Higher concentrations of terrazol inhibit the growth of a large number of fungi, but oomycetes are most sensitive. At medium concentrations (ED,, = 10 ppm) in Nucor mucedo several alterations of ultrastructure are recognizable even after short incubation periods. Significant observations are vacuolization of the mitochondria1 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 0,-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 t o elucidate the primary mechanism of action.

It is assumed that the fungistatic effect of terrazol in Mucor mucedo is induced by a liberation of phospholipases within the mitochondria and perhaps at other membranes. In isolated mitochondria a rapid formation of lysolecithin can be demonstrated at low concentrations of terrezol. This would explain the lytic symptoms in mitochondria visible by electron microscopy. Lipid peroxidation could not be demonstrated. The only antidots a t present known for the growth inhibiting effect of terrazol and on its ultrastructural effects are impure saccharose, which seems to contain an unknown factor, and procain hydrochloride or to a lesser extent lidocain, which are wellknown inhibitors of phospholipases. The pathologigal thickening of the cell wall induced by terrazol seems to be an unspecific side effect reflecting a diminished phosphorylating activity of the mitochondria. Uber einige Effekte von Terrazol, einem systeniischen Fungicid, auf Wachstuni, physiologische Aktivitaten so wie auf die Ultrastruktur von Mucor mucedo wurde von LYR et al. (1975) berichtet. Die geniessenen physiologischen Effekte beziiglich Pernieabilitat, At mung, Garung, Nucleinsauresynthese und Lipidsynthesen zeigten jedoch keine so eindeutige Blockierung, da13 man bereits auf eine Priniarwirkung schlienen kannte. Durch Zusatze von Lipiden, Vitaminen, Aniinosauren oder Nucleinsauren lie13 sich die durch Terrazol verursachte Wachstuniheniinung nicht aufheben. Mit Hilfe der Elektronenmikroskopie (CASFERSON u. LYR 1975) konnten aber typische Strukturveranderungen durch Terrazol sichtbar gemacht werden, die vor allem in einer Lysis der inneren Mitochondrieninemhran und einer anschliefienden Vakuolisierung der Mitochondrien bestehen. Daruber hinaus zeigt das Plasnialemma ein Abliisen von der Zellwand und Bildung von pinocytoseartigen Invaginationen. Die Zellwand wird in Ab-

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.

It is assumed that the fungistatic effect of terrazol in Mucor mucedo is induced by a liberation of phospholipases within within the mitochondria and perhaps at other membranes. In isolated mitochondria a rapid formation of lysolecithin can be demonstrated at low concentrations of terrazol. This would explain the lytic symptoms in mitochondria visible by electron microscopy. Lipid peroxidation could not be demonstrated. The only antidots at present known for the growth inhibiting effect of terrazol and on its ultrastructural effects are impure saccharose, which seems to contain an unknown factor, and procain hydrochloride or to a lesser extent lidocain, which are well-known inhibitors of phospholipases. The pathological thickening of the cell wall induced by terazol seems to be an unspecific side effect reflecting a diminished phosphorylating activity of the mitochondria.