Submitted to: Mycologia
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2004
Publication Date: 2/1/2005
Citation: Cary, J.W., Klich, M.A., Beltz, S.B. 2005. Characterization of aflatoxin-producing fungi outside of Aspergillus section flavi. Mycologia. 97:425-432.
Interpretive Summary: Aflatoxin and sterigmatocystin are related poisons produced by a number of mold species in the genus Aspergillus. Aflatoxin is the more toxic of the two, and allowable levels are regulated by governments around the world at between 5 and 20 parts per billion in foods intended for human consumption. A number of new species of Aspergillus have recently been found to produce aflatoxin, though at levels much lower than produced by the agriculturally important Aspergillus species, A. flavus. This is important because these species are not related to A. flavus. Discovery of a common link among all aflatoxin producing species could lead to new approaches for controlling production of this toxin. In addition, it is hoped that this research will help us to gain a better understanding of: 1) the evolutionary processes that have determined why certain species of aspergilli have retained the ability to produce aflatoxin while others have not and 2) the ecological significance connected with a mold's ability to produce aflatoxin. This research will benefit researchers in mycotoxicology and fungal phylogenetics.
Technical Abstract: Most aspergilli that produce aflatoxin are members of Aspergillus section Flavi, however isolates of several Aspergillus species not closely related to section Flavi also have been found to produce aflatoxin. Two of the species, Aspergillus ochraceoroseus and A. taiensis, are morphologically similar to members of Aspergillus section Circumdati. The other species have Emericella teleomorphs (Em. astellata and Em. venezuelensis) and are morphologically distinctive in having ascospores with large flanges. All of the aflatoxin-producing isolates were from tropical zones near oceans, yet none of them grew on artificial media at 37 deg C. Phylogenetic analyses were conducted on the these four species using A. parasiticus and Em. nidulans, (which produce aflatoxin and the aflatoxin precursor sterigmatocystin, respectively) for comparison. Two aflatoxin/sterigmatocystin biosynthesis genes and one housekeeping gene were used in the analyses. Results indicated that all of the new aflatoxin-producers are more closely related to one another and Em. nidulans than to A. parasiticus.