Observations on budding cells of Torulopsis glabrata

Abstract

The diminutive pathogenic yeast Torulopsis glabrata was studied by light and electron microscopy, with special attention to the budding process. Polysaccharides were also extracted to determine glycogen in cytoplasmic particles. Elliptical single cells, with a mean volume of 13 μm3, possess ultrastructural features common in other yeasts, viz. nucleus with double membrane and pores, nucleolus, endoplasmic reticulum, mitochondria, vacuoles, lipid bodies, ribosomes, tripartite plasma membrane, and fibrillar wall with outer electron-dense layer. Numerous pocket-like invaginations of varying size and orientation are formed by the plasma membrane. Buds seem to be preceded by an elaboration of such invaginations and by tubular profiles of the endoplasmic reticulum present in the area of the emerging bud. As the bud protrudes, it appears bounded by a layer of newly synthesized wall material. In general, this process is similar to that in other yeasts (e.g., Saccharomyces) but no vesicles were observed in the peripheral cytoplasm of the mother cell during the initial stages of budding. Various stages in the budding cycle are illustrated.