MECHANISM FOR SODIUM-BICARBONATE INHIBITION OF TRICHOTHECENE BIOSYNTHESIS IN FUSARIUM-TRICINCTUM

Treatment of Fusarium tricinctum NRRL 13426 cultures with dilute sodiu m bicarbonate resulted in dramatic reductions in the production of tri chothecene mycotoxins, geraniol, and carotenoids. All of these compoun ds are biosynthesized from mevalonic acid (I). In addition, three appa rent mevalonic acid metabolites were found in the bicarbonate-treated cultures at concentrations of several parts per million each. Two of t hese compounds were tentatively identified as 3-methyl-4-oxo-2-penteno ic acid (IV) and its rearrangement product, 4,5-dimethyl-5-hydroxy-2(5 H)-furanone (VI). These results suggest a pH-related inhibition of mev alonate kinase or a pH-related activation of an enzyme that is respons ible, at least in part, far the conversion of mevalonic acid to the pe ntenoic acid or its precursor.