Metarhizium anisopliae
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 Tsetse flies killed by M. anisopliae
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| Metarhizium anisopliae (Metchnikoff) Sorokin |
Metarhizium anisopliae, formerly known as Entomophthora anisopliae, is a fungus that grows naturally in soils throughout the world and causes disease in various insects by acting as a parasite; it thus belongs to the entomopathogenic fungi. It is known to infect over 200 insect species, including termites. It is currently being used as a biological insecticide to control a number of pests such as grasshoppers, termites, thrips, etc. and its use in the control of malaria-transmitting mosquitos is under investigation.
The disease caused by the fungus is called green muscardine disease because of the green colour of its spores. When these mitotic (asexual) spores (called conidia) of the fungus come into contact with the body of an insect host, they germinate and the hyphae that emerge penetrate the cuticle. The fungus then develops inside the body eventually killing the insect after a few days; this lethal effect is very likely aided by the production of insecticidal cyclic peptides (destruxins). The cuticle of the cadaver often becomes red. If the ambient humidity is high enough, a white mould then grows on the cadaver that soon turns green as spores are produced. Most insects living near the soil have evolved natural defenses against entomopathogenic fungi like M. anisopliae. This fungus is therefore locked in an evolutionary battle to overcome these defenses, which has led to a large number of isolates (or strains) that are adapted to certain groups of insects.
Some isolates are so specific that they have attained variety status, like Metarhizium anisopliae var. acridum, which almost exclusively infects grasshoppers in the suborder Caelifera of the Orthoptera. Various research groups, including the international LUBILOSA Programme, have identified key technical challenges in the development of mycoinsecticide products including: isolate selection, mass production and delivery systems (formulation and application). In other words insect control (mortality) depends on factors like the number of spores applied against the insect host, the formulation and weather conditions. Oil-based formulations allow the application of fungal spores under dry conditions, and is compatible with existing Ultra-Low Volume (ULV) application techniques for locust control.
I.I. Mechnikov named Metarhizium anisopliae after the insect species it was originally isolated from, the beetle Anisoplia austriaca. It is a mitosporic fungus with asexual reproduction for which a teleomorph has not yet been discovered. Since Cordyceps taii was shown to be the teleomorph of Metarhizium taii, it seems therefore likely that the one of M. anisopliae will also turn out to be a Cordyceps species. However, it is also possible that some, if not most, strains of M. anisopliae have lost the capability of reproducing sexually.
The fungus does not appear to infect humans or other animals and is considered safe as an insecticide. The microscopic spores are typically sprayed on affected areas. A possible technique for malaria control is to coat mosquito nets or cotton sheets attached to the wall with them.
In August 2007, a team of scientists at the Indian Institute of Chemical Technology discovered a more efficient way of producing biodiesel which uses lipase, an enzyme produced in significant quantities by Metarhizium anisopliae; as opposed to other reactions which use enzymes that require heat in order to become active, the reaction that uses lipase runs at room temperature. The fungus is now a candidate for mass production of the enzyme.
[edit] See also
- Beauveria bassiana, the fungus that causes white muscardine disease in various insects
- Biological insecticides
[edit] References
- Burges, H.D. (ed.) 1998 Formulation of Microbial Biopesticides, beneficial microorganisms, nematodes and seed treatments Publ. Kluwer Academic, Dordrecht, 412 pp.
- Bateman, R.P., Carey, M., Batt, D., Prior, C., Abraham, Y., Moore, D., Jenkins, N. and Fenlon, J. 1996 Screening for virulent isolates of entomopathogenic fungi against the desert locust, Schistocerca gregaria (Forskål). Biocontrol Science and Technology 6: 549-560.
- Cloyd, Raymond A. The Entomopathogenic Fungus Metarhizium anisopliae, Midwest Biological Control News, Vol VI No 7
- Driver, F., Milner, R. J., Trueman, W. H.A. 2000 A Taxonomic revision of Metarhizium based on sequence analysis of ribosomal DNA. Mycological Research 104: 135-151
- Freimoser, F. M., Screen, S., Bagga, S., Hu, G and St. Leger, R.J. 2003. EST analysis of two subspecies of Metarhizium anisopliae reveals a plethora of secreted proteins with potential activity in insect hosts. Microbiology 149: 239-247.
- Lomer C.J., Bateman R.P., Johnson D.L., Langwald, J. and Thomas, M. 2001 Biological Control of Locusts and Grasshoppers. Annual Review of Entomology 46: 667-702.
- McNeil, Donald G. Jr., Fungus Fatal to Mosquito May Aid Global War on Malaria, The New York Times, 10 June 2005
- Prior, C., Greathead, D.J., 1989 Biological control of locusts: the potential for the exploitation of pathogens. FAO Plant Protection Bulletin 37: 37-48
- Rowe, Aaron Fungi Make Biodiesel Efficiently at Room Temperature, Wired Science, 20 August 2007
- Screen, S.E., Hu, G. and St. Leger, R. J. 2002. Transformants of Metarhizium anisopliae sf. anisopliae overexpressing chitinase from Metarhizium anisopliae sf. acridum show early induction of native chitinase but are not altered in pathogenicity to Manduca sexta . Journal of Invertebrate Pathology 78: 260-266.
- Thomas, M.H., Blanford, S 2003 Thermal biology in insect-parasite interactions. Trends in Ecology and Evolution 18: 344-350.
[edit] External links
- Index Fungorum record, links to a list of synonyms
- LUBILOSA Programme, website of the programme that developed Metarhizium for locust control
- Fungi Make Biodiesel Efficiently at Room Temperature
