| 词条 | Ophiocordyceps unilateralis |
| 释义 |
| image = Ophiocordyceps unilateralis.png | image_width = 240px | image_caption = Dead ants infected with Ophiocordyceps unilateralis | regnum = Fungi | divisio = Ascomycota | classis = Sordariomycetes | ordo = Hypocreales | familia = Ophiocordycipitaceae | genus = Ophiocordyceps | species = O. unilateralis | binomial = Ophiocordyceps unilateralis | binomial_authority = (Tul.) Petch (1931) | synonyms_ref = [1] | synonyms = Torrubia unilateralis Tul. (1865) Cordyceps unilateralis (Tul.) Sacc. (1883) }} Ophiocordyceps unilateralis is an entomopathogen, or insect-pathogenising fungus, discovered by the British naturalist Alfred Russel Wallace in 1859, and currently found predominantly in tropical forest ecosystems. O. unilateralis infects ants of the Camponotini tribe, with the full pathogenesis being characterized by alteration of the behavioral patterns of the infected ant. Infected hosts leave their canopy nests and foraging trails for the forest floor, an area with a temperature and humidity suitable for fungal growth; they then use their mandibles to affix themselves to a major vein on the underside of a leaf, where the host remains until its eventual death.[1] The process leading to mortality takes 4–10 days, and includes a reproductive stage where fruiting bodies grow from the ant's head, rupturing to release the fungus's spores. O. unilateralis is in turn also susceptible to fungal infection itself, an occurrence that can limit its impact on ant populations, which has otherwise been known to devastate ant colonies. O. unilateralis and related species are known to engage in an active secondary metabolism, among other reasons, for the production of substances active as antibacterial agents that protect the fungus-host ecosystem against further pathogenesis during fungal reproduction. Because of this secondary metabolism, an interest in the species has been taken by natural products chemists, with corresponding discovery of small molecule agents (e.g. of the polyketide family) of potential interest for use as human immunomodulatory, antiinfective, and anticancer agents. Systematics{{expand section|1=recent molecular phylogenetic information, ca. 2007, from Spatafora et al., see talk|small=no|date=February 2015}}The scientific name is sometimes written Ophiocordyceps unilateralis sensu lato, which means "in the broad sense". This is because the species is actually a complex of many species within O. unilateralis.[2] MorphologyThe species can be identified at the end of its lifecycle by its reproductive structure, consisting of a wiry yet pliant darkly pigmented stroma stalk extending from the back of the dead ant's head. The stalk has perithecia just below its tip.[4][5] The fungus infects ants, most known is the carpenter ants, in which the fungus creates a single stalk arising from the dorsal neck region on which the spore-bearing sexual structures are borne horizontally. Once infected with the fungus, the ant will climb down from its normal habitat and bite down on the underside of a leaf. This is known as "the death grip" and occurs in very specific locations.[3] Life cycleLike other fungi pathogenic to insects in the genus Ophiocordyceps, O. unilateralis targets a specific host species, the Camponotus leonardi ant. However, the fungus may parasitize other closely related species of ants with lesser degrees of host manipulation and reproductive success. The changes in the behavior of the infected ants are very specific, giving rise to the popular term "zombie ants", and are tuned for the benefit of the fungus. The spores of the fungus attach, and eventually break through the ant's exoskeleton using mechanical pressure and enzymes.[3] Yeast stages of the fungus spread in the ant's body and presumably produce compounds that affect the ant's hemocoel, utilizing the evolutionary trait of an extended phenotype to manipulate the behavioral patterns exhibited by the ant.[9] An infected ant exhibits irregularly timed full body convulsions that dislodge it to the forest floor.[4] The ant climbs up the stem of a plant and uses its mandibles with abnormal force to secure itself to a leaf vein, leaving dumbbell-shaped marks on it. The ants generally clamp to a leaf's vein at a mean height of 25.20 ± 2.46 cm above the forest floor,[9] on the northern side of the plant, in an environment with 94–95% humidity and temperatures between {{convert|20|and|30|C|F}}. Infections may lead to 20 to 30 dead ants per square meter.[5] "Each time, they are on leaves that are a particular height off the ground and they have bitten into the main vein [of a leaf] before dying." When the dead ants are moved to other places and positions, further vegetative growth and sporulation either fails to occur or results in undersized and abnormal reproductive structures.[9] A search of plant-fossil databases revealed similar marks on a fossil leaf from the Messel Pit, which is 48 million years old.[15][16] Once the mandibles of the ant are secured to the leaf vein, atrophy quickly sets in, destroying the sarcomere connections in the muscle fibers and reducing the mitochondria and sarcoplasmic reticula. The ant is no longer able to control the muscles of the mandible and will remain fixed in place. This lockjaw trait is popularly known as the death grip, and is essential in the fungus's lifecycle.[4] The fungus then kills the ant, and continues to grow as its hyphae invade more soft tissues and structurally fortify the ant's exoskeleton. More mycelia then sprout out of the ant, and securely anchor it to the plant substrate while secreting antimicrobials to ward off competition. When the fungus is ready to reproduce, its fruiting bodies grow from the ant's head and rupture, releasing the spores. This process takes four to ten days. Geographic distributionThe fungus occurs in the tropical forests of Thailand[21] as well as in the Brazilian rainforests.[16] Host impactO. unilateralis has been known to destroy entire ant colonies. In response, ants have the ability to sense that a member of the colony is infected; healthy ants will carry the dying one far away from the colony in order to avoid fungal spore exposure.[4][5]Throughout the life cycle, there are unique challenges that must be met by equally unique metabolic activities. The fungal pathogen must attach securely to the arthropod exoskeleton and penetrate it—avoiding or suppressing host defenses—then, control the behavior of the host before killing it; and finally, it must protect the carcass from microbial and scavenger attack.[3] Medicinal potentialThe Ophiocordyceps fungus contains various known metabolites, as well as a number of structurally uncharacterized substances; these natural products are reportedly being investigated as potential leads in discovery efforts toward immunomodulatory, antitumor, hypoglycemic, and hypocholesterolemic targets.[26] Six known naphthoquinone derivatives have been isolated from O. unilateralis, namely erythrostominone, deoxyerythrostominone, 4-O-methyl erythrostominone, epierythrostominol, deoxyerythrostominol, and 3,5,8-trihydroxy-6-methoxy-2-(5-oxohexa-1,3-dienyl)-1,4-naphthoquinone, which have shown activity in in vitro assays related to anti-malarial drug discovery.[27][28] There has also been research into the use of red naphthoquinone pigments made by O. unilateralis as a dye for food, cosmetic and pharmaceutical manufacturing processes.[29] O. unilaterlis produces naphthoquinone, which under acidic conditions shows a red color and under basic conditions shows a purple color. These pigments are stable against acid/alkaline conditions, light and non-cytotoxic, which makes them applicable food coloring as well as dyeing of other materials. These attributes also make it a prime candidate for anti-tuberculoid testing in secondary TB patients, by improving symptoms and enhancing immunity when combined with chemotherapeutic drugs.[6][7]Fungal hyperparasiteO. unilateralis suffers from an unidentified fungal hyperparasite, reported in the lay press as the "anti-zombie-fungus fungus", that results in only 6–7% of sporangia being viable, limiting the damage O. unilateralis inflicts on ant colonies. The hyperparasite moves in to attack Ophiocordyceps unilateralis as the fungal stalk emerges from the ant's cadaver, which can stop the stalk from releasing its spores.[8][9]The density of infected ants and graveyards of dead ants are numerous and spread throughout the surrounding area of the colony. Even though O. unilateralis is very virulent, only about 6.5% of all fruiting bodies are viable spore-producers. This is caused by the castration of the fungus by the hyperparasite, which may cause the limiting of the viable infectious spores. Ants also groom each other to combat microscopic organisms that could potentially harm the colony. This shows that the colony is not in as much danger as previously thought. Additional fungi grant beneficial assistance to the colony as well.[9] References1. ^{{cite journal | vauthors = Mongkolsamrit S, Kobmoo N, Tasanathai K, Khonsanit A, Noisripoom W, Srikitikulchai P, Somnuk R, Luangsa-ard JJ | title = Life cycle, host range and temporal variation of Ophiocordyceps unilateralis/Hirsutella formicarum on Formicine ants | journal = Journal of Invertebrate Pathology | volume = 111 | issue = 3 | pages = 217–24 | year = 2012 | pmid = 22959811 | doi = 10.1016/j.jip.2012.08.007 }} [10][11][12][13][14][15][16][17][18][19][20]2. ^{{cite journal | vauthors = Evans HC, Elliot SL, Hughes DP | title = Hidden Diversity Behind the Zombie-Ant Fungus Ophiocordyceps unilateralis: Four New Species Described from Carpenter Ants in Minas Gerais, Brazil | journal = PLoS ONE | volume = 6 | issue = 3 | pages = 1–9 | date = March 2011 | pmid = 21399679 | pmc = 3047535 | doi = 10.1371/journal.pone.0017024 | bibcode = 2011PLoSO...617024E }} 3. ^1 2 {{cite journal | vauthors = Evans HC, Elliot SL, Hughes DP | title = Ophiocordyceps unilateralis – A keystone species for unraveling ecosystem functioning and biodiversity of fungi in tropical forests? | journal = Communicative Integrative Biology | volume = 4 | issue = 5 | pages = 598–602 | date = September–October 2011 | pmid = 22046474 | pmc = 3204140 | doi = 10.4161/cib.4.5.16721 | doi-broken-date = 2018-09-25 }} 4. ^1 {{cite journal | vauthors = Hughes DP, Andersen SB, Hywel-Jones NL, Himaman W, Billen J, Boomsma JJ | title = Behavioral mechanisms and morphological symptoms of zombie ants dying from fungal infection |journal=BMC Ecology | volume = 11 | issue = 1 | pages = 13–22 | date = May 2011 | pmid = 21554670 | pmc = 3118224 | doi = 10.1186/1472-6785-11-13 | url = http://www.biomedcentral.com/1472-6785/11/13 }} 5. ^{{cite episode | last = Attenborough | first = David | title = Cordyceps: attack of the killer fungi | series = Planet Earth | url = https://www.youtube.com/watch?v=XuKjBIBBAL8 | publisher = BBC Worldwide | date = 3 November 2008 | accessdate = 2013-04-21}} 6. ^{{cite journal | vauthors = Isaka M, Kittakoop P, Kirtikara K, Hywel-Jones NL, Thebtaranonth Y | title = Bioactive substances from insect pathogenic fungi | journal = Acc. 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Res. | volume = 38 | issue = 10 | pages = 813–23 | year = 2005 | pmid = 16231877 | doi = 10.1021/ar040247r }} 7. ^{{cite journal | vauthors = Wang, Enlai DA, Zhong JI | title = A Retrospective Analysis of Cordyceps Anti-Tuberculosis Capsule Combined with Chemotherapy for 614 Cases of Secondary Tuberculosis | journal = Journal of Traditional Chinese Medicine | year = 2013 | volume = 15 }} 8. ^{{cite news | url = http://science.psu.edu/news-and-events/2012-news/Hughes4-2012 | publisher = Pennsylvania State University | title = The Zombie-Ant Fungus Is Under Attack, Research Reveals | date = 2012-05-02 | accessdate = 2013-03-04}} 9. ^1 {{cite journal | vauthors = Andersen SB, Ferrari M, Evans HC, Elliot SL, Boomsma JJ, Hughes DP | title = Disease Dynamics in a Specialized Parasite of Ant Societies | journal = PLoS ONE | volume = 7 | issue = 5 | page = e36352 | date = 2 May 2012 | pmid = 22567151 | pmc = 3342268 | doi = 10.1371/journal.pone.0036352 | bibcode = 2012PLoSO...736352A }} 10. ^1 2 {{cite journal | vauthors = Pontoppidan MB, Himaman W, Hywel-Jones NL, Boomsma JJ, Hughes DP | title = Graveyards on the move: The spatio-temporal distribution of dead Ophiocordyceps-infected ants | journal = PLoS ONE | volume = 4 | issue = 3 | pages = e4835 | date = 12 March 2009 | pmid = 19279680 | pmc = 2652714 | doi = 10.1371/journal.pone.0004835 | bibcode = 2009PLoSO...4.4835P }} 11. ^1 2 {{cite journal | vauthors = Sung GH, Hywel-Jones NL, Sung JM, Luangsa-Ard JJ, Shrestha B, Spatafora JW | title = Phylogenetic classification of Cordyceps and the clavicipitaceous fungi | journal = Studies in Mycology | volume = 57 | issue = 1 | pages = 5–59 | year = 2007 | pmid = 18490993 | pmc = 2104736 | doi = 10.3114/sim.2007.57.01 }} 12. ^1 {{cite news | url = https://www.sciencedaily.com/releases/2010/08/100818105730.htm | title = Fossil Reveals 48-Million-Year History of Zombie Ants | publisher = Science Daily | date = 18 August 2010 | accessdate = 2010-09-12}} 13. ^1 {{cite web | url = http://www.mycobank.org/MycoTaxo.aspx?Link=T&Rec=281145 | title = Ophiocordyceps unilateralis | website = MycoBank | publisher = International Mycological Association | accessdate = 2011-07-19}} 14. ^1 2 {{cite journal | vauthors = Hughes DP, Wappler T, Labandeira CC | title = Ancient death-grip leaf scars reveal ant fungal parasitism | journal = Biology Letters | volume = 7 | issue = 1 | pages = 67–70 | date = 23 February 2011 | pmid = 20719770 | pmc = 3030878 | doi = 10.1098/rsbl.2010.0521 | origyear = 18 August 2010 }} 15. ^1 2 3 {{cite journal | vauthors = Andersen SB, Gerritsma S, Yusah KM, Mayntz D, Hywel-Jones NL, Billen J, Boomsma JJ, Hughes DP | title = The life of a dead ant: The expression of an adaptive extended phenotype | journal = The American Naturalist | volume = 174 | issue = 3 | pages = 424–433 | date = September 2009 | pmid = 19627240 | doi = 10.1086/603640 | jstor = 10.1086/603640 }} 16. ^1 {{cite web | first = Katherine | last = Harmon | date = 31 July 2009 | url = http://www.scientificamerican.com/article.cfm?id=fungus-makes-zombie-ants | title = Fungus makes zombie ants do all the work | website = Scientific American | accessdate = 2010-08-22}} 17. ^1 {{cite journal | vauthors = Xiao JH, Zhong JJ | title = Secondary metabolites from Cordyceps species and their antitumor activity studies | journal = Recent Patents on Biotechnology | volume = 1 | issue = 2 | pages = 123–137 | year = 2007 | pmid = 19075836 | doi = 10.2174/187220807780809454 }} 18. ^1 {{cite journal | vauthors = Wongsa P, Tasanatai K, Watts P, Hywel-Jones N | title = Isolation and in vitro cultivation of the insect pathogenic fungus Cordyceps unilateralis | journal = Mycological Research | volume = 109 | issue = Pt 8 | pages = 936–940 | date = August 2005 | pmid = 16175796 | doi = 10.1017/S0953756205003321 }} 19. ^1 {{cite journal | vauthors = Unagul P, Wongsa P, Kittakoop P, Intamas S, Srikitikulchai P, Tanticharoen M | title = Production of red pigments by the insect pathogenic fungus Cordyceps unilateralis BCC 1869 | journal = Journal of Industrial Microbiology and Biotechnology | volume = 32 | issue = 4 | pages = 135–140 | date = April 2005 | pmid = 15891934 | doi = 10.1007/s10295-005-0213-6 }} 20. ^1 {{cite journal | vauthors = Kittakoopa P, Punyaa J, Kongsaeree P, Lertwerawat Y, Jintasirikul A, Tanticharoena M, Thebtaranonth Y | year = 1999 | title = Bioactive naphthoquinones from Cordyceps unilateralis | journal = Phytochemistry | volume = 52 | issue = 3 | pages = 453–457 | doi = 10.1016/S0031-9422(99)00272-1}} }} External links
7 : Fungi described in 1865|Fungi of Africa|Fungi of Asia|Fungi of South America|Ophiocordycipitaceae|Mind-altering parasites|Parasitic fungi |
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