Preparation of Yeast Cells for Staining

Staining yeast cells for the presence and location of antigens is particularly challenging. They are small, making the resolution of any antigen difficult; they have a thick cell wall that antibodies cannot penetrate and that is difficult to remove; and they grow in suspension, making handling difficult. In addition, background problems can be especially severe, particularly with polyclonal antibodies, because many antisera contain antibodies to yeast cell wall components. In this protocol, yeast cells are treated with paraformaldehyde, the cell wall is removed by enzymic digestion, and the spheroplasts are attached to poly-l-lysine-coated slides. After cell lysis, the cells are ready to be stained as per normal. Except in unusual circumstances, the detection reagent should be fluorochrome-labeled.