ABSTRACT
This chapter examines sexual agglutination in Hansenula wingei, sex-directed flocculation in fission yeast, sexual agglutination in Saccharomyces cerevisiae, flocculation of brewers' yeast, and cell aggregation in other yeast species. Yeasts are fungi that are conspicuously unicellular for the greater part of their life cycle. Yeasts divide characteristically by budding, although certain ones divide by binary fission. Sexual agglutination in fungi was discovered, together with Hansenula wingei, in 1956 by L. J. Wickerham. Flocculation is obviously of great practical concern to the brewer. The course of fermentation depends on the concentration of active cells in suspension. Similar events and functions are found also in the other yeast aggregation systems. There are other yeast species known definitely to be sexually agglutinative. Among them are Hansenula holstii, Saccharomyces transvaalensis, and Tremella mesenterica. In the complicated series of events that constitute the life cycle of a yeast, cell aggregation may not be the most interesting nor the most conspicuous.
