[Mechanism of action of terrazol].

Higher concentrations of terrazol inhibit the growth of a large number of fungi, but oomycetes are most sensitive. At medium concentrations (ED50 = 10 ppm) in Mucor mucedor several alterations of ultrastructure are recognizable even after short incubation periods. Significant observations are vacuolization of the mitochondrial cristae, invagination of the cytoplasmic membrane, and thickening of the cell wall. Later on, numerous vacuoles in the cytoplasm are visible. Primary effects on the cell membrane (destructive effect), on O2-consumption, on fermentation, or on nucleic acid synthesis could not be demonstrated. Lipid synthesis under the influence of terrazol showed characteristic changes. The synthesis of triglycerides and sterolesters was inhibited while the synthesis of free fatty acids and phospholipids was stimulated. Addition of lipids, vitamines, amino acids, or nucleic acids did not counteract the effect of terrazol. Further investigations are necessary to elucidate the primary mechanism of action.