Hyphomycetes

Hyphomycetes
Scientific classification
Kingdom: Fungi
orders

Hyphomycetales
Stilbellales
Tuberculariales

Hyphomycetes are a form classification of Fungi, part of what has often been referred to as Fungi imperfecti, Deuteromycota, or anamorphic fungi. Hyphomycetes lack closed fruit bodies, and are often referred to as moulds (or molds). Most hyphomycetes are now assigned to the Ascomycota, on the basis of genetic connections made by life-cycle studies or by phylogenetic analysis of DNA sequences; many remain unassigned phylogenetically. Identification of hyphomycetes is primarily based on microscopic morphology including: conidial morphology, especially septation, shape, size, colour and cell wall texture, the arrangement of conidia as they are borne on the conidiogenous cells (e.g. if they are solitary, arthrocatenate, blastocatenate, basocatenate, or gloiosporae), the type conidiogenous cell (e.g. non-specialized or hypha-like, phialide, annellide, or sympodial), and other additional features such as the presence of sporodochia or synnemata.[1] [2][3]

Taxonomic and nomenclatural history

Because asexual forms of fungi usually occur separately from their sexual forms, when microscopic fungi began to be studied in the early 19th century, it was often unknown when two morphologically different forms were actually part of one species. The tendency for some organisms to apparently only have asexual forms, or for their sexual forms to be discovered long after the asexual forms, meant that an independent taxonomy was developed for asexual fungi. Near the beginning of the 20th century, when it became clearer that many asexual and sexual forms were related, the concept of 'form taxa' was developed. The independent taxonomy of asexual forms was regarded as artificial, not representative of evolutionary relationships, and intended to be practical for identification purposes. The taxonomy of the sexual states was considered the true classification. The result was that many fungal species ended up with two accepted Latin binomials, one for the asexual form (or anamorph) and the other for the sexual form (teleomorph). This dual nomenclature was only abandoned in January 2012,[4] and the transition to a single name system, with one name representing all morphs of a fungus, is still incomplete.[5]

Ecological importance

Aquatic or Ingoldian hyphomycetes are common on submerged decaying leaves and other organic matter, especially in clean running water with good aeration. Colonised leaves fall from the tree into the river. Their branched, septate mycelium penetrates through the leaf surface and spreads through leaf tissue. Conidiophores project into the water and bear conidia, which are often sigmoid, branched or tetraradiate structures. Aquatic hyphomycetes play an important role in the breakdown of organic matter in rivers, because their extracellular enzymes break down leaf tissue, which in turn is made more palatable to invertebrates. Leaves with fungi (conditioned) are a more nutritious source of food than unconditioned leaves.[6]

Coprophilous or dung-loving hyphomycetes are part of the succession of fungi occurring on many kinds of herbivore faeces, playing an important role in breaking down cellulose.[7] Several species are found only on dung, such as Angulimaya sundara, Onychophora coprophila, Pulchromyces fimicola, Sphondylocephalum verticillatum and Stilbella fimetaria.

Entomogenous, entomopathogenic or insect-pathogenic hyphomycetes infect and kill insects (and spiders) and are especially diverse in tropical and subtropical regions, especially in Asia.[8] Most are asexual states of or phylogenetically related to the Ascomycete families, Cordycipitaceae and Ophiocordycipitaceae. Insect hosts are infected by asexual spores, which germinate and grow to fill the host body with mycelium or hyphal bodies, then produce sporulating structures on the insect carcass. They are often found on dead insects under bark or in soil, but some affect insect behaviour ("zombie fungus"), causing infected hosts to climb towards the light, ensuring that air-borne infective spores will be released higher up in the canopy of the forest or meadow.[9] Well-known entomogenous hyphomycetes are classified in Beauveria, Metarhizium and Tolypocladium; famous anamorphic generic names such as Akanthomyces, Gibellula, Hirsutella, Hymenostilbe and Isaria are now subsumed in genera formerly considered sexual, such as Cordyceps, Ophiocordyceps and Torubiella under fungal single-name nomenclature.[10] Species of Beauveria and Metarhizium show some promise as biological control agents against pest insects.[11] Tolypocladium inflatum was the original source of cyclosporine A, used as a drug to prevent rejection of organ transplants.[12]

Many food-borne fungi are hyphomycetes. Species of Penicillium and Aspergillus are particularly common agents of food spoilage and also produce important mycotoxins that affect human health.[13] Some species, such as Penicillium digitatum on citrus fruits, and Penicillium expansum on apples, are common on specific foods, while others are less specialized and grow on many different kinds of food.

Nematophagous or nematode-trapping hyphomycetes either live their life-cycles in the bodies of dead nematodes or trap and kill nematodes in order to supplement their nitrogen requirements.[14] Species of the hyphomycete genus Arthrobotrys, phylogenetically related to or being the asexual forms of Orbilia, produce constricting loops that quickly shut to grab nematodes, or non-constricting loops or hyphal networks that entangle nematodes, or sticky knobs that adhere to nematodes as they swim by. Attempts to exploit these fungi as biological control agents against agriculturally harmful nematodes have generally been unsuccessful.[15]

See also

References

  1. ↑ Kendrick, W.B.; Carmichael, J.W. (1973). Ainsworth, G.C.; Sparrow, F.K.; Sussman, A.S., eds. Hyphomycetes. The Fungi: An Advanced Treatise. Academic Press, New York. pp. 323–509. ISBN 0-12-045604-4.
  2. ↑ C. V. Subramanian (1982). Hyphomycetes. Academic Press.
  3. ↑ Seifert, K.A.; Kendrick, B.; Morgan-Jones, G.; Gams, W. (2011). The Genera of Hyphomycetes. CBS Fungal Biodiversity Centre, the Netherlands. pp. 1–997.
  4. ↑ Hibbett DS, Taylor JW (2013). "Fungal systematics: is a new age of enlightenment at hand?". Nature Reviews. Microbiology. 11 (2): 129–33. doi:10.1038/nrmicro2963. PMID 23288349.
  5. ↑ Hawkswrth DL. (2014). "Possible house-keeping and other draft proposals to clarify or enhance the naming of fungi within the International Code of Nomenclature for algae, fungi, and plants (ICN)". IMA Fungus. 5 (1): 31–7. doi:10.5598/imafungus.2014.05.01.04. PMC 4107894Freely accessible. PMID 25083404.
  6. ↑ Bärlocher F. (2011). The Ecology of Aquatic Hyphomycetes. Ecological Studies. 94. Springer. ISBN 978-3-642-76857-6.
  7. ↑ Seifert, K.A.; Kendrick, W.B.; Murase, G. (1983). A key to Hyphomycetes on dung. University of Waterloo Biology Series no. 27. pp. 1–62.
  8. ↑ Samson, R.A.; Evans, H.C.; Latgé, J.-P. (1988). Atlas of entomopathogenic fungi. Springer, Berlin, Germany.
  9. ↑ Hughes DP, Andersen SB, Hywel-Jones NL, Himaman W, Billen J, Boomsma JJ (2011). "Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection". BMC Ecology. 11 (13): 1–10. doi:10.1186/1472-6785-11-13. PMC 3118224Freely accessible. PMID 21554670.
  10. ↑ Quandt (2014). "Phylogenetic-based nomenclatural proposals for Ophiocordycipitaceae (Hypocreales) with new combinations in Tolypocladium". IMA Fungus. 5 (1): 121–134.
  11. ↑ Fernandes É, Bittencourt VR, Roberts DW (2012). "Perspectives on the potential of entomopathogenic fungi in biological control of ticks". Experimental Parasitology. 130 (3): 300–5. doi:10.1016/j.exppara.2011.11.004. PMID 22143088.
  12. ↑ Survase SA, Kagliwal LD, Annapure US, Singhal RS (2011). "Cyclosporin A — a review on fermentative production, downstream processing and pharmacological applications". Biotechnology Advances. 29 (4): 418–35. doi:10.1016/j.biotechadv.2011.03.004. PMID 21447377.
  13. ↑ Samson, R.A.; Houbraken, J.; Thrane, U.; Frisvad, J.C.; Andersen, B. (2010). Food and Indoor Fungi. CBS Laboratory Manual Series, no. 2.
  14. ↑ Barron, G.L. (1973). The Nematode-Destroying Fungi. Topics in Mycobiology No. 1. Canadian Biological Publications; Guelph, Ont., Canada.
  15. ↑ Waller PJ, Faedo M (1996). "The prospects for biological control of the free-living stages of nematode parasites of livestock". International Journal for Parasitology. 26 (8–9): 915–25. doi:10.1016/S0020-7519(96)80064-6. PMID 8923139.
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