Fluorescence microscope studies of Ustilago maydis and Penicillium italicum after treatment with imazalil or fenpropimorph

Abstract

Imazalil and fenpropimorph caused morphological changes in sporidia of Ustilago maydis and in germinating conidia of Penicillium italicum, as observed by fluorescence microscopy using an optical brightener. Sporidia of U. maydis appeared swollen, distorted, multicellular and, sometimes, branched; conidia of P. italicum swelled in size, and extension of the germ tubes was strongly inhibited. Mycelium of P. italicum, treated with fenpropimorph, showed much enlarged hyphal diameters and relatively short distances between septa. Imazalil and fenpropimorph also caused an irregular deposition of β–1,3 and β‐1,4 polysaccharides, probably chitin, in U. maydis and P. italicum. The latter phenomenon is discussed in relation to the following observed effects of fungicides that inhibit ergosterol biosynthesis: differences in effect on the morphology of budding and filamentous fungi; preferential inhibition of yeast‐hypha conversion in dimorphic fungi; disorganisation of septum formation in budding fungi; and inhibition of spheroplast formation from budding fungi.

Importance and Role of Sterols in Fungal Membranes

“…The distribution of chitin is also altered in Aspergillus jumigatus treated for 4 h with 35 ng/ml of itraconazole (Marichal et al 1985;Vanden Bossche et al 1988). Similar effects were observed with the 14-demethylase inhibitor, imazalil, or the LIs _Ll7 isomerase inhibitor, fenpropimorph (Kerkenaar and Barug 1984).…”

Synergistic action of nikkomycin X/Z with azole antifungals on Candida albicans

“…All the above results seem to be inconsistent with previous reports given by many authors who observed irregular distribution of chitin and unbalanced (possibly enhanced) biosynthesis of this polysaccharide as a result of the action of antifungal azoles. The phenomenon was demonstrated by fluorescence microscopy (Kerkenaar & Barug, 1984;Marichal et al, 1984;Vanden Bossche, 1985) and by the determination of the chitin:total carbohydrate ratio (Vanden Bossche, 1985). It should be noted, however, that all these previous observations were made after 24 h treatment of fungal cells with azole derivatives.…”

“…by compounds altering membrane fluidity. Previously azole antifungals were shown to cause the uncoordinated synthesis and irregular distribution of chitin in C. albicans (Vanden Bossche, 1985) and some other fungi (Marichal et al, 1984;Kerkenaar & Barug, 1984). On the Transport studies.…”

Ergosterol Biosynthesis Inhibitors

“…Both imazalil and fen- propimorph also caused an irregular deposition of beta-I,3 and beta-l,4 polysaccharides, probably chitin, in U. maydis and Penicillium italicum [31,32]. This suggests that either the decreased availability of ergosterol results in an uncoordinated synthesis of chitin or that £1 8 (14) -sterols (e.g., ignosterol) and 14-methylsterols perturb both the activity of chitin synthetase.…”

“…It is of interest that fungi, grown in inhibitory concentrations of the 14-demeth y lase inhibitor, imazalil, and of a a 14 -red uctase inhibitor, fenpropimorph, showed the same morphological alterations [31]. Both imazalil and fen- propimorph also caused an irregular deposition of beta-I,3 and beta-l,4 polysaccharides, probably chitin, in U. maydis and Penicillium italicum [31,32].…”