Structure of foam and film forming cells of Saccharomyces cerevisiae

Characteristics were described of the foam and film forming strains of Saccharomyces cerevisiae. These strains show a thin proteic layer at the cell surface that is absent in common non-foam and non-film forming strains. In young cells the proteic layer is not visible under a Scanning Electronic Microscope. The proteic layer becomes visible in old cells of foam forming strains because their surface becomes rough after collapse and contraction of the wall. In film forming cells, the proteic layer is rigid and preserves the original shape of the cells in the form of a blister after contraction of the wall. The strict correlation between these cell wall traits and capacity of forming foam and film were confirmed also by tetrad analysis of the hybrids obtained by crossing of segregants of these two types of strains.