Sexual co-flocculation and asexual self-flocculation in budding and fission yeasts: experimental establishment of a fundamental difference

Heavily flocculated yeasts were resuspended in a variety of sugar syrups and solutions. Asexual Saccharomyces floes remained patent in water and in 50% galactose but dispersed in 50% mannose and in 10 mM EDTA. Asexual Schizosaccharomyces floes (either h − or h + ) remained patent in water and in 50% mannose but dispersed in 50% galactose and 10 mM EDTA. Sexual Schizosaccharomyces floes (homothallic NCYC 132, or heterothallic h − and h + combined) remained patent in water, in 50% galactose, in 50% mannose, and in 10 mM EDTA. Dispersal of asexual floes in sugar syrups and EDTA suggests that asexual flocculation is mediated by protein–carbohydrate lectinlike interactions stabilized by Ca 2+ . Failure of the sexually flocculent fission yeasts to disperse in any of these diagnostic solutions suggests that sexual flocculation is mediated by protein–protein interactions in which Ca 2+ is irrelevant.