Aspergillus flavus: Difference between revisions

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{{CZ:Biol_201:_General_Microbiology/EZnotice}}
{{subpages}}
{{Taxobox
| color = blue
| name =Aspergillus Flavus 
| image = Aspergillus_flavus_01.jpg‎
| regnum = Fungi
| phylum =  Ascomycota
| classis =  Eurotiomycetes
| ordo =  Eurotiales
| familia =  Trichocomaceae
| genus =  Aspergillus
| species =  A. flavus
| binomial = Aspergillus flavus
| binomial_authority = 
}}
==Description and significance==
'''''Aspergillus flavus''''' is a filamentous fungus.  It produces a mycotoxin called [[aflatoxin B]] that is carcinogenic.<ref name=aflavus>[http://www.aspergillusflavus.org/aflavus/ ''Aspergillus flavus''] hosted by aspergillusflavus.org</ref> It causes liver damage and is one of the [[mycotoxin]]s used as a biologcal weapon<ref name=four> [Mold-Help.org. "Aspergillus."] hosted by Moled-help.org</ref>.  When crops are infected with ''A. flavus'' their value decreases because of the potential human or animal exposure to the aflatoxin.<ref name=two> [Mellon J, Cotty P, Dowd M. Aspergillus flavus hydrolases: their roles in pathogenesis and substrate utilization. Applied Microbiology & Biotechnology [serial online]. December 2007;77(3):497-504. Available from: Academic Search Premier, Ipswich, MA. Accessed April 12, 2009]</ref>  ''A. flavus'' is mainly a [[saprophyte]], meaning it obtains its nutrients from dead or decaying material, but it can also be a pathogen to plants and animals including humans.<ref name=aflavus/>
==Pathology==
==Pathology==
''A. flavus'' is an opportunistic pathogen, which allows it to infect animals, humans and plants.  It is not virulent in healthy viable tissues. ''A. flavus'' targets seeds with poor viability. It infects seeds by entering wounds and holes from which insect larval have exited, and by entering from the vascular tissue. ''A. flavus'' can infect plants via its seeds or by being carried to the surface of the plant by insects or wind.  Also it can be colonized but not infected until the plant is matured.  ''A. flavus'' infects cotton by entering from natural openings and traveling up into the boll. In the boll the fungus can be there for twenty five days, not infecting the boll until matures.  In peanuts the fungus can infect seeds as well as the plant by penetrating the pods that peanuts grow in.<ref name=five>[KLICH M. Aspergillus flavus: the major producer of aflatoxin. Molecular Plant Pathology [serial online]. November 2007;8(6):713-722. Available from: Academic Search Premier, Ipswich, MA. Accessed April 15, 2009]</ref>
''A. flavus'' is an opportunistic pathogen, which allows it to infect animals, humans and plants.  It is not virulent in healthy viable tissues. ''A. flavus'' targets seeds with poor viability. It infects seeds by entering wounds and holes from which insect larval have exited, and by entering from the vascular tissue. ''A. flavus'' can infect plants via its seeds or by being carried to the surface of the plant by insects or wind.  Also it can be colonized but not infected until the plant is matured.  ''A. flavus'' infects cotton by entering from natural openings and traveling up into the boll. In the boll the fungus can be there for twenty five days, not infecting the boll until matures.  In peanuts the fungus can infect seeds as well as the plant by penetrating the pods that peanuts grow in.<ref name=five>[KLICH M. Aspergillus flavus: the major producer of aflatoxin. Molecular Plant Pathology [serial online]. November 2007;8(6):713-722. Available from: Academic Search Premier, Ipswich, MA. Accessed April 15, 2009]</ref>
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In humans ''A. flavus'' is associated with aflatoxicosis.  Symptoms of aflatoxicosis are abdominal pain, vomiting, pulmonary edema, convulsions, coma, liver damage, and death. <ref name=pathport>
In humans ''A. flavus'' is associated with aflatoxicosis.  Symptoms of aflatoxicosis are abdominal pain, vomiting, pulmonary edema, convulsions, coma, liver damage, and death. <ref name=pathport>
  It can also cause aspergillosis, a secondary respiratory infection in immuno-compromised patients.  In certain areas it is also the cause of infections.  <ref name=two>.  Infections ''A. flavus'' can cause are  corneal, otomycotic, and nasoorbital infections.  <ref name=three>[http://en.wikipedia.org/wiki/Aspergillus_flavus Accessed April 13, 2009] hosted by wikipedia.com</ref> ''A. flavus'' is also an allergen. It causes allergic bronchopulmonary aspergillosis. <sup>5</sup>
  It can also cause aspergillosis, a secondary respiratory infection in immuno-compromised patients.  In certain areas it is also the cause of infections.  <ref name=two>.  Infections ''A. flavus'' can cause are  corneal, otomycotic, and nasoorbital infections.  <ref name=three>[http://en.wikipedia.org/wiki/Aspergillus_flavus Accessed April 13, 2009] hosted by wikipedia.com</ref> ''A. flavus'' is also an allergen. It causes allergic bronchopulmonary aspergillosis. <sup>5</sup>
==Ecology==
''Aspergillus flavus'' can be found all over the world; however it is found to be abundant in places of warm temperature. Field contamination is mostly present in areas with high temperatures and drought.  It is also abundant in areas with temperate climates during warm drought years.  In the US it affects the corn crop in the south eastern area. <sup>5</sup>
''A. flavus'' grows in temperatures of 25-42˚C, but the optimal temperature for growth is 37˚C. It survives through winter as a [[mycelium]] or [[sclerotia]]. Sclerotia is a resistant structure that is developed into [[hyphae]] or [[conidia]].  The conidia are then scattered into air and soil by insects or wind.<ref name=aflavus/>
==Cell structure and metabolism==
''A. flavus'' is also known as a mold.  Like other molds it also grows by producing hyphae.  The network of hyphae, or mycelium,are responsible for secreting enzymes. The enzymes secreted are used to break down complex food sources.  The complex food sources are broken down into small molecules which are then absorbed by the myceilium, which uses the small molecules to grow.  Mycelium contain conidia or asexual spores, both the mycelium and conidia can be seen with the naked eye while the hyphae cannot.  Young conidia in A. flavus are yellow green and as the spores age they turn a darker green. ''A. flavus'' can use many nutrient sources but being a saphrophyte it uses primarily dead or decaying materials.<ref name=aflavus/> Being a saphrophyte is important for "A. flavus" life cylce because it allows the fungus to be present in dieing tissue of plants.  These dieing tissues which are infected with "A. flavus" stay in the soil allowing the "A. flavus" to infect other plants. <ref name= pathport>[http://pathport.vbi.vt.edu/pathinfo/pathogens/A-f.html] hosted by pathport.vbi.vt.edu</ref>
==Genome structure==
The genome of ''A. flavus'' strain NRRL 3357 has been sequenced. It has 2761 scaffolds and each scaffold has anywhere between 4.5 Mbp to 200 bp. It has approximately 13,487 genes and the average length of each gene is 1485 bp.<ref name=aflavus/>
==Application to Biotechnology==
The genome was sequenced at The Institute for Genomic Research in Maryland.  It has also been entered into the BLAST database.<ref name=aflavus/>
==Current Research==
With the sequencing of the genome done, current research is focused on using the sequence to understand the fungus, to yield crops that are resistant to the fungus and to determine tools to control the production of the aflatoxin. One of the ways that the control of the production of aflatoxin is being researched is to see how the use of chemicals can weaken the oxidative stress response. ( oxidative stress has been shown to increase the production of aflatoxin.)  There have been many unsuccessful experiments conducted on yielding ''A. flavus'' resistant crops of peanuts and corn.  Currently research is being done to cultivate genes that are resistant to ''A. flavus'', afflatoxin production and plant stress.  These genes will then be used to create resistant crops. 5
==References==
<references/>
2. Mellon J, Cotty P, Dowd M. Aspergillus flavus hydrolases: their roles in pathogenesis and substrate utilization. Applied Microbiology & Biotechnology [serial online]. December 2007;77(3):497-504. Available from: Academic Search Premier, Ipswich, MA. Accessed April 12, 2009
4. Mold-Help.org. "Aspergillus." Accessed April 13, 2009
5.     
6.      Cleveland T., Yu J., Fedorova N., Bhatnagar D., Payne G., Nierman W., Bennett J. Potential of Aspergillus flavus genomics for applications in biotecnology. Trends in Biotechnology. Vol. 27 No. 3. February 3, 2009.

Revision as of 17:38, 13 May 2009

Pathology

A. flavus is an opportunistic pathogen, which allows it to infect animals, humans and plants. It is not virulent in healthy viable tissues. A. flavus targets seeds with poor viability. It infects seeds by entering wounds and holes from which insect larval have exited, and by entering from the vascular tissue. A. flavus can infect plants via its seeds or by being carried to the surface of the plant by insects or wind. Also it can be colonized but not infected until the plant is matured. A. flavus infects cotton by entering from natural openings and traveling up into the boll. In the boll the fungus can be there for twenty five days, not infecting the boll until matures. In peanuts the fungus can infect seeds as well as the plant by penetrating the pods that peanuts grow in.[1]

In humans A. flavus is associated with aflatoxicosis. Symptoms of aflatoxicosis are abdominal pain, vomiting, pulmonary edema, convulsions, coma, liver damage, and death. Cite error: Closing </ref> missing for <ref> tag A. flavus is also an allergen. It causes allergic bronchopulmonary aspergillosis. 5

  1. ↑ [KLICH M. Aspergillus flavus: the major producer of aflatoxin. Molecular Plant Pathology [serial online]. November 2007;8(6):713-722. Available from: Academic Search Premier, Ipswich, MA. Accessed April 15, 2009]
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