SYNTHESIS OF STERIGMATOCYSTIN ON A CHEMICALLY-DEFINED MEDIUM BY SPECIES OF ASPERGILLUS AND CHAETOMIUM

Sterigmatocystin (ST) is a secondary metabolite and a principal mycoto xin known to be produced by over 30 species of filamentous fungi. It i s also one of the late intermediates in aflatoxin biosynthesis. We hav e tested the ability of 7 species of Aspergillus, including 4 strains of A. versicolor, one species of Bipolaris, and two species of Chaetom ium, to produce ST on a sucrose-salts-phenylalanine defined medium as well as on three complex substrates. Highest ST production in our surv ey was by a strain of A. versicolor grown on wheat, whereas, the highe st ST production on defined medium was by C. cellulolyticum. To our kn owledge, this is the first report of ST production by C. cellulolyticu m on any substrate. In precursor feeding studies, resting cultures of wild type A. nidulans and A. versicolor were unable to biotransform O- methylsterigmatocystin (OMST), the last known intermediate in aflatoxi n biosynthesis. These results suggest that ST is the end product of po lyketide metabolism in the strains tested.