Investigations on organic fungicides. X. Pyruvic acid accumulation and its relation to the phenomenon of inversion growth as effected by sodium dimethyldithiocarbamate

1. 1. Sodium dimethyldithiocarbamate (NaDDC) induces spores and mycelium of A. niger and P. italicum to accumulate pyruvic acid in the medium. This accumulation shows a maximum at those NaDDC concentrations which in growth experiments on agar lead to the zone of inversion growth, and decreases rapidly at higher concentrations. 2. 2. With mycelial spheres this phenomenon can be studied more easily than with spores. 3. 3. There is a close correlation between factors leading to pyruvic acid accumulation and to inversion growth in so far as NH4-ions are required for both. 4. 4. Pyruvic acid accumulation is supposed to play an important role in bringing about inversion growth in A. niger, because α-keto acids are strong antagonists of NaDDC for this mould. Thus inversion growth would occur because the fungicide induces the mould spores to accumulate an antagonist. 5. 5. Various arguments are put forward to show that mould metabolism plays a definite role in the establishment of inversion growth and that a purely physico-chemical explanation of this phenomenon is improbable. 6. 6. It is suggested that pyruvic acid accumulation by NaDDC is due to interference of this fungicide with one of the coezymes functioning in pyruvate oxidation