Effect of ethionine on tropolone biosynthesis in Penicillium stipitatum

Abstract

l-Ethionine (tested at 0.26, 0.52 and 1.04 m M) was found to be a potent inhibitor of tropolone biosynthesis in Penicillium stipitatum. The effect of d-ethionine was identical to that of the l-enantiomorph. Although cell synthesis was always diminished in the presence of ethionine, the effect on tropolone formation was much greater than could be accounted for by this fact alone. Neither the simultaneous addition of equimolar amounts of methionine nor pretreatment with methionine prevented the ethionine inhibition. Sulfanilamide (0.50 and 1.00 m M), succinylsulfathiazole (0.23 m M), and dl-methionine sulfoxide (0.13, 0.26, and 0.52 m M) had no significant effect on tropolone biosynthesis. From ethioninetreated P. stipitatum cultures, a sample of pure, crystalline orsellinic acid was isolated by partition and paper chromatographic techniques. Methods for the detection of orsellinic acid were supplemented by the use of gas liquid chromatography. Orsellinic acid had a retention time of 10.5 minutes on 3% nitrile silicone columns at 194 °C. Orsellinic acid was also identified in extracts of the culture fluids of the following molds by paper chromatographic methods: Chaetomium globosum, Cladosporium fulvum, Curvularia lunata, Gibberetta fujikuroi, and Penicillium cyclopium. No evidence for the presence of orsellinic acid was obtained in uninhibited cultures of Penicillium stipitatum, Gliocladium roseum, Aspergillus quadrilineatus, and a Cephalosporium sp.