Difference between revisions of "Fungus" - New World Encyclopedia

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Fungi

Orange saprotrophic fungus.

Scientific classification

Domain:	Eukaryota
Kingdom:	Fungi L., 1753

Divisions

Chytridiomycota
Deuteromycota
Zygomycota
Glomeromycota
Ascomycota
Basidiomycota

Fungus growing on a tree in Borneo

The fungi (singular fungus) make up one of the kingdoms into which living things are divided by biologists. They differ from bacteria in having a cell nucleus; from plants in not making their own food through photosynthesis; and from animals in not being mobile and in absorbing nutrition externally rather than internally. Fungi include mushrooms, yeasts, moulds, mildews, and others. Athough often un-noticed or misunderstood by humans fungi play a vital role in the earth's ecosystems.

Structure

Fungi may be single-celled or multicellular. Multicellular fungi are composed of networks of long hollow tubes called hyphae. The hyphae often aggregate in a dense network known as mycelium. The mycelium grows through the medium on which the fungus feeds. Because fungi are embedded in the medium in which they grow, most often soil, they are often not visible to the naked eye.

Although fungi lack true organs, the mycelia may become organized into more complex reproductive structures called fruiting bodies, or sporocarps, when conditions are right. "Mushroom" is the common name given to the above-ground fruiting bodies of many fungal species. Although these above-ground structures are the most conspicuous to humans, they make up only a small portion of the entire fungal body. Some fungi form rhizoids, which are underground root-like structures that provide support and transport nutrients from the soil to the rest of the mycelium.

The largest organism in the world is purported to be a single Armillaria ostoyae individual growing in a forest in eastern Oregon. The underground mycelial network may cover as much as 2200 acres).

Hyphae as seen under a log

Fungus growing on fallen tree trunks in Belize.

Role in Nature

Most fungi live by decomposing the remains of dead plants and animals. This releases carbon and other materials back to the environment where they can be reused by plants. Other fungi are parasites, living in or on the bodies of plants and animals and sometimes causing diseases. Others live in symbiotic mutually beneficial relationships with other organisms. Lichens are a combination of an algae, which provides food through photosynthesis, and a fungus, which provides protection to the algae. Leaf-cutter ants and some species of termites live in a symbiotic relationship with fungi in which the insects protect the fungi and provide them with plant material to decompose while the fungi provide food for the insects.

The most important symbiotic relationship in which fungi take part was unknown until the last part of the Twentieth Century. That is mycorrhizas, the relationship between fungi and plants. Specialized fungi live on the roots of most (perhaps 95 percent of all) land plants. The hyphae of the fungi extend out into the soil and form a network of fibers which in effect extend the root system of the plant enabling it to more effectively absorb water and minerals. The plant provides the fungi with nutrients produced by its photosynthesis. Most plants could not thrive without a partnership with these fungi.

Fungi and Humans

Besides their tremendous indirect importance to humans because of their role in the life cycles of plants, fungi also affect us directly in many ways.

Mushrooms

Truffles

Truffles are the underground fruiting bodies of several types of fungi which have a

Yeast

Penicillin

Fungal Diseases

Mushrooms, truffles, and yeast are fungi used for food.  Penicillin and other antibiotics have been derived from the natural defenses of molds and other fungi against bacteria.  Fungi are also being used as biological defenses against insects, and other fungi.

Fungi can also be harmful to human interests. They are one of the main causes of spoiling food as well as clothing, wood, paper, and other organic materials. Some types can cause human diseases, athletes foot being the most common but others much more serious. Others cause diseases in animals and plants. Dutch elm disease, caused by a fungus introduced from Europe, killed off almost all of the native elm trees in North America.

Types of fungi

The major divisions (phyla) of fungi are mainly classified based on their sexual reproductive structures. Currently, five divisions are recognized:

File:K 1033CR08-9 Yellow fungus on stalk.jpg

Yellow fungus

The Chytridiomycota are commonly known as chytrids. These fungi produce zoospores that are capable of moving on their own by simple flagella.
The Zygomycota are known as zygomycetes and reproduce sexually. Black bread mold (Rhizopus stolonifer) is a common species that belongs to this group, another is Pilobolus, which shoots specialized structures through the air for several meters.
Members of the Glomeromycota are also known as the arbuscular mycorrhizal fungi. Only one species has been observed forming zygospores; all other species only reproduce asexually.
The Ascomycota, commonly known as sac fungi or ascomycetes, form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus. This division includes morels, some mushrooms and truffles, as well as single-celled yeasts and many species that have only been observed undergoing asexual reproduction.
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 and smut fungi, which are major pathogens of grains.

Although the water molds and slime molds have traditionally been placed in kingdom Fungi and are still studied by mycologists, they are not true fungi. Unlike true fungi, the water molds and slime molds do not have cell walls made of chitin. In the 5-kingdom system, they are currently placed in kingdom Protista.

Reproduction

Fungi may reproduce sexually or asexually. In asexual reproduction, the offspring are genetically identical to the “parent” organism (they are clones). During sexual reproduction, a mixing of genetic material occurs so that the offspring exhibit traits of both parents. Many species can use both strategies at different times, while others are apparently strictly sexual or strictly asexual. Sexual reproduction has not been observed in some fungi of the Glomeromycota and Ascomycota. These are commonly referred to as Fungi imperfecti or Deuteromycota.

Yeasts and other unicellular fungi can reproduce simply by budding, or “pinching off” a new cell. Many multicellular species produce a variety of different asexual spores that are easily dispersed and resistant to harsh environmental conditions. When the conditions are right, these spores will germinate and colonize new habitats.

References
ISBN links support NWE through referral fees

Kaminstein, D. (2002). Mushroom poisoning. Retrieved 2006-01-05.

External links

Credits

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Fungus ^history

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History of "Fungus"

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@@ Line 19: / Line 19: @@
 ==Structure==
-[[Image:Hyphae.JPG|thumb|left|Hyphae as seen under a log]]
+Fungi may be single-celled or multicellular. Multicellular fungi are composed of networks of long hollow tubes called hyphae. The hyphae often aggregate in a dense network known as mycelium. The mycelium grows through the medium on which the fungus feeds. Because fungi are embedded in the medium in which they grow, most often soil, they are often not visible to the naked eye.
-Fungi may be single-celled or multicellular. Multicellular fungi are composed of networks of long hollow tubes called hyphae. The hyphae often aggregate in a dense network known as mycelium. The mycelium grows through the medium on which the fungus feeds. Because fungi are embedded in the medium in which they grow, they are often not visible to the naked eye.
 Although fungi lack true organs, the mycelia may become organized into more complex reproductive structures called fruiting bodies, or sporocarps, when conditions are right. "Mushroom" is the common name given to the above-ground fruiting bodies of many fungal species. Although these above-ground structures are the most conspicuous to humans, they make up only a small portion of the entire fungal body. Some fungi form rhizoids, which are underground root-like structures that provide support and transport nutrients from the soil to the rest of the mycelium.
-Fungi reproduce both sexually and asexually.  Most often a fungus will give off spores which are carried by the wind, water, or by animals and can grow into new fungi if they land in the right environment.
 The largest organism in the world is purported to be a single ''Armillaria ostoyae'' individual growing in a forest in eastern Oregon. The underground mycelial network may cover as much as 2200 acres).
+[[Image:Hyphae.JPG|thumb|left|Hyphae as seen under a log]]
 [[Image:Fungi Belize.jpg|right|thumb|200px|Fungus growing on fallen tree trunks in [[Belize]].]]
@@ Line 40: / Line 36: @@
 ==Fungi and Humans==
-==Overview==
+Besides their tremendous indirect importance to humans because of their role in the life cycles of plants, fungi also affect us directly in many ways.
-Although often inconspicuous, fungi occur in every environment on [[earth]] and play very important roles in most [[ecosystems]]. Many fungi are major [[decomposer]]s of dead plant and animal matter in [[forest]]s and many other environments. Some fungi are [[predators]] of [[nematodes]], which they capture using an array of devices such as constricting rings or adhesive nets ([http://www.uoguelph.ca/~gbarron/MISC2003/illustra.htm see illustrations]). Other types are [[parasite]]s on plants and animals, including [[human]]s. They are responsible for numerous [[disease]]s, such as [[athlete’s foot]] and [[ringworm]] in humans and [[Dutch elm disease]] in plants. Other fungi are partners in [[symbiosis|symbiotic]] relationships with other organisms. For example, [[lichen]]s are formed by a symbiotic relationship between [[algae]] or [[cyanobacteria]] and fungi. Most [[vascular plant]]s benefit from a symbiosis between their [[root]]s and fungi.
-Fungi have a long history of use by humans. Many types of [[mushroom]]s and other fungi are eaten, including [[button mushroom]]s, [[shiitake mushroom]]s, and [[oyster mushroom]]s. Of course, many [[species]] of mushrooms are [[poison]]ous and are responsible for numerous cases of [[sickness]] and [[death]] every year. A type of fungus called [[yeast]] is used in baking [[bread]] and [[ferment]]ing [[alcoholic beverage]]s. Fungi are also used to produce industrial chemicals like [[lactic acid]], and even to make stonewashed [[jeans]]. Some types of fungi are ingested for their [[psychedelic drug|psychedelic]] properties, both [[recreational drug|recreationally]] and religiously (as [[entheogen]]s) (see main article, ''[[Psychedelic mushroom]]'').
+===Mushrooms===
+===Truffles===
+Truffles are the underground fruiting bodies of several types of fungi which have a
+===Yeast===
+===Penicillin===
+===Fungal Diseases===
-===Types of fungi===
+ Mushrooms, truffles, and yeast are fungi used for food.  [[Penicillin]] and other antibiotics have been derived from the natural defenses of molds and other fungi against bacteria.  Fungi are also being used as biological defenses against insects, and other fungi.
-The major divisions ([[phyla]]) of fungi are mainly classified based on their sexual [[reproduction|reproductive]] structures. Currently, five divisions are recognized:
-[[Image:K_1033CR08-9_Yellow_fungus_on_stalk.jpg|right|thumb|200px|Yellow fungus]]
+Fungi can also be harmful to human interests.  They are one of the main causes of spoiling food as well as clothing, wood, paper, and other organic materials.  Some types can cause human diseases, athletes foot being the most common but others much more serious.  Others cause diseases in animals and plants.  Dutch elm disease, caused by a fungus introduced from Europe, killed off almost all of the native elm trees in North America.
-* The [[Chytridiomycota]] are commonly known as chytrids. These fungi produce zoospores that are capable of moving on their own through liquid menstrua by simple [[flagellum|flagella]].
+==Types of fungi==
-* The [[Zygomycota]] are known as zygomycetes and reproduce sexually with meiospores called zygospores. [[Black bread mold]] (''Rhizopus stolonifer'') is a common species that belongs to this group, another is ''[[Pilobolus]]'', which shoots specialized structures through the air for several meters.
-* Members of the [[Glomeromycota]] are also known as the arbuscular mycorrhizal fungi. Only one species has been observed forming zygospores; all other species only reproduce asexually. This is an ancient association, with evidence dating to 350 mybp.
-* The [[Ascomycota]], commonly known as sac fungi or ascomycetes, form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus. This division includes [[morel]]s, some [[mushroom]]s and [[truffle]]s, as well as single-celled [[yeast]]s and many species that have only been observed undergoing asexual reproduction. 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 [[basidiospore]]s on club-like stalks called [[basidium|basidia]]. Most common [[mushroom]]s belong to this group, as well as [[rust (fungus)]] and [[smut (fungus)|smut fungi]], which are major pathogens of grains.
-Although the [[water mold]]s and [[slime mold]]s have traditionally been placed in kingdom Fungi and are still studied by mycologists, they are not true fungi. Unlike true fungi, the water molds and slime molds do not have cell walls made of [[chitin]]. In the [[kingdom (biology)|5-kingdom system]], they are currently placed in kingdom [[Protist]]a.
+The major divisions ([[phyla]]) of fungi are mainly classified based on their sexual reproductive structures. Currently, five divisions are recognized:
+[[Image:K_1033CR08-9_Yellow_fungus_on_stalk.jpg|right|thumb|200px|Yellow fungus]]
+* The Chytridiomycota are commonly known as chytrids. These fungi produce zoospores that are capable of moving on their own  by simple flagella.
+* The Zygomycota are known as zygomycetes and reproduce sexually. Black bread mold (''Rhizopus stolonifer'') is a common species that belongs to this group, another is ''Pilobolus'', which shoots specialized structures through the air for several meters.
+* Members of the Glomeromycota are also known as the arbuscular mycorrhizal fungi. Only one species has been observed forming zygospores; all other species only reproduce asexually.
+* The Ascomycota, commonly known as sac fungi or ascomycetes, form meiotic spores called ascospores, which are enclosed in a special sac-like structure called an ascus. This division includes morels, some mushrooms and truffles, as well as single-celled yeasts and many species that have only been observed undergoing asexual reproduction.
+* 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  and smut fungi, which are major pathogens of grains.
+Although the water molds and slime molds have traditionally been placed in kingdom Fungi and are still studied by mycologists, they are not true fungi. Unlike true fungi, the water molds and slime molds do not have cell walls made of chitin. In the 5-kingdom system, they are currently placed in kingdom Protista.
-===Reproduction===
+==Reproduction==
-Fungi may reproduce sexually or asexually. In [[asexual reproduction]], the [[offspring]] are genetically identical to the “parent” organism (they are [[Cloning|clones]]). During [[sexual reproduction]], a mixing of [[gene|genetic material]] occurs so that the offspring exhibit traits of both parents. Many species can use both strategies at different times, while others are apparently strictly sexual or strictly asexual. Sexual reproduction has not been observed in some fungi of the [[Glomeromycota]] and [[Ascomycota]]. These are commonly referred to as Fungi imperfecti or [[Deuteromycota]].
-Yeasts and other unicellular fungi can reproduce simply by [[budding]], or “pinching off” a new cell. Many multicellular species produce a variety of different asexual spores that are easily dispersed and resistant to harsh environmental conditions. When the conditions are right, these spores will [[germination|germinate]] and colonize new [[Habitat (ecology)|habitat]]s.
+Fungi may reproduce sexually or asexually. In asexual reproduction, the offspring are genetically identical to the “parent” organism (they are [[cloning|clones]]). During sexual reproduction, a mixing of genetic material occurs so that the offspring exhibit traits of both parents. Many species can use both strategies at different times, while others are apparently strictly sexual or strictly asexual. Sexual reproduction has not been observed in some fungi of the Glomeromycota and Ascomycota. These are commonly referred to as Fungi imperfecti or Deuteromycota.
-Sexual reproduction in fungi is somewhat different from that of animals or plants, and each fungal division reproduces using different strategies. Fungi that are known to reproduce sexually all have a [[haploid]] stage and a [[diploid]] stage in their life cycles. Ascomycetes and basidiomycetes also go through a [[dikaryotic]] stage, in which the [[cell nucleus|nuclei]] inherited by the two parents do not fuse right away, but remain separate in the hyphal cells (see [[heterokaryosis]]).
+Yeasts and other unicellular fungi can reproduce simply by budding, or “pinching off” a new cell. Many multicellular species produce a variety of different asexual spores that are easily dispersed and resistant to harsh environmental conditions. When the conditions are right, these spores will germinate and colonize new habitats.
-In zygomycetes, the haploid hyphae of two compatible individuals fuse, forming a [[zygote]], which becomes a resistant [[zygospore]]. When this zygospore germinates, it quickly undergoes [[meiosis]], generating new haploid hyphae and asexual [[sporangiospore]]s. These sporangiospores may then be distributed and germinate into new genetically-identical individuals, each producing their own haploid hyphae. When the hyphae of two compatible individuals come into contact with one another, they will fuse and generate new zygospores, thus completing the cycle.
+==References==
-In ascomycetes, when compatible haploid hyphae fuse with one another, their nuclei do not immediately fuse. The dikaryotic hyphae form structures called [[ascus|asci]] (''sing.'' ascus), 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 to form new haploid mycelium. Asexual [[Conidium|conidia]] may be produced by the haploid mycelium. Many ascomycetes appear to have lost the ability to reproduce sexually and reproduce only via conidia.
-Sexual reproduction in basidiomycetes is similar to that of ascomycetes. Sexually compatible haploid hyphae fuse to produce a dikaryotic mycelium. This leads to the production of a [[basidiocarp]]. The most commonly-known basidiocarps are mushrooms, but they may also take many other forms. Club-like structures known as [[basidia]] generate haploid [[basidiospores]] following karyogamy and meiosis. These basidiospores then germinate to produce new haploid myceliumata.
-==Edible and poisonous fungi==
-Some of the most well-known types of fungi are the [[Edible mushroom|edible]] and [[Mushroom poisoning|poisonous mushrooms]]. Many species are commercially raised, but others must be harvested from the wild. Button mushrooms (''Agaricus bisporus'') are the most commonly eaten species, used in salads, soups, and many other dishes. [[Button mushroom|Portobello mushrooms]] are also members of this species, but grow to a much larger size. Other commercially-grown mushrooms that have gained in popularity in the West and are often available fresh in grocery stores include oyster mushrooms, shiitakes, and [[enoki]] mushrooms.
-There are many more mushroom species that are [[Mushroom hunting|harvested from the wild]] for personal consumption or commercial sale. [[Morel|Morels]], [[chanterelle]]s, [[truffles]], [[Craterellus|black trumpets]], and [[porcini]] mushrooms (also known as king boletes) all command a high price on the market. They are often used in gourmet dishes.
-It is also a common practice to permit the growth of specific species of [[mold]] in certain types of cheeses that give them their unique flavor. This mold is non-toxic and is safe for human consumption. Examples of this are Blue Cheese and [[Stilton_cheese|Stilton Cheese]].
-Hundreds of mushroom species are toxic to humans, causing anything from upset stomachs to [[hallucination]]s to death. Some of the most deadly belong to the genus ''[[Amanita]]'', including ''[[Amanita virosa|A. virosa]]'' (the "Destroying Angel") and ''[[Amanita phalloides|A. phalloides]]'' (the "Death Cap"). Stomach cramps, vomiting, and diarrhea usually occur within 6-24 hours after ingestion of these mushrooms, followed by a brief period of remission (usually 1-2 days). Patients often fail to present themselves for treatment at this time, assuming that they have recovered. However, within 2-4 weeks [[liver]] and [[kidney]] failure leads to death if untreated. There is no antidote for the toxins in these mushrooms, but [[kidney dialysis]] and administration of [[corticosteroids]] may help. In severe cases, a liver transplant may be necessary (Kaminstein 2002). 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 leave it alone.
-[[Amanita muscaria|Fly agaric]] mushrooms (''A. muscaria'') are also responsible for a large number of poisonings, but these cases rarely result in death. The most common symptoms are nausea and vomiting, drowsiness, and hallucinations. In fact, this species is used ritually and recreationally for its hallucinogenic properties. However, if it is taken in over a long period of time (regularly over more than six months), this species might cause a temporary loss of sight, which can last from several minutes to an hour.
-==Fungi in the biological control of pests==
-Many fungi compete with other organisms, or directly infect them. Some of these fungi are considered beneficial because they can restrict, and sometimes eliminate, the populations of noxious organisms like pest insects, [[mites]], [[weed]]s, [[nematodes]] and other fungi, such as those that kill plants. There is much interest on the manipulation of these beneficial fungi for the [[biological control]] of pests. Some of these fungi can be used as [[biopesticides]], like the ones that kill insects ([[entomopathogenic fungi]]). Specific examples of fungi that have been developed as [[bioinsecticide]]s are ''[[Beauveria bassiana]]'', ''[[Metarhizium anisopliae]]'', [[Hirsutella]], ''[[Paecilomyces fumosoroseus]]'', and ''[[Verticillium lecanii]]'' (=''[[Lecanicillium lecanii]]'' ).
-==References==
 * {{cite web
   | url = http://www.healthatoz.com/healthatoz/Atoz/ency/mushroom_poisoning.jsp