ULTRASTRUCTURAL FEATURES OF THE DIMORPHIC YEAST MALASSEZIA-FURFUR

Purpose. The ultrastructure of the dimorphic yeast species Malassezia furfur was investigated by transmission electron microscopy. Materials and methods. Yeast-mycelial conversion of the strain CBS 7019 was obtained at 32 degrees C on Lawenstein-Jensen medium supplemented with 1 % olive oil. Cells were fixed with 1.5 % aqueous KMnO4, post-fixed with 1 % OsO4 and stained with uranyl acetate. Results and discussion. Both yeasts and filaments exhibited the thick and multilamellar cell wall typical of basidiomycetous fungi. In contrast, the cell wall was confirmed to be crossed by an electron-translucent band facing a helicoidal invagination of the plasma membrane, unique to our knowledge in the world of fungi. M. furfur was able to form true septate branching hyphae. The thick cross wails appeared composed of fibrillar material with no pore or micropore-like structures. These unfunctional septa recalled similar features described in Entyloma nymphaene, Trichosporon pullulans and few Ustilaginales. A phenomenon of endosporulation was also observed.