Morphological organization of glycoprotein containing cell surface structures in yeast

Yeast cells (Schizosaccaromyces pombe and Saccharomyces cerevisiae) that are rapidly cryofixed without cryoprotectants reveal hair-like structures, called fimbriae, on their surfaces. The anchorage point of S. pombe fimbriae can be located either very close to the plasma membrane or in a more peripheral cell wall layer. They can de detached with aqueous ethanol, and biochemical and immunological data indicate that glycoproteins including acid phosphatase constitute a major component of the fimbriae. Mutants of S. cerevisiae lacking the outer heterogeneous mannose chains reveal an altered cell surface morphology. Typical fimbriae are absent. In cells of S. pombe that just have divided, fimbriae are not visible on the newly generated wall. This suggests that fimbriae assembly occurs after division has taken place. Fimbriae seem to be involved in the cell-cell recognition and/or aggregation process.