Fine structural investigation of Malassezia furfur: I. Size and shape of the yeast cells and a consideration of their ploidy.

Small and medium sized yeast cells of cylindrical or oval shape predominated in two Malassezia furfur-standard strains CBS 1878 and CBS 6001 during the exponential growth phase. Large cells of wide-oval shape were rare. They were encountered at the beginning of the stationary phase in strain CBS 6001, which also tended to form filaments easily. In the scales of pityriasis versicolor, there were large wide-oval or spherical cells besides small and medium sized yeast cells and hyphal filaments. Considering the variable size and shape of the yeast cells, differences of their ploidy seemed likely, as described in other fungal species. This aspect is supported by the surface/volume quotient.