Molecular and physiological aspects of aflatoxin and sterigmatocystin biosynthesis by Aspergillus tamarii and A-ochraceoroseus

Until recently, only three species (Aspergillus flavus, A, parasiticus and A. nomius) have been widely recognized as producers of aflatoxin. In this s tudy we examine aflatoxin production by two other species, A. tamarii and A . ochraceoroseus, the latter of which also produces sterigmatocystin. Toxin -producing strains of A. tamar ii and A. ochraceoroseus were examined morph ologically, and toxin production was assayed on different media at differen t pH levers using thin layer chromatography and a densitometer. Genomic DNA of these two species was probed with known aflatoxin and sterigmatocystin biosynthesis genes from A. flavus, A. parasiticus and A. nidulans. Under th e high stringency conditions, A. tamarii DNA hybridized to all four of the A. flavus and ii. parasiticus gene probes, indicating strong similarities i n the biosynthetic pathway genes of these three species. The A. ochraceoros eus DNA hybridized weakly to the A. flavus and A. parasiticus verB gene pro be, and to two of the three A. nidulans probes. These data indicate that, a t the DNA level, the aflatoxin and sterigmatocystin biosynthetic pathway ge nes for A. ochracearoseus are somewhat different from known pathway genes.