Fungal fimbriae. III. The effect on flocculation in Saccharomyces.

Flocculent strains of Saccharomyces cerevisiae and S. carlsbergensis (S. uvarum) produced many short (0.5 mum) hairs (fimbriae) on the outer cell walls. Non-flocculent strains produce few fimbriae. Cells that are flocculent in wort but not in defined medium produce fimbriae only in the former medium. Cells treated with pronase lose both their fimbriae and the ability to flocculate. Cells treated with alpha-amylase retain some fimbriae but lose the ability to flocculate. It is suggested that the fimbriae may be the surface mannan-protein complexes known to be involved in flocculation and also in protein secretion. Haploid cells of both mating types also produced fimbriae, some of which apparently have a terminal knob.