Hypha
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2008-06-17T11:39:00Z
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[[Image:Penicillium.jpg|thumb|300px|Hyphae of ''[[Penicillium]]'']]
A '''hypha''' (plural '''hyphae''') is a long, branching filamentous cell of a [[fungus]], and also of unrelated [[Actinobacteria]].<ref name=Brock>{{cite book | author = Madigan M; Martinko J (editors). | title = Brock Biology of Microorganisms | edition = 11th ed. | publisher = Prentice Hall | year = 2005 | id = ISBN 0131443291 }}</ref> In fungi, hyphae are the main mode of vegetative growth, and are collectively called a [[mycelium]].
A hypha consists of one or more [[cell (biology)|cell]]s surrounded by a tubular [[cell wall]]. In most fungi, hyphae are divided into cells by internal cross-walls called '''septa''' (singular [[septum]]). Septa are usually perforated by pores large enough for [[ribosome]]s, [[Mitochondrion|mitochondria]] and sometimes [[cell nucleus|nuclei]] to flow among cells. The structural polymer in fungal cell walls is typically [[chitin]] (in contrast plants have [[cellulose|cellulosic]] cell walls, and animal cells lack walls). Some Fungi however, have non septate hypha, meaning their hypha are not separated by septa.
Hyphae grow at their tips. During tip growth, cell walls are extended by the external assembly and polymerization of cell wall components, and the internal production of new cell membrane. The '''Spitzenkorper''' is an intracellular organelle associated with tip growth. It is composed of an aggregation of membrane-bound vesicles containing cell wall components. The vesicles travel to the cell membrane via the [[cytoskeleton]], and dump their contents outside the cell by the process of [[exocytosis]]. Vesicle membranes contribute to growth of the cell membrane while their contents form new cell wall. As a hypha extends, [[septa]] may be formed behind the growing tip to partition each hypha into individual cells. Hyphae can branch through bifurcation of a growing tip, or by the emergence of a new tip from an established hypha.
Hyphae may be modified in many different ways to serve specific functions. Some [[parasitism|parasitic]] fungi form [[haustorium|haustoria]] that function in absorption within the host cells. The [[Arbuscular mycorrhiza|arbuscules]] of [[mutualism|mutualistic]] [[mycorrhiza]]l fungi serve a similar function in nutrient exchange, so are important in assisting nutrient and water absorption by [[plant]]s. Hyphae are found enveloping the [[gonidia]] in [[lichen]]s, making up a large part of their structure. In nematode-trapping fungi, hyphae may be modified into trapping structures such as constricting rings and adhesive nets. [[Mycelial cord|Cords]] can be formed to transfer nutrients over larger distances.
== Types of hyphae ==
=== Classification based on cell division ===
*Septate (with septa)
**'''Pseudohyphae''' are not true septate hyphae and are distinguished from "true hyphae" by their method of growth, relative frailty and lack of [[cytoplasm]]ic connection between the cells. They are most often found in yeasts as the result of a sort of incomplete [[budding]] where the cells remain attached after division.
*Aseptate or [[coenocyte|coenocytic]] (without septa).
=== Classification based on cell wall and overall form ===
Characteristics of hyphae can be important in fungal classification. In [[Basidiomycota|basidiomycete]] taxonomy, hyphae that comprise the [[sporocarp (fungi)|fruiting body]] can be identified as generative, skeletal, or binding hyphae.<ref name=IMA>{{cite web | title=Hyphal System |publisher = Illinois Mycological Association | url = http://www.ilmyco.gen.chicago.il.us/Terms/trimi142.html | accessdate=2007-02-11}}</ref>
*'''Generative''' hyphae are relatively undifferentiated and can develop reproductive structures. They are typically thin-walled, occasionally developing slightly thickened walls, usually have frequent septa, and may or may not have [[clamp connection]]s. They may be embedded in mucilage or gelatinized materials.
*'''Skeletal''' hyphae are of two basic types, the classical form is thick-walled and very long in comparison to the frequently septate generative hyphae, unbranched or rarely branched, with little cell content. They have few septa and lack clamp connections.
*'''Fusiform skeletal''' hyphae are the second form of skeletal hyphae. Unlike typical skeletal hyphae these are swollen centrally and often exceedingly broad, hence giving the hypha a [[fusiform]] shape.
*'''Binding''' hyphae are thick-walled and frequent branched. Often they resemble deer antlers or defoliated trees because of the many tapering branches.
Based on the generative, skeletal and binding hyphal types, in 1932 [[E. J. H. Corner]] applied the terms monomitic, dimitic, and trimitic to hyphal systems, in order to improve the classification of [[polypore]]s.<ref name=Corner_1932>{{cite journal | author = Corner EJH | title = A Fomes with two systems of hyphae | journal = Trans. Brit. Mycol. Soc.| year = 1932 | volume = 17 | pages = 51–81}}</ref><ref name=Cunningham_1954>{{cite journal | author = Cunningham GH | title = Taxonomic Problems of some Hymenomycetes | journal = Transactions and Proceedings of the Royal Society of New Zealand | year = 1954-55 | volume = 82 | pages = 893–6 | url=http://rsnz.natlib.govt.nz/volume/rsnz_82/rsnz_82_04_010220.html }}</ref>
*Every fungus must contain generative hyphae. A fungus which only contains this type, as do fleshy mushrooms such as [[agaric]]s, is referred to as '''monomitic'''.
*Skeletal and binding hyphae give leathery and woody fungi such as [[polypore]]s their tough consistency. If a fungus contains all three types (example: ''[[Trametes versicolor|Trametes]]''), it is called '''trimitic'''.
*If a fungus contains generative hyphae and just one of the other two types, it is called '''dimitic'''. In fact dimitic fungi almost always contain generative and skeletal hyphae; there is one exceptional genus, ''[[Laetiporus]]'' that includes only generative and binding hyphae.
*Fungi that form [[fusiform]] skeletal hyphae bound by generative hyphae are said to have '''sarcodimitic''' hyphal systems. A few fungi form fusiform skeletal hyphae, generative hyphae, and binding hyphae. These are said to have '''sarcotrimitic''' hyphal systems. These terms were introduced by [[E.J.H. Corner]] in 1966 <ref name=Corner_1966>{{cite journal |author = Corner EJH | title = Monograph of cantharelloid fungi| journal = Ann. Bot. Mem.| year = 1966 | volume = 2 | pages = 1–255}}</ref>
=== Classification based on refractive appearance ===
Hyphae are described as '''gloeoplerous''' ('''gloeohyphae''') if their high refractive index gives them an oily or granular appearance under the microscope. These cells may be yellowish or clear ([[hyaline]]). They can sometimes selectively be coloured by sulphovanillin or other reagents. Also the specialized cells termed [[cystidia]] can be gloeoplerous.<ref>See glossary of Meinhard Moser, translated by Simon Plant: ''Keys to Agarics and Boleti'' (Roger Phillips 1983) ISBN 0-9508486-0-3.</ref><ref>See section "Microscopic features ..." of [http://www.clarku.edu/faculty/dhibbett/workshops%20and%20outreach/2006%20workshop%20documents/collecting%20and%20id.pdf 2006 Summer Workshop in Fungal Biology for High School Teachers], Hibbett lab, Biology Department, Clark University, "Guidelines for collecting and identifying macrofungi (basidiomycetes)".</ref>
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==References==
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==See also==
* [[Yeast]]
== External links ==
{{wiktionary|hypha}}
* [http://www.knowledgebank.irri.org/diseaseDiag/2.11._Hypha.htm Diagram] of branching hyphae, emphasizing septa
* Close-up [http://botit.botany.wisc.edu/images/130/Protista_I/Oomycota_Saprolegnia/Coenocytic_hyphae_MC.html light micrograph] of coenocytic hyphae
* [http://www.microbiologybytes.com/introduction/myc1.html MicrobiologyBytes: Introduction to Mycology]
* [http://129.215.156.68/Movies/hypha.htm Hyphal growth and branching] movies by P.C. Hickey and N. Read, University of Edinburgh
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