Aspergillus flavus

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Aspergillus Flavus
Scientific classification
Kingdom: Fungi Phylum: Ascomycota Class: Eurotiomycetes Order: Eurotiales Family: Trichocomaceae Genus: Aspergillus Species: A. flavus
Binomial name
Aspergillus flavus

Description and significance

Aspergillus flavus is a filamentous fungus. It produces a mycotoxin called aflatoxin B that is carcinogenic. It causes liver damage and is one of the mycotoxins used as a biologcal weapon. When crops are infected with A. Flavus their value decreases because of the potential human or animal exposure to the aflatoxin. 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.

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 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 penetrate the pods that peanuts grow in.

In humans A. flavus is associated with aspergillosis, a secondary respiratory infection in immuno-compromised patients. In certain areas it is also the cause of infections. A. flavus is also an allergen. It causes allergic bronchopulmonary aspergillosis.

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.

Application to Biotechnology

The genome was sequenced at The Institute for Genomic Research in Maryland. It has also been entered into the BLAST database.

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

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.