Dynamics of Pusmalemmal Invagination in the Synchronized Cells of Saccharomyces Cerevisiae

Abstract

Plasmalemma of Saccharomyces cerevisiae invaginates inside the cytoplasm. A double aldehyde fixation technique gave a superior preservation of membrane material compared to that obtained by other procedures.Stationary phase equal size single cells of Saccharomyces cerevisiae strain 1829 were separated by gravity sedimentation at 4°C on a 0.5, 1.0, 2.0 M discontinuous sorbitol density gradient. The separated cells were washed free of sorbitol and were grown in 1% yeast extract and 1% glucose. Counting under phase microscope showed that the cells were synchronized for 2-3 generations with a generation time of approximately 2 hr. At different time intervals of growth, cells were washed and fixed in a mixture of paraformaldehyde (2%) and gluteraldehyde (2.5%) in 0.1 M phosphate buffer pH 7.0 for 30 min. These cells were fixed in 1% OSO4 in veronal-acetate buffer pH 6.1 for 15 hr and treated with 0.5% uranyl acetate for 2 hr and further embedded in Epon after dehydration. Thin sections were stained in lead citrate for 30 min.