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C. coronatus grows on potato dextrose, Sabouraud and cornmeal agar. The strains that are adapted to human infection readily grow at 37C. It produces flat waxy colorless to yellowish white to brownish tan cultures that form aerial mycelium. The colonies grow quickly and can reach a diameter of 6 cm in 48 hours. As a colony becomes older it may obtain a powdery texture and the lid of the petri dish will become covered in sticky conidia.
C. coronatus has wide vegetative coenoyctic hyphae that are 6 to 15 µm in size. The conidiophores are 8-12 µm in width by 60-90µm in length and they produce primary conidia that are 25 to 45 µm in diameter. Secondary spores tend to be smaller. The villose conidia’s spikes are 10 to 15 µm in length.
Conidiobolus coronatus is found on every continent. It was first isolated in plant detritus and is the most commonly isolated species of the genus Conidiobolus. Although, it prefers warmer, wetter, tropical and subtropical climates around the equator, it has been isolated in soil from the United Kingdom and eastern United States. The majority of the human infections occur in Western African rain forests in Nigeria, Cameroon, the Ivory Coast and Zaire. Interestingly, there are fewer cases of animal zygomycosis in these regions where human infection are more common. Infections have been documented in India, Colombia, Brazil, Jamaica, Coast Rica, the Congo, and the United States.
Although, C. coronatus is cosmopolitan, only about 150 cases of human disease have been observed. The fungus usually infects men that are agriculture or outdoor workers between the ages of 20-60. The male to female rate of infection is 8:1. The individuals that are infected are often immunocompromised, but in many cases the patients have been healthy with no physical abnormalities.
Conidiobolus coronatus is a ubiquitous saprobe of plant debris. It is an opportunistic pathogen and in humans it is the major causative agent of rhinoentomophthoromycosis. Rhinoentomophthoromycosis is the condition of having an Entomophthorales fungus in the nose. This word has four roots. Rhino comes from rhinos which meant nose in Greek. Entomophthoro comes from the fungal order Entomophthorales . Myco is Latin for fungus and sis stands for condition of.
C. coronatus has been known to parasitize other mammals, such as horses, llamas, dolphins, and chimpanzees. It was first described by Costantin in 1897 in France and was first isolated in 1961 by Chester Emmons and Charles Bridges from nasal granulomata of three horses in Australia. A granulomata is a bulge that forms because the cells of the immune system attempts to wall off the fungus. In 1965, Bras et al discovered and isolated the first human case in the Caribbean on the Grand Cayman Island.
C. coronatus is also an opportunistic parasite of many insects and it has been proposed as an insecticide. An insecticide is either a chemical or an organism that can kill insects that damage crops. C. coronatus infects a large variety of insects; however it is an especially effective parasite of Lepidoptera, which is the family that includes butterflies and moths.
C. coronatus lacks an apparent sexual life cycle because it is heterothallic and does not produce zygospores. However, the asexual life cycle is very complex. When, primary conidia are produced from the hyphae, the columella projects into the conidia. The primary conidia are released by an eversion mechanism which is characteristic of the genus Conidiobolus. Due to turgor pressure the conidia release and both the bottom of the conidia and the tip of the conidiophore project. The primary conidia are globose, multinucleate, and have two cells walls that are connected. The primary conidia can germinate by forming hyphae from multiple germ tubes. In addition, the primary conidia can germinate by repetitively forming into secondary conidia. The secondary conidia are oriented by light and are also released by eversion. There are various forms of secondary conidia. The primary conidia can produce short conidiophores containing microconidia which form on multiple sterigmata. The microconidia allow greater dispersal. In addition, there are various secondary resting spore types observed such as villose conidia, chlamydospores, and locriconidia. Resting spore allow survival in unfavorable growth conditions. C. coronatus is unique in its genus because it produces villose conidia, from which it gets its name because the spikes look like those of a crown, and microconidia. Oddly, when Costantin first described C. coronatus he did not observe the villose spores.
Secondary conidia production is regulated by the availability of nutrients and pH. Nutrient rich or mildly acidic or basic medium produces germination of germ tubes to form hyphae, while nutrient poor or extremely acidic and basic medium will lead to the production of secondary conidia. Younger cultures and cultures in humid environments tend to produce the microconidia, while older cultures tend to produce the villose conidia.
C. coronatus prefers warmer and wetter climates. There is a correlation between increased C. coronatus levels and the yearly peak of rainfall. In addition, it only germinates conidia in humidity greater than 95%, which is likely why disease is only observed in warmer, wetter, subtropical or tropical regions around the equator.
There are 27 species of the genus Conidiobolus. Only 19 species form zygospores and have a sexual cycle. All of the species have primary conidia and produce repetitive secondary conidia. However, the secondary conidia that are produced depend on the species. Microconidia have been observed in 10 species. All but six species have been originally isolated from plant detritus. Furthermore, C. coronatus, C. stromeides, and C. psuedococcus have been shown to infect insects.
There are three species of Entomophthorales that infect humans: Basidiobolus haptosporus, Conidiobolus coronatus, and Conidiobolus incongruus. The four diagnostic features of C. coronatus are production of microconidia and villose spores, projecting tips of the columella and the conidia after the eversion dispersal, and no production of zygospores.
C. incongruus very rarely causes disease. Unlike C. coronatus, C. incongruus is seldom isolated from the environment. It does not produce villose resting spores. It is characterized by production of microconidia, and it is homothallic and produces zygospores that lack a beak.
Basidiobolus haptosporus is characterized by very special shaped cylindrical conidiophores that form from the primary conidia during repetitive conidia production. They also have a sexual cycle in which they form distinctive beaked zygospores. In addition, they produce secondary conidia called capillospores with a sticky end. The sticky end is used to attach to insects for the dispersal of the spores.
Rhinoentomophthoromycosis caused by C. coronatus results from the inhalation of fungal spores that then implant in the nasal mucosa. The fungus then spreads throughout the subcutaneous of the face and can infect the paranasal sinuses. In certain case studies, it appeared that nose picking had led to small sores that became infected by the fungus! Mothers are always right! The lesions are painless and form nodules in the subcutaneous throughout the face. These nodules can cause the individual to look like a hippopotamus. If there is swelling inside the nasal cavity, it can lead to the sensation of nasal obstruction. However, the disease never passes the blood-brain barrier or into the lungs and thus in only a couple cases did it cause human death. The few case-studies of Bras et al 1965, Segura et al 1981, Costa et al 1991, and Do Valle et al 2001 are included in the works cited, for the readers that are interested in viewing pictures or reading case studies of the disease.
The excretion of serine proteases that are produced when the conidia are released is the most important virulence factor of C. coronatus. The serine proteases are excreted into the subcutaneous space, where they cause the release of amino acids by degrading proteins. This mode of virulence is postulated because there is an increase in the production of serine proteases during columella and conidia formation. C coronatus also produces tissue destroying collagenases and lipases.
The anti-fungal treatment for C. coronatus can vary from patient to patient because the drugs have varying success. Potassium iodide, septrin, amphotericin B, ketoconazole and intraconazole are the drugs that have been used most commonly.
There has been speculation on the use of C. coronatus as a control of insect pests that destroy crops. C. coronatus parasitizes a wide variety of insects however the family Lepidoptera is especially susceptible. It infects Galleria mellonella or Honeycomb Moth larvae that are pest of commercial honey or fig production and Bemisia tabaci or sweetpotato whitefly that damages sweetpotatoes. It can also infect Hylotrupes bajalus, wood-boring beetles, Calandaria granaria, grain weevils, Tenebrio molitor, mealworms, Spodoptera littoralis, the Egyption Cotton Leafworm and Dendrolimus pini, the pine-tree lappet.
Fungal infections of insect hosts are usually through the penetration of the insect exoskeleton. Once it has pierced through the exoskeleton, C. coronatus is a rapid killer. It takes 1-2 days to kill its host. A fungus can kill an insect via tissue destruction, production of mycotoxins, or depletion of nutrients. In infections caused by C. coronatus, mycotoxins are the cause of insect death. As C. coronatus spreads in the insect, it produces mycotoxins made of proteins. These mycotoxins cause damage to the muscles, however oddly the fat storage of the insects is not affected. In infected G. mellonella the infected sites became darker due to the production of melanin. After killing the host, C. coronatus will develop saphrophytically.
However, a disadvantage of C. coronatus for use as an insecticide is demonstrated by its infection of the pea aphid or Acyrthosiphon pison. Unlike the famous genus Cordyceps, C. coronatus cannot control its host’s behavior. The aphid releases its proboscis from its host plant and falls to the ground. C. coronatus then has limited its chance of dispersal to new hosts, because it will sporulate on the ground far away from the pea aphid colonies.
Conidiobolus coronatus is a saprotrophic fungus,[1] first described by Costantin in 1897 as Boudierella coronata.[2] Though this fungus has also been known by the name Entomophthora coronata, the correct name is Conidiobolus coronatus.[3] C. coronatus is able to infect humans and animals, and the first human infection with C. coronatus was reported in Jamaica in 1965.[4]
Originally, C. coronatus was considered to be a part of the genus Boudierella,[2] however it was later transferred to the genus Conidiobolus by Saccardo and Sydow.[2] The fungus was also treated in the genus Entomophthora,[5] and the name Entomophthora coronata remains a widely used synonym.[3] Another synonym attributed to C. coronatus is Conidiobolus villosus by G.W. Martin in 1925 due to the characteristic presence of villi.[6]
Conidiobolus coronatus produces rapidly growing colonies that appear fuzzy and are flat.[4][6][7] In their early stages, the colonies are both glabrous and adherent.[6] In terms of colour, young C. coronatus colonies appear creamy gray,[4] however as it ages, the colony adopts a tan to light brown colour.[6] When grown on specific medium (Sabouraud-glucose agar with 0.2% yeast extract or potato dextrose agar (PDA) at 21 °C), C. coronatus colonies can reach approximately 4–5 cm in diameter within 3 days, demonstrating their rapid growth.[7] When the fungus is grown at higher temperatures of about 37 °C, furrow and fold formation can be seen.[6]
Conidiobolus coronatus reproduces asexually and produces thin-walled hyphae which occur singly or in clusters,[8] with very few septa.[4][8] At times, the hyphae will demonstrate an eosinophilic halo surrounding their edges,[8] this halo has been termed the Splendore-Hoeppli phenomenon.[9] C. coronatus hyphae can easily be visualized when hematoxylin and eosin staining is performed, however they cannot be visualized via PAS or silver staining.[9] The hyphae have unbranched sporangia,[4] and some of these round sporangia exhibit short extensions, aptly named secondary spores.[4] The single celled round sporangia, as well as the secondary spores, get ejected from the short sporangiophores, and they can travel up to 30mm upon ejection.[8] If the medium the sporangia and spores land on is nutrient-dense, they will germinate and form one or more hyphal tubes, and the fungus will then continue its development and growth.[8] Conidiobolus has three possible developmental pathways: (i) the fungus can remain in reproductive mode and form one or more secondary spores, (ii) the fungus may form a vegetative germ tube or (iii) it may not germinate at all.[3] If the sporangia germinate through the development of a vegetative germ tube, the germ tube will then develop into a mycelium and go on to produce many sporangia and sporangiospores.[3] If the fungus germinates through the formation of secondary spores, these secondary spores will usually be slightly smaller than the parent spores.[3] The secondary spores may also go on to produce many smaller microspores.[3] In young cultures, the C. coronatus spores have a smooth appearance, however as they mature, the spores gradually become covered with short hair like projections called villi.[1][3] The presence of villi is characteristic of C. coronatus.[6] Growth of the fungus in vivo shows a histologic pattern similar to that seen in other Zygomycota infections.[6]
Fungal growth is affected by the presence of optimal nutrients necessary for growth, by the presence of minerals, by temperature, by pH and by osmotic pressure.[3][7] The presence of organic nutrients in the medium that C. coronatus finds itself in favors the formation of vegetative germ tubes, with glucose inducing vegetative germ growth far more effectively than asparagine.[3] In terms of necessary nutrients for growth and survival, glucose and trehalose are both good sources of carbon for C. coronatus, other adequate sources of carbon are fructose, mannose, maltose, glycerol, oleate, stearate, palmitate and casamino acids, whereas galactose, starch and glycogen are all poor sources of carbon for C. coronatus.[7] When looking at nitrogen, complex nitrogen sources seem to be best suited for optimal C. coronatus growth, however L-asparagine, ammonium salts, L-aspartic acid, glycine, L-alanine, L-serine, N-acetyl-D-glucosamine and urea can all adequately be used by the fungus as nitrogen sources to varying extents.[7] This fungus is unable to utilize nitrate as a nitrogen source.[7] Certain minerals are able to stimulate fungal growth, for C. coronatus these minerals are Magnesium and Zinc.[7] In terms of temperature effects on fungal growth, the temperature at which C. coronatus growth is at an optimal stage on agar is 27 °C,[7] and the minimum temperature at which it is able to grow on agar is 6 °C.[7] Though there is no growth seen below 6 °C, good survival of C. coronatus has been demonstrated at temperatures of 1 °C.[7] Finally, the maximum growth temperature of C. coronatus on agar is 33 °C, this maximum growth temperature increases to 40 °C when the fungus is grown in liquid culture.[7] In terms of pH effects on C. coronatus, the optimal pH broad range of growth for this fungus is pH 5.5 to pH 7, however sub-optimal growth can occur anywhere within the range of pH 3.5 to pH 8.[7] In terms of pH dependent physiology, there is more frequent production of germ tubes on mildly acidic or neutral media (range of pH 5 to pH 7) with the greatest percent of germination occurring at pH 5.[3] In addition, the percentage of spores that produce secondary spores is far greater on acidic media than on both neutral and basic media.[3] In addition to organic nutrient and mineral presence, temperature and pH, osmotic pressure also has an effect on C. coronatus growth and dispersal. The spores of this fungus are more likely to germinate at lower osmotic pressures, and any medium with osmotic pressures greater than 10 atm will almost entirely inhibit germination of this fungus.[3]
Conidiobolus coronatus produces forcibly discharged sporangia, which show phototropic orientation.[5][6] Phototropic orientation aims growth and spore dispersal towards the most intense light source, thereby increasing the efficiency of dispersal.[3] This orientation towards the most intense light source can also be seen as a survival mechanism for the fungus as it increases the possibility that the sporangia will be dispersed in the least obstructed direction and to the greatest distance.[3] The forcible discharge is affected by the size of the spore, with smaller secondary spores being discharged to greater distances and therefore having a greater chance at becoming air borne and landing on a medium that is nutritionally favourable for fungal growth.[7] The growing zone of C. coronatus shows a light-mediated reorganization, with a weakness and thinning of the cell wall being seen in the area of future growth.[3] Both primary and secondary spores of C. coronatus show phototropic orientation, however it is imprecise and becomes increasingly imprecise the greater the lights' angle of incidence.[3] Upon further observation of the imprecise phototropic orientation, it can be seen that the sporangia seem to aim their dispersal above the source of light, which may be a compensation mechanism to assure that the fungus has the ability to disperse at the greatest possible distance, while maintaining its dispersal orientation towards the light.[3] Though the fungus shows phototropic orientation, albeit imprecise, the formation and discharge of secondary spores is shown to occur in darkness as well, however it seems to always requires high moisture levels.[3][7]
Secondary dispersal through the formation of secondary spores is a survival mechanism exhibited by C. coronatus.[3] This mechanism consists of the first spore producing a secondary spore if it lands on a nutritionally unfavourable medium, this secondary spore then gets discharged onto a different spot on the medium, or onto a completely different medium, in hopes of greater nutrient availability.[3] These secondary, replicative spores are globose and elongate in physiology.[7] Once the spore has been discharged, all subsequent developmental events are triggered, including germination.[3] Sporangial germination, either through secondary spore formation or vegetative germ tube formation, seems to be increasingly dependent on the time elapsed since discharge, rather than on the external environmental factors, however these external factors do still play a role.[3] The spores formed by C. coronatus during asexual reproduction are globose, villose and multiplicative in some isolates, and have at least seven nuclei per spore.[5] This presence of villose and multiplicative spores is what differentiates C. coronatus from the genus Entomophthora.[5] Though C.coronatus is classified under Zygomycota, it does not produce zygospores and therefore does not undergo sexual reproduction.[5]
It has been demonstrated that C. coronatus produces lipolytic, chitinolytic and proteolytic enzymes,[7] especially extracellular proteinases, namely serine proteases which are optimally active at pH 10 and 40 °C.[10][11] Serine proteases are a diverse group of bacterial, fungal and animal enzymes whose common element is an active site composed of serine, histidine and aspartic acid.[10] The serine proteases produced by C. coronatus are involved in the forcible discharge of sporangia and sporangiospores, in addition it has also been suggested that these proteases may have a function in the pathogenesis of human disease caused by C. coronatus.[10] The serine proteases secreted by this fungus show great activity and thermostability, making them suitable for commercialization in the leather and detergent industries,[10][11] as well for the recovery of silver from discarded photographic films.[11] The genome of C. coronatus is 39.9 Mb in length with a total of 10,572 postulated protein-encoding genes.[12]
Conidiobolus coronatus is an inhabitant of soil around the world,[9] possessing a tropical and universal distribution.[1] Due to its saprophytic nature,C. coronatus is mainly found on decaying and dead leaves.[3]
Conidiobolus coronatus is the causative fungal agent of chronic rhino facial zygomycosis.[8][13] Chronic rhinofacial zygomycosis is a painless swelling of the rhinofacial region that can cause severe facial disfigurement.[8][13] Rhinofacial zygomycosis caused by C. coronatus has been reported in humans, horses, dolphins, chimpanzees and other animals.[8][10] In addition to the rhino facial zygomycosis cases,C. coronatus is also pathogenic to mosquitoes Culex quinquefasciatus and Aedes taeniorhyncus, to the Guadaloupean parasol ant Acromyrmex octospinosus, to root maggots Phorbia brassicae, as well as to aphids and termites.[7] The vast majority of human cases of rhino facial zygomycosis caused by C. coronatus have occurred in central and west Africa, with a few cases having been reported in Colombia, Brazil and the Caribbean. Veterinary cases have been reported throughout the United States and Australia as well as other parts of the world.[8]
Focusing on human infection, C. coronatus mainly infects healthy adults, especially males.[1] The pattern of a C. coronatus infection is similar to infections caused by other members of the Zygomycota.[8] The rhinofacial zygomycosis pattern of infection can manifest when C. coronatus spores enter the nasal cavities through inhalation or through trauma of the nasal cavities.[13] The infection starts in the nose and invades the subcutaneous tissue but rarely disseminates because the agent is not angio-invasive.[1][8] Following invasion of the subcutaneous tissue, the characteristic rhinofacial masses develop.[8] These masses are bumpy and uneven, and over time, they end up reducing the size of the individuals' nasal passages by pushing on the septum, causing symptoms such as nasal discharge, chronic sinusitis and complete obstruction of nasal passages.[10] Chronic, long standing infection can lead to morbidity.[9] A possible course of treatment is the surgical removal of the masses.[8] Currently, there are no prevention strategies or specific risks identified for C. coronatus infection, and antifungal prophylaxis is not warranted.[9] Reduction in disease prevalence and morbidity hinges on early detection and treatment.[9] Recently demonstrated in HIV infected patient with first line ART resistance with delayed antifungal response[14]
{{cite book}}: |first1= has generic name (help) Conidiobolus coronatus is a saprotrophic fungus, first described by Costantin in 1897 as Boudierella coronata. Though this fungus has also been known by the name Entomophthora coronata, the correct name is Conidiobolus coronatus. C. coronatus is able to infect humans and animals, and the first human infection with C. coronatus was reported in Jamaica in 1965.
Conidiobolus coronatus je grzib[5], co go nojprzōd ôpisoł Costantin, a terŏźnõ nazwã doł mu A. Batko 1964. Conidiobolus coronatus nŏleży do zorty Conidiobolus i familije Ancylistaceae.[6][7] Żŏdne podgatōnki niy sōm wymianowane we Catalogue of Life.[6]
Conidiobolus coronatus je grzib, co go nojprzōd ôpisoł Costantin, a terŏźnõ nazwã doł mu A. Batko 1964. Conidiobolus coronatus nŏleży do zorty Conidiobolus i familije Ancylistaceae. Żŏdne podgatōnki niy sōm wymianowane we Catalogue of Life.
冠耳霉（学名：Conidiobolus coronatus）是属于虫霉目新月霉科耳霉属的一种真菌，寄生在蚜科、毛蠓科、叶蝉科等昆虫上，并广布于各种植物的腐烂组织甚至活组织。该种分布于中国、印度、日本、以色列、澳大利亚、坦桑尼亚、尼日利亚、喀麦隆、科特迪瓦、乍得、美国、墨西哥、古巴、巴西、百慕大、法国、瑞士、瑞典、捷克、比利时、波兰等地。[1]
这是一篇與真菌類相關的小作品。你可以通过编辑或修订扩充其内容。 冠耳霉（学名：Conidiobolus coronatus）是属于虫霉目新月霉科耳霉属的一种真菌，寄生在蚜科、毛蠓科、叶蝉科等昆虫上，并广布于各种植物的腐烂组织甚至活组织。该种分布于中国、印度、日本、以色列、澳大利亚、坦桑尼亚、尼日利亚、喀麦隆、科特迪瓦、乍得、美国、墨西哥、古巴、巴西、百慕大、法国、瑞士、瑞典、捷克、比利时、波兰等地。
