bread mold, a zygomycete; a chytrid; a "Penicillium" conidiophore.
domain=Eukarya
unranked_regnum = Opisthokonta
regnum = Fungi
regnum_authority = (L., 1753) R.T. Moore, 1980 [cite journal | title=Taxonomic proposals for the classification of marine yeasts and other yeast-like fungi including the smuts | year=1980 | journal=Bot. Mar. | volume=23 | pages=371]
subdivision_ranks = Subkingdoms/Phyla
subdivision =:Chytridiomycota:Blastocladiomycota:Neocallimastigomycota:Glomeromycota:Zygomycota
Dikarya (inc. Deuteromycota) :Ascomycota:BasidiomycotaA fungus (pronEng|ˈfʌŋgəs) is a eukaryotic organism that is a member of the kingdom Fungi (pronEng|ˈfʌndʒaɪ). [These are the pronunciations listed first in most dictionaries. See, for example, the [http://www.m-w.com/dictionary/fungus Merriam-Webster Online entry] Alternative pronunciations for "fungi" include /ˈfʌŋgaɪ/, /ˈfʌndʒi/, and /ˈfʌŋgi/. "Funguses" (/ˈfʌŋgəsəz/) is an alternative plural form.] The fungi are heterotrophic organisms possessing a chitinous cell wall. The majority of species grow as multicellular filaments called hyphae forming a mycelium; some fungal species also grow as single cells. Sexual and asexual reproduction of the fungi is commonly via spores, often produced on specialized structures or in fruiting bodies. Some species have lost the ability to form specialized reproductive structures, and propagate solely by vegetative growth. Yeasts, molds, and mushrooms are examples of fungi. The fungi are a monophyletic group that is phylogenetically clearly distinct from the morphologically similar slime molds (myxomycetes) and water molds (oomycetes). The fungi are more closely related to animals than plants, yet the discipline of biology devoted to the study of fungi, known as mycology, often falls under a branch of botany.
Occurring worldwide, most fungi are largely invisible to the naked eye, living for the most part in soil, dead matter, and as symbionts of plants, animals, or other fungi. They perform an essential role in all ecosystems in decomposing organic matter and are indispensable in nutrient cycling and exchange. Some fungi become noticeable when fruiting, either as mushrooms or molds. Many fungal species have long been used as a direct source of food, such as mushrooms and truffles and in fermentation of various food products, such as wine, beer, and soy sauce. More recently, fungi are being used as sources for antibiotics used in medicine and various enzymes, such as cellulases, pectinases, and proteases, important for industrial use or as active ingredients of detergents. Many fungi produce bioactive compounds called mycotoxins, such as alkaloids and polyketides that are toxic to animals including humans. Some fungi are used recreationally or in traditional ceremonies as a source of psychotropic compounds. Several species of the fungi are significant pathogens of humans and other animals, and losses due to diseases of crops (e.g., rice blast disease) or food spoilage caused by fungi can have a large impact on human food supply and local economies.
Etymology and definition
The English word "fungus" is directly adopted from the Latin "fungus", meaning "mushroom", used in Horace and Pliny. [cite book|last=Simpson|first=D.P.|title= Cassell's Latin Dictionary|publisher=Cassell Ltd.|date=1979 |edition=5|location=London|pages= 883|id = ISBN 0-304-52257-0] This in turn is derived from the Greek word "sphongos"/σφογγος ("sponge"), referring to the macroscopic structures and morphology of some mushrooms and molds and also used in other languages (e.g., the German "Schwamm" ("sponge") or "Schwammerl" for some types of mushroom).
Diversity
Fungi have a worldwide distribution, and grow in a wide range of habitats, including deserts. Most fungi grow in terrestrial environments, but several species occur only in aquatic habitats. Fungi along with bacteria are the primary decomposers of organic matter in most if not all terrestrial ecosystems worldwide. Based on observations of the ratio of the number of fungal species to the number of plant species in some environments, the fungal kingdom has been estimated to contain about 1.5 million species. [cite journal|author=Hawksworth DL|year= 2006|title=The fungal dimension of biodiversity: magnitude, significance, and conservation|journal=Mycol. Res.|volume=95|pages=641–655] Around 70,000 fungal species have been formally described by taxonomists, but the true dimension of fungal diversity is still unknown. ][cite journal|author=Mueller GM, Schmit JP|year= 2006|title=Fungal biodiversity: what do we know? What can we predict?|journal=Biodivers Conserv|volume=16|pages=1–5|doi=10.1007/s10531-006-9117-7] Most fungi grow as thread-like filaments called hyphae, which form a mycelium, while others grow as single cells. ]
accessdate = 2007-04-06| author = Meredith Blackwell| coauthors = Rytas Vilgalys, and John W. Taylor| date = 2005-02-14] Until recently many fungal species were described based mainly on morphological characteristics, such as the size and shape of spores or fruiting structures, and biological species concepts; the application of molecular tools, such as DNA sequencing, to study fungal diversity has greatly enhanced the resolution and added robustness to estimates of diversity within various taxonomic groups.[cite journal | author=Hibbett, D.S., "et al." | year=2007 | title=A higher level phylogenetic classification of the "Fungi"| journal=Mycol. Res. | volume=111|issue=5 | pages=509–547 | doi=10.1016/j.mycres.2007.03.004] ]Importance for human use
Human use of fungi for food preparation or preservation and other purposes is extensive and has a long history: yeasts are required for fermentation of beer, wine [ [http://winemaking.jackkeller.net/strains.asp Strains of wine yeast] ] and bread, some other fungal species are used in the production of soy sauce and tempeh. Mushroom farming and mushroom gathering are large industries in many countries. Many fungi are producers of antibiotics, including β-lactam antibiotics such as penicillin and cephalosporin.[cite journal|author=Demain AL.|year= 1991|title=Production of beta-lactam antibiotics and its regulation|journal=Proc Natl Sci Counc Repub China B.|volume=15|pages=251–265|pmid=1815263] Widespread use of these antibiotics for the treatment of bacterial diseases, such as tuberculosis, syphilis, leprosy, and many others began in the early 20th century and continues to play a major part in anti-bacterial chemotherapy. The study of the historical uses and sociological impact of fungi is known as ethnomycology. ]Cultured foods
Baker's yeast or "Saccharomyces cerevisiae", a single-cell fungus, is used in the baking of bread and other wheat-based products, such as pizza and dumplings. [cite book |title=Handbook of Cereal Science and Technology |last=Kulp |first=Karel |year=2000 |publisher=CRC Press |isbn=0824782941 ] Several yeast species of the genus Saccharomyces are also used in the production of alcoholic beverages through fermentation.[cite journal|author=Piskur J, Rozpedowska E, Polakova S, Merico A, Compagno C.|year= 2006|title=How did Saccharomyces evolve to become a good brewer?|journal=Trends Genet.|volume=22|pages=183–186|pmid=16499989|doi=10.1016/j.tig.2006.02.002] Mycelial fungi, such as the shoyu koji mold ("Aspergillus oryzae"), are used in the brewing of Shoyu (soy sauce) and preparation of tempeh.][cite journal|author=Kitamoto N, Yoshino S, Ohmiya K, Tsukagoshi N.|year= 1999|title=Sequence analysis, overexpression, and antisense inhibition of a beta-xylosidase gene, xylA, from Aspergillus oryzae KBN616|journal=Appl. Env. Microbiol.|volume=65|pages=20–24|pmid=9872754] Quorn is a high-protein product made from the mold, "Fusarium venenatum", and is used in vegetarian cooking.]Other human uses
Fungi are also used extensively to produce industrial chemicals like lactic acid, antibiotics and even to make stonewashed jeans. [cite web|url=http://www.nysaes.cornell.edu/ent/biocontrol/pathogens/trichoderma.html|title=Trichoderma spp., including T. harzianum, T. viride, T. koningii, T. hamatum and other spp. Deuteromycetes, Moniliales (asexual classification system)|accessdate=2007-07-10|work=Biological Control: A Guide to Natural Enemies in North America] Several fungal species are ingested for their psychedelic properties, both recreationally and religiously (see main article, "Psilocybin mushrooms").
Mycotoxins
Many fungi produce compounds with biological activity. Several of these compounds are toxic and are therefore called mycotoxins, referring to their fungal origin and toxic activity. Of particular relevance to humans are those mycotoxins that are produced by moulds causing food spoilage and poisonous mushrooms (see below). Particularly infamous are the aflatoxins, which are insidious liver toxins and highly carcinogenic metabolites produced by "Aspergillus" species often growing in or on grains and nuts consumed by humans, and the lethal amatoxins produced by mushrooms of the genus "Amanita". Other notable mycotoxins include ochratoxins, patulin, ergot alkaloids, and trichothecenes and fumonisins, all of which have significant impact on human food supplies or animal livestock. [cite journal|author=van Egmond HP, Schothorst RC, Jonker MA|year= 2007|title=Regulations relating to mycotoxins in food: perspectives in a global and European context|journal=Anal Bioanal Chem.|volume=389|pages=147–157|pmid=17508207|doi=10.1007/s00216-007-1317-9] ]Mycotoxins belong to the group of secondary metabolites (or natural products). Originally, this group of compounds had been thought to be mere byproducts of primary metabolism, hence the name "secondary" metabolites. However, recent research has shown the existence of biochemical pathways solely for the purpose of producing mycotoxins and other natural products in fungi. [cite journal|author=Keller NP, Turner G, Bennett JW|year= 2005|title=Fungal secondary metabolism - from biochemistry to genomics|journal=Nat Rev Microbiol.|volume=3|pages=937–497|pmid=16322742|doi=10.1038/nrmicro1286] Mycotoxins provide a number of fitness benefits to the fungi that produce them in terms of physiological adaptation, competition with other microbes and fungi, and protection from fungivory. ][cite journal|author=Demain AL, Fang A|year= 2000|title=The natural functions of secondary metabolites|journal=Adv Biochem Eng Biotechnol.|volume=69|pages=1–39|pmid=11036689] ][cite journal|author=Rohlfs M, Albert M, Keller NP, Kempken F|year= 2007|title=Secondary chemicals protect mould from fungivory|journal=Biol Lett.|volume=3|pages=523–525|pmid=17686752|doi=10.1098/rsbl.2007.0338] These fitness benefits and the existence of dedicated biosynthetic pathways for mycotoxin production suggest that the mycotoxins are important for fungal persistence and survival.]Edible and poisonous fungi
Some of the best known types of fungi are the edible and the poisonous mushrooms. Many species are commercially raised, but others must be harvested from the wild. "Agaricus bisporus", sold as button mushrooms when small or Portobello mushrooms when larger, are the most commonly eaten species, used in salads, soups, and many other dishes. Many Asian fungi are commercially grown and have gained in popularity in the West. They are often available fresh in grocery stores and markets, including straw mushrooms ("Volvariella volvacea"), oyster mushrooms ("Pleurotus ostreatus"), shiitakes ("Lentinula edodes"), and enokitake ("Flammulina" spp.).
There are many more mushroom species that are harvested from the wild for personal consumption or commercial sale. Milk mushrooms, morels, chanterelles, truffles, black trumpets, and "porcini" mushrooms ("Boletus edulis") (also known as king boletes) all demand a high price on the market. They are often used in gourmet dishes.
For certain types of cheeses, it is also a common practice to inoculate milk curds with fungal spores to foment the growth of specific species of mold that impart a unique flavor and texture to the cheese. This accounts for the blue colour in cheeses such as Stilton or Roquefort which is created using "Penicillium roqueforti" spores. [ [http://whatscookingamerica.net/Q-A/CheeseMold.htm Questions & Answers - Mold on Cheese] whatscookingamerica.net. Retrieved 2007-04-06.] Molds used in cheese production are usually non-toxic and are thus safe for human consumption; however, mycotoxins (e.g., aflatoxins, roquefortine C, patulin, or others) may accumulate due to fungal spoilage during cheese ripening or storage.[cite journal|author=Erdogan A, Gurses M, Sert S.|year= 2004|title=Isolation of moulds capable of producing mycotoxins from blue mouldy Tulum cheeses produced in Turkey|journal=Int J Food Microbiol.|volume=85|pages=83–85|pmid=12810273|doi=10.1016/S0168-1605(02)00485-3] ]Many mushroom species are toxic to humans, with toxicities ranging from slight digestive problems or allergic reactions as well as hallucinations to severe organ failures and death. Some of the most deadly mushrooms belong to the genera "Inocybe", "Cortinarius", and most infamously, "Amanita". The latter genus includes the destroying angel "(A. virosa)" and the death cap "(A. phalloides)", the most common cause of deadly mushroom poisoning. [ [http://www.npr.org/templates/story/story.php?storyId=7251327 On the Trail of the Death Cap Mushroom] Richard Harris, www.npr.org, 2007-02-08. Retrieved 2007-04-06.] The false morel ("Gyromitra esculenta") is considered a delicacy by some when cooked, yet can be highly toxic when eaten raw. [cite journal|author=Leathem AM, Dorran TJ|year=2007|title=Poisoning due to raw Gyromitra esculenta (false morels) west of the Rockies|journal=CJEM|volume=9|pages=127–130|pmid=17391587] "Tricholoma equestre" was considered edible until being implicated in some serious poisonings causing rhabdomyolysis. ][cite journal|author=Karlson-Stiber C, Persson H|year=2003|title=Cytotoxic fungi--an overview|journal=Toxicon.|volume=42|pages=339–349|pmid=14505933|doi=10.1016/S0041-0101(03)00238-1] ]Fly agaric mushrooms ("A. muscaria") also cause occasional poisonings, mostly as a result of ingestion for use as a recreational drug for its hallucinogenic properties. Historically Fly agaric was used by Celtic Druids in Northern Europe and the Koryak people of north-eastern Siberia for religious or shamanic purposes. [ [http://www.treesforlife.org.uk/forest/mythfolk/flyagaric.html Mythology and Folklore of Fly Agaric] Paul Kendall, Trees for Life. Retrieved 2007-04-06.] It is difficult to identify a safe mushroom without proper training and knowledge, thus it is often advised to assume that a mushroom in the wild is poisonous and not to consume it.
Fungi in the biological control of pests
In agricultural settings, fungi that actively compete for nutrients and space with, and eventually prevail over, pathogenic microorganisms, such as bacteria or other fungi, via the competitive exclusion principle,[cite journal|author=López-Gómez J, Molina-Meyer M|year= 2006|title=The competitive exclusion principle versus biodiversity through competitive segregation and further adaptation to spatial heterogeneities|journal=Theor Popul Biol.|volume=69|pages=94–109|pmid=16223517|doi=10.1016/j.tpb.2005.08.004] or are parasites of these pathogens, may be beneficial agents for human use. For example, some fungi may be used to suppress growth or eliminate harmful plant pathogens, such as insects, mites, weeds, nematodes and other fungi that cause diseases of important crop plants. [ [http://www.ars.usda.gov/is/AR/archive/jul98/fung0798.htm Setting the Stage To Screen Biocontrol Fungi] Hank Becker, July 1998. Retrieved 2007-04-06.] This has generated strong interest in the use and practical application of these fungi for the biological control of these agricultural pests. Entomopathogenic fungi can be used as biopesticides, as they actively kill insects. [ [http://www.uvminnovations.com/graphics/microfactory.pdf WHEY-BASED FUNGAL MICROFACTORY TECHNOLOGY FOR ENHANCED BIOLOGICAL PEST MANAGEMENT USING FUNGI] Todd. S. Keiller, Technology Transfer, University of Vermont. Retrieved 2007-04-06.] Examples of fungi that have been used as biological insecticides are "Beauveria bassiana", "Metarhizium anisopliae", "Hirsutella" spp, "Paecilomyces" spp, and "Verticillium lecanii".][cite journal|author=Deshpande MV.|year= 1999|title=Mycopesticide production by fermentation: potential and challenges|journal=Crit Rev Microbiol. |volume=25|pages=229–243|pmid=10524330|doi=10.1080/10408419991299220] ][cite journal|author=Thomas MB, Read AF.|year=2007|title=Can fungal biopesticides control malaria?|journal=Nat Rev Microbiol.|volume=5|pages=377–383|pmid=17426726 | doi = 10.1038/nrmicro1638 ] Endophytic fungi of grasses of the genus "Neotyphodium", such as "N. coenophialum" produce alkaloids that are toxic to a range of invertebrate and vertebrate herbivores. These alkaloids protect the infected grass plants from herbivory, but some endophyte alkaloids can cause poisoning of grazing animals, such as cattle and sheep. ][cite journal|author=Bush LP, Wilkinson HH, Schardl CL.|year=1997|title=Bioprotective Alkaloids of Grass-Fungal Endophyte Symbioses|journal=Plant Physiol.|volume=114|pages=1–7|pmid=12223685] Infection of grass cultivars of turf or forage grasses with isolates of the grass endophytes that produce only specific alkaloids to improve grass hardiness and resistance to herbivores such as insects, while being non-toxic to livestock, is being used in grass breeding programs.][cite journal|author=Bouton JH, Latch GCM, Hill NS, Hoveland CS, McCannc MA, Watson RH, Parish JA, Hawkins LL, Thompson FN|year=2002|title=Use of nonergot alkaloid-producing endophytes for alleviating tall fescue toxicosis in sheep|journal=Agron. J.|volume=94|pages=567–574|id=http://agron.scijournals.org/cgi/content/full/94/3/567] ]Bioremediation
Certain fungi, in particular 'white rot' fungi, can degrade insecticides, herbicides, pentachlorophenol, creosote, coal tars, and heavy fuels and turn them into carbon dioxide, water, and basic elements. [Douglas, M.S. (1995). [http://stinet.dtic.mil/oai/oai?verb=getRecord&metadataPrefix=html&identifier=ADA307994 Bioremediation of Contaminated Soils Using the White Rot Fungus Phanerochaete Chrysosporium] . DTIC.] Research has recently discovered that fungi can be used to lock uranium into mineral form. [BBC. (2008). [http://news.bbc.co.uk/2/hi/uk_news/scotland/tayside_and_central/7384500.stm Fungi to fight 'toxic war zones'] ]
Ecology
Although often inconspicuous, fungi occur in every environment on Earth and play very important roles in most ecosystems. Along with bacteria, fungi are the major decomposers in most terrestrial (and some aquatic) ecosystems, and therefore play a critical role in biogeochemical cycles and in many food webs. As decomposers, they play an indispensable role in nutrient cycling, especially as saprotrophs and symbionts, degrading organic matter to inorganic molecules, which can then re-enter anabolic metabolic pathways in plants or other organisms.[cite journal|author=Lindahl BD, Ihrmark K, Boberg J, Trumbore SE, Högberg P, Stenlid J, Finlay RD|year= 2007|title=Spatial separation of litter decomposition and mycorrhizal nitrogen uptake in a boreal forest|journal=New Phytol.|volume=173|pages=611–620|pmid=17244056|doi=10.1111/j.1469-8137.2006.01936.x] ][cite journal|author=Barea JM, Pozo MJ, Azcón R, Azcón-Aguilar C|year= 2005|title=Microbial co-operation in the rhizosphere|journal=J. Exp. Bot.|volume=56|pages=1761–1778|pmid=15911555|doi=10.1093/jxb/eri197] ]ymbiosis
Many fungi have important symbiotic relationships with organisms from most if not all Kingdoms.[cite journal|author=Aanen DK.|year= 2006|title=As you reap, so shall you sow: coupling of harvesting and inoculating stabilizes the mutualism between termites and fungi|journal=Biol Lett.|volume=2|pages=209–212|pmid=17148364|doi=10.1098/rsbl.2005.0424] ][cite journal|author=Nikoh N, Fukatsu T.|year= 2000|title=Interkingdom host jumping underground: phylogenetic analysis of entomoparasitic fungi of the genus Cordyceps|journal=Mol Biol Evol.|volume=17|pages=2629–2638|pmid=10742053] ][cite journal|author=Perotto S, Bonfante P.|year=1997|title=Bacterial associations with mycorrhizal fungi: close and distant friends in the rhizosphere|journal=Trends Microbiol.|volume=5|pages=496–501|pmid=9447662|doi=10.1016/S0966-842X(97)01154-2] These interactions can be mutualistic or antagonistic in nature, or in case of commensal fungi are of no apparent benefit or detriment to the host. ][cite journal|author=Arnold AE, Mejía LC, Kyllo D, Rojas EI, Maynard Z, Robbins N, Herre EA.|year=2003|title=Fungal endophytes limit pathogen damage in a tropical tree|journal=Proc. Natl. Acad. Sci. USA|volume=100|pages=15649–15654|pmid=14671327|doi=10.1073/pnas.2533483100] ][cite journal|author=Paszkowski U.|year=2006|title=Mutualism and parasitism: the yin and yang of plant symbioses|journal=Curr Opin Plant Biol.|volume=9|pages=364–370|pmid=16713732|doi=10.1016/j.pbi.2006.05.008] ][cite journal|author=Hube B.|year=2004|title=From commensal to pathogen: stage- and tissue-specific gene expression of Candida albicans|journal=Curr Opin Microbiol.|volume=7|pages=336–341|pmid=15288621|doi=10.1016/j.mib.2004.06.003] ]With plants
Mycorrhizal symbiosis between plants and fungi is one of the most well-known plant-fungus associations and is of significant importance for plant growth and persistence in many ecosystems; over 90% of all plant species engage in some kind of mycorrhizal relationship with fungi and are dependent upon this relationship for survival. [cite web | last = Volk | first = Tom | title = Tom Volk's Fungi FAQ|url=http://botit.botany.wisc.edu/toms_fungi/faq.html | accessdate = 2006-09-21] [cite web | last = Wong | first = George | title = Symbiosis: Mycorrhizae and Lichens | url=http://www.botany.hawaii.edu/faculty/wong/BOT135/Lect26.htm | accessdate = 2006-09-21 ] [ [http://southwestfarmpress.com/news/6-10-05-nitrogen-transfer-beneficial-fungi/ Knowledge of nitrogen transfer between plants and beneficial fungi expands] southwestfarmpress.com. 2005-06-10 Retrieved 2007-04-06.] The mycorrhizal symbiosis is ancient, dating to at least 400 million years ago.[cite journal|author=Remy W, Taylor TN, Hass H, Kerp H |year=1994|title= 4-hundred million year old vesicular-arbuscular mycorrhizae|journal= Proc. Natl. Acad. Sci|volume=91|pages=11841–11843|pmid=11607500|doi= 10.1073/pnas.91.25.11841] It often increases the plant's uptake of inorganic compounds, such as nitrate and phosphate from soils having low concentrations of these key plant nutrients.][cite journal|author=van der Heijden MG, Streitwolf-Engel R, Riedl R, Siegrist S, Neudecker A, Ineichen K, Boller T, Wiemken A, Sanders IR|year= 2006|title=The mycorrhizal contribution to plant productivity, plant nutrition and soil structure in experimental grassland|journal=New Phytol.|volume=172|pages=739–752|pmid=17096799 | doi = 10.1111/j.1469-8137.2006.01862.x ] In some mycorrhizal associations, the fungal partners may mediate plant-to-plant transfer of carbohydrates and other nutrients. Such mycorrhizal communities are called "common mycorrhizal networks". ][cite journal|author=Selosse MA, Richard F, He X, Simard SW|year= 2006|title=Mycorrhizal networks: des liaisons dangereuses?|journal=Trends Ecol Evol.|volume=21|pages=621–628|pmid=16843567|doi=10.1016/j.tree.2006.07.003] ]Lichens are formed by a symbiotic relationship between algae or cyanobacteria (referred to in lichens as "photobionts") and fungi (mostly various species of ascomycetes and a few basidiomycetes), in which individual photobiont cells are embedded in a tissue formed by the fungus.[cite book |title=Lichens of North America |last=Brodo |first=Irwin M. |coauthors=Sylvia Duran Sharnoff |year=2001 |publisher=Yale University Press |isbn=0300082495 ] As in mycorrhizas, the photobiont provides sugars and other carbohydrates, while the fungus provides minerals and water. The functions of both symbiotic organisms are so closely intertwined that they function almost as a single organism.]With insects
Many insects also engage in mutualistic relationships with various types of fungi. Several groups of ants cultivate fungi in the order Agaricales as their primary food source, while ambrosia beetles cultivate various species of fungi in the bark of trees that they infest. [ [http://www.botany.hawaii.edu/faculty/wong/BOT135/Lect24.htm Fungi and Insect Symbiosis] www.botany.hawaii.edu. Retrieved 2007-04-06.] Termites on the African Savannah are also known to cultivate fungi. [Pascal Jouquet, Virginie Tavernier, Luc Abbadie and Michel Lepage. "Nests of subterranean fungus-growing termites (Isoptera, Macrotermitinae) as nutrient patches for grasses in savannah ecosystems". African Journal of Ecology. 2005. Vol 43, 191–196]
As pathogens and parasites
However, many fungi are parasites on plants, animals (including humans), and other fungi. Serious fungal pathogens of many cultivated plants causing extensive damage and losses to agriculture and forestry include the rice blast fungus "Magnaporthe oryzae",[cite journal|author=Talbot NJ|year=2003|title=On the trail of a cereal killer: Exploring the biology of Magnaporthe grisea|journal=Annu Rev Microbiol.|volume=57|pages=177–202|pmid=14527276|doi=10.1146/annurev.micro.57.030502.090957] tree pathogens such as "Ophiostoma ulmi" and "Ophiostoma novo-ulmi" causing Dutch elm disease,][cite journal|author=Paoletti M, Buck KW, Brasier CM.|year=2006|title=Selective acquisition of novel mating type and vegetative incompatibility genes via interspecies gene transfer in the globally invading eukaryote Ophiostoma novo-ulmi|journal=Mol Ecol.|volume=15|pages=249–262|pmid=16367844|doi=10.1111/j.1365-294X.2005.02728.x] and "Cryphonectria parasitica" responsible for chestnut blight, ][cite journal|author=Gryzenhout M, Wingfield BD, Wingfield MJ.|year=2006|title=New taxonomic concepts for the important forest pathogen Cryphonectria parasitica and related fungi|journal=FEMS Microbiol Lett.|volume=258|pages=161–172|pmid=16640568|doi=10.1111/j.1574-6968.2006.00170.x] and plant-pathogenic fungi in the genera "Fusarium", "Ustilago", "Alternaria", and "Cochliobolus"; ][cite journal|author=Nielsen K, Heitman J.|year=2007|title=Sex and virulence of human pathogenic fungi|journal=Adv Genet.|volume=57|pages=143–173|pmid=17352904|doi=10.1016/S0065-2660(06)57004-X] ][cite journal|author=Brakhage AA|year=2005|title=Systemic fungal infections caused by Aspergillus species: epidemiology, infection process and virulence determinants|journal=Curr. Drug Targets|volume=6|pages=875–886|pmid=16375671 | doi = 10.2174/138945005774912717 ] "Histoplasma",][cite journal|author=Kauffman CA.|year=2007|title=Histoplasmosis: a clinical and laboratory update|journal=Clin Microbiol Rev.|volume=20|pages=115–132|pmid=17223625|doi=10.1128/CMR.00027-06] and "Pneumocystis". ][cite journal|author=Cushion MT, Smulian AG, Slaven BE, Sesterhenn T, Arnold J, Staben C, Porollo A, Adamczak R, Meller J.|year=2007|title=Transcriptome of Pneumocystis carinii during Fulminate Infection: Carbohydrate Metabolism and the Concept of a Compatible Parasite|journal=PLoS ONE|volume=2|pages=e423|pmid=17487271 | doi = 10.1371/journal.pone.0000423 ] Several pathogenic fungi are also responsible for relatively minor human diseases, such as athlete’s foot and ringworm. Some fungi are predators of nematodes, which they capture using an array of specialized structures, such as constricting rings or adhesive nets. [ [http://www.uoguelph.ca/~gbarron/MISC2003/illustra.htm ILLUSTRATIONS for Predatory Fungi, wood Decay and the Carbon Cycle] www.uoguelph.ca. Retrieved 2007-04-06.] ]Nutrition and possible autotrophy
Growth of fungi as hyphae on or in solid substrates or single cells in aquatic environments is adapted to efficient extraction of nutrients from these environments, because these growth forms have high surface area to volume ratios. These adaptations in morphology are complemented by hydrolytic enzymes secreted into the environment for digestion of large organic molecules, such as polysaccharides, proteins, lipids, and other organic substrates into smaller molecules. [cite journal|author=Pereira JL, Noronha EF, Miller RN, Franco OL.|year= 2007|title=Novel insights in the use of hydrolytic enzymes secreted by fungi with biotechnological potential|journal=Lett Appl Microbiol.|volume=44|pages=573–581|pmid=17576216|doi=10.1111/j.1472-765X.2007.02151.x] ][cite journal|author=Schaller M, Borelli C, Korting HC, Hube B.|year= 2007|title=Hydrolytic enzymes as virulence factors of Candida albicans|journal=Mycoses|volume=48|pages=365–377|pmid=16262871|doi=10.1111/j.1439-0507.2005.01165.x] ][cite journal|author=Farrar JF|year=1985|title=Carbohydrate metabolism in biotrophic plant pathogens|journal=Microbiol Sci.|volume=2|pages=314–317|pmid=3939987] These molecules are then absorbed as nutrients into the fungal cells.]Traditionally, the fungi are considered heterotrophs, organisms that rely solely on carbon fixed by other organisms for metabolism. Fungi have evolved a remarkable metabolic versatility that allows many of them to use a large variety of organic substrates for growth, including simple compounds as nitrate, ammonia, acetate, or ethanol.[cite journal|author=Marzluf GA|year=1981|title=Regulation of nitrogen metabolism and gene expression in fungi|journal=Microbiol Rev.|volume=45|pages=437–461|pmid=6117784] ][cite journal|author=Heynes MJ|year=1994|title=Regulatory circuits of the amdS gene of Aspergillus nidulans|journal=Antonie Van Leeuwenhoek.|volume=65|pages=179–782|pmid=7847883|doi=10.1007/BF00871944] Recent research raises the possibility that some fungi utilize the pigment melanin to extract energy from ionizing radiation, such as gamma radiation for "radiotrophic" growth. ][cite journal|author=Dadachova E, Bryan RA, Huang X, Moadel T, Schweitzer AD, Aisen P, Nosanchuk JD, Casadevall A.|year= 2007|title=Ionizing radiation changes the electronic properties ofmelanin and enhances the growth of melanized fungi|journal=PLoS ONE|volume=2|pages=e457|pmid=17520016|doi=10.1371/journal.pone.0000457] It has been proposed that this process might bear some similarity to photosynthesis in plants, ]Morphology
Microscopic structures
Though fungi are part of the opisthokont clade, all phyla except for the chytrids have lost their posterior flagella. [ [http://mbe.oxfordjournals.org/cgi/content/full/23/1/93 The Protistan Origins of Animals and Fungi] Emma T. Steenkamp, Jane Wright and Sandra L. Baldauf. Molecular Biology and Evolution 2006 23(1):93-106; doi:10.1093/molbev/msj011. Retrieved 2007-04-06.] Fungi are unusual among the eukaryotes in having a cell wall that, besides glucans (e.g., β-1,3-glucan) and other typical components, contains the biopolymer chitin.[cite journal|author=Stevens DA, Ichinomiya M, Koshi Y, Horiuchi H.|year= 2006|title=Escape of Candida from caspofungin inhibition at concentrations above the MIC (paradoxical effect) accomplished by increased cell wall chitin; evidence for beta-1,6-glucan synthesis inhibition by caspofungin|journal=Antimicrob Agents Chemother.|volume=50|pages=3160–3161.|pmid=16940118|doi=10.1128/AAC.00563-06] ]Many fungi grow as thread-like filamentous microscopic structures called hyphae, and an assemblage of intertwined and interconnected hyphae is called a mycelium. [cite book|author=Alexopoulos CJ, Mims CW, Blackwell M| title=Introductory Mycology | year=1996 | publisher=John Wiley and Sons | isbn=0471522295] Hyphae can be septate, i.e., divided into hyphal compartments separated by a "septum", each compartment containing one or more nuclei or can be coenocytic, i.e., lacking hyphal compartmentalization. However, septa have pores, such as the doliporus in the basidiomycetes that allow cytoplasm, organelles, and sometimes nuclei to pass through.]Macroscopic structures
Fungal mycelia can become visible macroscopically, for example, as concentric rings on various surfaces, such as damp walls, and on other substrates, such as spoilt food (see figure), and are commonly and generically called "mould" (American spelling, "mold"); fungal mycelia grown on solid agar media in laboratory petri dishes are usually referred to as colonies, with many species exhibiting characteristic macroscopic growth morphologies and colours, due to spores or pigmentation.
Specialized fungal structures important in sexual reproduction are the apothecia, perithecia, and cleistothecia in the ascomycetes, and the fruiting bodies of the basidiomycetes, and a few ascomycetes. These reproductive structures can sometimes grow very large, and are well known as mushrooms.
Morphological and physiological features for substrate penetration
Fungal hyphae are specifically adapted to growth on solid surfaces and within substrates, and can exert astoundingly large penetrative mechanical forces. The plant pathogen, "Magnaporthe grisea", forms a structure called an appressorium specifically designed for penetration of plant tissues, and the pressure generated by the appressorium, which is directed against the plant epidermis can exceed 8 MPa (80 bars). [cite journal|author=Howard RJ, Ferrari MA, Roach DH, Money NP|year=1991|title=Penetration of hard substrates by a fungus employing enormous turgor pressures|journal=Proc Natl Acad Sci U S A.|volume=88|pages=11281–11284|pmid=1837147|doi=10.1073/pnas.88.24.11281] The generation of these mechanical pressures is the result of an interplay between physiological processes to increase intracellular turgor by production of osmolytes such as glycerol, and the morphology of the appressorium. ][cite journal|author=Wang ZY, Jenkinson JM, Holcombe LJ, Soanes DM, Veneault-Fourrey C, Bhambra GK, Talbot NJ|year=2005|title=The molecular biology of appressorium turgor generation by the rice blast fungus Magnaporthe grisea|journal=Biochem Soc Trans.|volume=33|pages=384–388|pmid=15787612|doi=10.1042/BST0330384] ]Reproduction
Reproduction of fungi is complex, reflecting the heterogeneity in lifestyles and genetic make up within this group of organisms.
Asexual reproduction
Asexual reproduction via vegetative spores or through mycelial fragmentation is common in many fungal species and allows more rapid dispersal than sexual reproduction. In the case of the "Fungi imperfecti" or Deuteromycota, which lack a sexual cycle, it is the only means of propagation. Asexual spores, upon germination, may found a population that is clonal to the population from which the spore originated, and thus colonize new environments.
exual reproduction
Sexual reproduction with meiosis exists in all fungal phyla, except the Deuteromycota. It differs in many aspects from sexual reproduction in animals or plants. Many differences also exist between fungal groups and have been used to discriminate fungal clades and species based on morphological differences in sexual structures and reproductive strategies. Experimental crosses between fungal isolates can also be used to identify species based on biological species concepts. The major fungal clades have initially been delineated based on the morphology of their sexual structures and spores; for example, the spore-containing structures, asci and basidia, can be used in the identification of ascomycetes and basidiomycetes, respectively. Many fungal species have elaborate vegetative incompatibility systems that allow mating only between individuals of opposite mating type, while others can mate and sexually reproduce with any other individual or itself. Species of the former mating system are called heterothallic, and of the latter homothallic. [cite journal|author=Metzenberg RL, Glass NL.|year= 1990|title=Mating type and mating strategies in Neurospora|journal=Bioessays|volume=12|pages=53–59|pmid=2140508|doi=10.1002/bies.950120202 ] ]Most fungi have both a haploid and diploid stage in their life cycles. In all sexually reproducing fungi, compatible individuals combine by cell fusion of vegetative hyphae by anastomosis, required for the initiation of the sexual cycle. Ascomycetes and basidiomycetes go through a dikaryotic stage, in which the nuclei inherited from the two parents do not fuse immediately after cell fusion, but remain separate in the hyphal cells (see heterokaryosis).
In ascomycetes, dikaryotic hyphae of the hymenium form a characteristic "hook" at the hyphal septum. During cell division formation of the hook ensures proper distribution of the newly divided nuclei into the apical and basal hyphal compartments. An ascus (plural asci) is then formed, in which karyogamy (nuclear fusion) occurs. These asci are embedded in an ascocarp, or fruiting body, of the fungus. Karyogamy in the asci is followed immediately by meiosis and the production of ascospores. The ascospores are disseminated and germinate and may form a new haploid mycelium.
Sexual reproduction in basidiomycetes is similar to that of the ascomycetes. Compatible haploid hyphae fuse to produce a dikaryotic mycelium. However, the dikaryotic phase is more extensive in the basidiomycetes, in many cases also present in the vegetatively growing mycelium. A specialized anatomical structure, called a "clamp connection", is formed at each hyphal septum. As with the structurally similar hook in the ascomycetes, formation of the clamp connection in the basidiomycetes is required for controlled transfer of nuclei during cell division, to maintain the dikaryotic stage with two genetically different nuclei in each hyphal compartment.
In zygomycetes, haploid hyphae of two individuals fuse, forming a zygote, which develops into a zygospore. When the zygospore germinates, it quickly undergoes meiosis, generating new haploid hyphae, which in turn may form asexual sporangiospores. These sporangiospores are means of rapid dispersal of the fungus and germinate into new genetically identical haploid fungal colonies, able to mate and undergo another sexual cycle followed by the generation of new zygospores, thus completing the lifecycle.
pore dispersal
Both asexual and sexual spores or sporangiospores of many fungal species are actively dispersed by forcible ejection from their reproductive structures. This ejection ensures exit of the spores from the reproductive structures as well as travelling through the air over long distances. Many fungi thereby possess specialized mechanical and physiological mechanisms as well as spore-surface structures, such as hydrophobins, for spore ejection. These mechanisms include, for example, forcible discharge of ascospores enabled by the structure of the ascus and accumulation of osmolytes in the fluids of the ascus that lead to explosive discharge of the ascospores into the air. [cite journal|author=Trail F.|year= 2007|title=Fungal cannons: explosive spore discharge in the Ascomycota|journal=FEMS Microbiol Lett.|volume=276|pages=12–18|pmid=17784861|doi=10.1111/j.1574-6968.2007.00900.x] The forcible discharge of single spores termed "ballistospores" involves formation of a small drop of water (Buller's drop), which upon contact with the spore leads to its projectile release with an initial acceleration of more than 10,000 g. ][cite journal|author=Pringle A, Patek SN, Fischer M, Stolze J, Money NP.|year= 2005|title=The captured launch of a ballistospore|journal=Mycologia|volume=97|pages=866–871|pmid=16457355|doi=10.3852/mycologia.97.4.866] Other fungi rely on alternative mechanisms for spore release, such as external mechanical forces, exemplified by puffballs. Attracting insects, such as flies, to fruiting structures, by virtue of their having lively colours and a putrid odour, for dispersal of fungal spores is yet another strategy, most prominently used by the stinkhorns.]Other sexual processes
Besides regular sexual reproduction with meiosis, some fungal species may exchange genetic material via parasexual processes, initiated by anastomosis between hyphae and plasmogamy of fungal cells. The frequency and relative importance of parasexual events is unclear and may be lower than other sexual processes. However, it is known to play a role in intraspecific hybridization [cite journal|author=Furlaneto MC, Pizzirani-Kleiner AA.|year= 1992|title=Intraspecific hybridisation of Trichoderma pseudokoningii by anastomosis and by protoplast fusion|journal= FEMS Microbiol Lett.|volume=69|pages=191–195|pmid=1537549|doi=10.1111/j.1574-6968.1992.tb05150.x] and is also likely required for hybridization between fungal species, which has been associated with major events in fungal evolution. ][cite journal|author=Schardl CL, Craven KD.|year= 2003|title=Interspecific hybridization in plant-associated fungi and oomycetes: a review|journal= Mol. Ecol.|volume=12|pages=2861–2873|pmid=14629368|doi=10.1046/j.1365-294X.2003.01965.x] ]Phylogeny and classification
For a long time taxonomists considered fungi to be members of the Plant Kingdom. This early classification was based mainly on similarities in lifestyle: both fungi and plant are mainly sessile, have similarities in general morphology and growth habitat (like plants, fungi often grow in soil, in the case of mushrooms forming conspicuous fruiting bodies, which sometimes bear resemblance to plants such as mosses). Moreover, both groups possess a cell wall, which is absent in the Animal Kingdom. However, the fungi are now considered a separate kingdom, distinct from both plants and animals, from which they appear to have diverged approximately one billion years ago.[cite journal|author=Bruns T.|year= 2006|title=Evolutionary biology: a kingdom revised|journal=Nature|volume=443|pages=758–761|pmid=17051197 | doi = 10.1038/443758a] Many studies have identified several distinct morphological, biochemical, and genetic features in the Fungi, clearly delineating this group from the other kingdoms. For these reasons, the fungi are placed in their own kingdom.]Physiological and morphological traits
Similar to animals and unlike most plants, fungi lack the capacity to synthesize organic carbon by chlorophyll-based photosynthesis; whereas plants store the reduced carbon as starch, fungi, like animals and some bacteria, use glycogen [cite journal|author=Bowman SM, Free SJ.|year= 2006|title=The structure and synthesis of the fungal cell wall|journal=Bioessays|volume=28|pages=799–808|pmid=16927300|doi=10.1002/bies.20441] also present in some animals, such as the insects and crustaceans, while the plant cell wall consists chiefly of the carbohydrate cellulose. The defining and unique characteristics of fungal cells include growth as hyphae, which are microscopic filaments of between 2-10 microns in diameter and up to several centimetres in length, and which combined form the fungal mycelium. Some fungi, such as yeasts, grow as single ovoid cells, similar to unicellular algae and the protists.]Unlike many plants, most fungi lack an efficient vascular system, such as xylem or phloem for long-distance transport of water and nutrients; as an example for convergent evolution, some fungi, such as "Armillaria", form rhizomorphs or mycelial cords,[cite journal|author= Mihail JD, Bruhn JN.|year= 2005|title=Foraging behaviour of Armillaria rhizomorph systems|journal=Mycol. Res.|volume=109|pages=1195–1207|pmid=16279413|doi=10.1017/S0953756205003606] resembling and functionally related to, but morphologically distinct from, plant roots.]Some characteristics shared between plants and fungi include the presence of vacuoles in the cell,[cite journal|author=Shoji JY, Arioka M, Kitamoto K|year= 2006|title=Possible involvement of pleiomorphic vacuolar networks in nutrient recycling in filamentous fungi|journal=Autophagy. |volume=2|pages=226–227|pmid=16874107] and a similar pathway in the biosynthesis of terpenes using mevalonic acid and pyrophosphate as biochemical precursors; plants however use an additional terpene biosynthesis pathway in the chloroplasts that is apparently absent in fungi.][cite journal|author=Wu S, Schalk M, Clark A, Miles RB, Coates R, Chappell J.|year= 2007|title=Redirection of cytosolic or plastidic isoprenoid precursors elevates terpene production in plants|journal=Nat Biotechnol.|volume=24|pages=1441–7|pmid=17057703|doi=10.1038/nbt1251] Ancestral traits shared among members of the fungi include chitinous cell walls and heterotrophy by absorption.][cite journal|author=Xu H, Andi B, Qian J, West AH, Cook PF|year= 2006|title=The alpha-aminoadipate pathway for lysine biosynthesis in fungi|journal=Cell Biochem Biophys.|volume=46|pages=43–64|pmid=16943623|doi=10.1385/CBB:46:1:43] ]Similar to plants, fungi produce a plethora of secondary metabolites functioning as defensive compounds or for niche adaptation; however, biochemical pathways for the synthesis of similar or even identical compounds often differ markedly between fungi and plants. [cite journal|author=Tudzynski B.|year= 2005|title=Gibberellin biosynthesis in fungi: genes, enzymes, evolution, and impact on biotechnology|journal=Appl Microbiol Biotechnol.|volume=66|pages=597–611|pmid=15578178|doi=10.1007/s00253-004-1805-1] ][cite journal|author=Siewers V, Smedsgaard J, Tudzynski P.|year= 2004|title=The P450 monooxygenase BcABA1 is essential for abscisic acid biosynthesis in Botrytis cinerea|journal=Appl Environ. Microbiol.|volume=70|pages=3868–3876|pmid=15240257 | doi = 10.1128/AEM.70.7.3868-3876.2004 ] ]Evolutionary history
The first organisms having features typical of fungi date to Ma|1200, the Proterozoic.[cite journal]
author = Butterfield, N.J.
year = 2005
title = Probable Proterozoic fungi
journal = Paleobiology
volume = 31
issue = 1
pages = 165–182
doi = ...
doi_brokendate = 2008-06-24] However, fungal fossils do not become common and uncontroversial until the early Devonian, when they are abundant in the Rhynie chert.Even though traditionally included in many botany curricula and textbooks, fungi are now thought to be more closely related to animals than to plants and are placed with the animals in the monophyletic group of opisthokonts.[cite book|author= P. Sitte, H. Ziegler, F. Ehrendorfer|title=Strasburger Lehrbuch der Botanik (Textbook of Botany)|year=1991|edition=33 ed|publisher=Urban & Fischer| isbn=3437204475] For much of the Paleozoic Era, the fungi appear to have been aquatic, and consisted of organisms similar to the extant Chytrids in having flagellum-bearing spores.][cite journal|author=James TY et al|year= 2006|title=Reconstructing the early evolution of Fungi using a six-gene phylogeny|journal=Nature|volume=443|pages=818–822|pmid=17051209 | doi = 10.1038/nature05110] The early fossil record of the fungi is fragmentary, to say the least. The fungi probably colonized the land during the Cambrian, long before land plants.][cite journal]
author = Brundrett, M.C.
year = 2002
title = Coevolution of roots and mycorrhizas of land plants
journal = New Phytologist
volume = 154
issue = 2
pages = 275–304
doi = 10.1046/j.1469-8137.2002.00397.x] All modern classes of fungi were present in the Late Carboniferous (Pennsylvanian Epoch). [Blackwell, Meredith, Vilgalys, Rytas, James, Timothy Y., and Taylor, John W. 2008. Fungi. Eumycota: mushrooms, sac fungi, yeast, molds, rusts, smuts, etc.. Version 21 February 2008. http://tolweb.org/Fungi/2377/2008.02.21 in The Tree of Life Web Project, http://tolweb.org/ ] For some time after the Permian-Triassic extinction event, a fungal spike, originally thought to be an extraordinary abundance of fungal spores in sediments formed shortly after this event, suggested that they were the dominant life form during this period—nearly 100% of the fossil record available from this period.[Eshet, Y. et al. (1995) Fungal event and palynological record of ecological crisis and recovery across the Permian-Triassic boundary. "Geology", 23, 967-970.] However, the relative proportion of fungal spores relative to spores formed by algal species is difficult to assess, ][cite journal | author = Foster, C.B. | coauthors = Stephenson, M.H.; Marshall, C.; Logan, G.A.; Greenwood, P.F. | year = 2002 | title = A Revision Of Reduviasporonites Wilson 1962: Description, Illustration, Comparison And Biological Affinities | journal = Palynology | volume = 26 | issue = 1 | pages = 35–58 | doi = 10.2113/0260035 | url=http://palynology.geoscienceworld.org/cgi/content/abstract/26/1/35] the spike did not appear world-wide, [ cite journal | title=Permian-Triassic Transition in Spain: A multidisciplinary approach | journal=Palaeogeography, Palaeoclimatology, Palaeoecology | volume=229 | issue=1-2 | date=2005 | pages=1–2 | doi=10.1016/j.palaeo.2005.06.028 | url=http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V6R-4GR8RWF-5&_user=1495569&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000053194&_version=1&_urlVersion=0&_userid=1495569&md5=537a1a5b0a8e04cca2221ecb12afb1e9 | author=López-Gómez, J. and Taylor, E.L. ] ][cite journal | author = Looy, C.V. | coauthors = Twitchett, R.J.; Dilcher, D.L.; Van Konijnenburg-van Cittert, J.H.A.; Visscher, H. | year = 2005 | title = Life in the end-Permian dead zone | journal = Proceedings of the National Academy of Sciences | volume = 162 | issue = 4 | pages = 653–659 | doi = 10.1073/pnas.131218098 | quote = See image 2 | pmid = 11427710] and in many places it did not fall on the Permian-Triassic boundary.][cite journal|author=Ward PD, Botha J, Buick R, De Kock MO, Erwin DH, Garrison GH, Kirschvink JL & Smith R|date=2005|title=Abrupt and Gradual Extinction Among Late Permian Land Vertebrates in the Karoo Basin, South Africa|journal=Science|volume=307|issue=5710|pages=709–714|doi=10.1126/science.1107068] ]Analyses using molecular phylogenetics support a monophyletic origin of the Fungi.
There is no unique generally accepted system at the higher taxonomic levels and there are constant name changes at every level, from species upwards. However, efforts among fungal researchers are now underway to establish and encourage usage of a unified and more consistent nomenclature.
Cladogram
Clade
style= font-size:100%; line-height:100%
label1="Unikonta"
1=clade
1="Amoebozoa"
label2= "Opisthokonta"
2=clade
label1 =
1=clade|label1= |1="Animalia"|2="Choanozoa"
label3= "Fungi"
3=clade
1="Chytridiomycota"
2="Blastocladiomycota"
3="Neocallimastigomycota"
4="Zygomycota"
5="Glomeromycota"
label6= "Dikarya"
6=clade
1="Ascomycota"
2="Basidiomycota"
The taxonomic groups of fungi
The major divisions (phyla) of fungi have been classified based mainly on their sexual reproductive structures. Currently, seven fungal divisions are proposed:
* The Chytridiomycota are commonly known as chytrids. These fungi are ubiquitous with a worldwide distribution; chytrids produce zoospores that are capable of active movement through aqueous phases with a single flagellum. Consequently, some taxonomists had earlier classified them as protists on the basis of the flagellum. Molecular phylogenies, inferred from the rRNA-operon sequences representing the 18S, 28S, and 5.8S ribosomal subunits, suggest that the Chytrids are a basal fungal group divergent from the other fungal divisions, consisting of four major clades with some evidence for paraphyly or possibly polyphyly. [cite journal|author=James TY, Letcher PM, Longcore JE, Mozley-Standridge SE, Porter D, Powell MJ, Griffith GW, Vilgalys R.|year=2006|title=A molecular phylogeny of the flagellated fungi (Chytridiomycota) and description of a new phylum (Blastocladiomycota)|journal=Mycologia|volume=98|pages=860–871|pmid=17486963|doi=10.3852/mycologia.98.6.860] ]
* The Blastocladiomycota were previously considered a taxonomic clade within the Chytridiomycota. Recent molecular data and ultrastructural characteristics, however, place the Blastocladiomycota as a sister clade to the Zygomycota, Glomeromycota, and Dikarya (Ascomycota and Basiomycota). The blastocladiomycetes are fungi that are saprotrophs and parasites of all eukaryotic groups and undergo sporic meiosis unlike their close relatives, the chytrids, which mostly exhibit zygotic meiosis.
*The Neocallimastigomycota were earlier placed in the phylum Chytridomycota. Members of this small phylum are anaerobic organisms, living in the digestive system of larger herbivorous mammals and possibly in other terrestrial and aquatic environments. They lack mitochondria but contain hydrogenosomes of mitochondrial origin. As the related chrytrids, neocallimastigomycetes form zoospores that are posteriorly uniflagellate or polyflagellate.
* The Zygomycota contain the taxa, Zygomycetes and Trichomycetes, and reproduce sexually with meiospores called zygospores and asexually with sporangiospores. Black bread mold ("Rhizopus stolonifer") is a common species that belongs to this group; another is "Pilobolus", which is capable of ejecting spores several meters through the air. Medically relevant genera include "Mucor", "Rhizomucor", and "Rhizopus". Molecular phylogenetic investigation has shown the Zygomycota to be a polyphyletic phylum with evidence of paraphyly within this taxonomic group. [cite journal|author=White MM, James TY, O'Donnell K, Cafaro MJ, Tanabe Y, Sugiyama J.|year=2006|title=Phylogeny of the Zygomycota based on nuclear ribosomal sequence data|journal=Mycologia|volume=98|pages=872–884|pmid=17486964|doi=10.3852/mycologia.98.6.872] ]
* Members of the Glomeromycota are fungi forming arbuscular mycorrhizae with higher plants. Only one species has been observed forming zygospores; all other species solely reproduce asexually. The symbiotic association between the Glomeromycota and plants is ancient, with evidence dating to 400 million years ago.* The Ascomycota, commonly known as sac fungi or ascomycetes, constitute the largest taxonomic group within the Eumycota. These fungi form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus. This division includes morels, a few mushrooms and truffles, single-celled yeasts (e.g., of the genera "Saccharomyces", "Kluyveromyces", "Pichia", and "Candida"), and many filamentous fungi living as saprotrophs, parasites, and mutualistic symbionts. Prominent and important genera of filamentous ascomycetes include "Aspergillus", "Penicillium", "Fusarium", and "Claviceps". Many ascomycetes species have only been observed undergoing asexual reproduction (called anamorphic species), but molecular data has often been able to identify their closest teleomorphs in the Ascomycota. Because the products of meiosis are retained within the sac-like ascus, several ascomyctes have been used for elucidating principles of genetics and heredity (e.g. "Neurospora crassa").
* Members of the Basidiomycota, commonly known as the club fungi or basidiomycetes, produce meiospores called basidiospores on club-like stalks called basidia. Most common mushrooms belong to this group, as well as rust (fungus) and smut fungi, which are major pathogens of grains. Other important Basidiomyces include the maize pathogen,"Ustilago maydis", human commensal species of the genus "Malassezia", and the opportunistic human pathogen, "Cryptococcus neoformans".
Phylogenetic relationships with other fungus-like organisms
Because of some similarities in morphology and lifestyle, the slime molds (myxomycetes) and water molds (oomycetes) were formerly classified in the kingdom Fungi. Unlike true fungi, however, the cell walls of these organisms contain cellulose and lack chitin. Slime molds are unikonts like fungi, but are grouped in the Amoebozoa. Water molds are diploid bikonts, grouped in the Chromalveolate kingdom. Neither water molds nor slime molds are closely related to the true fungi, and, therefore, taxonomists no longer group them in the kingdom Fungi. Nonetheless, studies of the oomycetes and myxomycetes are still often included in mycology textbooks and primary research literature.
It has been suggested that the nucleariids, currently grouped in the Choanozoa, may be a sister group to the eumycete clade, and as such could be included in an expanded fungal kingdom. [cite book |title=The Mycota: A Comprehensive Treatise on Fungi as Experimental Systems for Basic and Applied Research |last=Esser |first=Karl |coauthors=Paul A. Lemke |year=1994 |publisher=Springer |isbn=3540580085 ]
ee also
*Bioaerosol
*Carnivorous fungus
*Entomopathogenic fungi
*Fusicoccin
*List of fungal orders
*MycoBank
*Plant pathology
*Wood-decay fungus
*Pathogenic fungi
Notes and references
Further reading
*Alexopoulos, C.J., Charles W. Mims, M. Blackwell et al., "Introductory Mycology, 4th ed." (John Wiley and Sons, Hoboken NJ, 2004) ISBN 0-471-52229-5
*Arora, David. (1986). "Mushrooms Demystified: A Comprehensive Guide to the Fleshy Fungi". 2nd ed. Ten Speed Press. ISBN 0898151694
* Deacon JW. (2005). "Fungal Biology" (4th ed). Malden, MA: Blackwell Publishers. ISBN 1-4051-3066-0.
* Kaminstein D. (2002). [http://www.healthatoz.com/healthatoz/Atoz/ency/mushroom_poisoning.jsp Mushroom poisoning] .
External links
* [http://mycology.cornell.edu/ The WWW Virtual Library: Mycology]
* [http://www.mykoweb.com/ MykoWeb]
* [http://www.ilmyco.gen.chicago.il.us/Terms/TermsFrame.html Illinois Mycological Association Mycological Glossary]
* [http://tolweb.org/fungi Tree of Life web project: Fungi]
* [http://bugs.bio.usyd.edu.au/Mycology/contents.shtml "Fungal Biology"] , "University of Sydney, School of Biological Sciences", June, 2004. – Online textbook
* [http://www.mycolog.com/fifthtoc.html "The Fifth Kingdom"] – Online textbook
* [http://www.speciesfungorum.org/ CABI Bioscience Databases] - Includes "Index Fungorum" genus and species names and top-down hierarchy
* [http://img.jgi.doe.gov/cgi-bin/pub/main.cgi?section=TaxonList&page=lineageMicrobes&phylum=Fungi Comparative Analysis of Fungal Genomes] (at DOE's IMG system)
* [http://www.iq.usp.br/wwwdocentes/stevani/ Fungi Bioluminescence Laboratory] - Chemistry Institute, University of São Paulo, Brazil