Description and Significance. Aspergillus is a member of the phylum Ascomycota. There are over 185 known species, about 20 of which are known to be harmful to humans and other animals.The most infamous species of this genus is Aspergillus flavus, which produces aflatoxin.Aflatoxin is a contaminant of nuts and grain.spergillus is a member of the phylum Ascomycota. There are over 185 known species, about 20 of which are known to be harmful to humans and other animals. The most infamous species of this genus is Aspergillus flavus, which produces aflatoxin. Aflatoxin is a contaminant of nuts and grain.