Vol. 3, Issue 1 (2018)
A study on morphology and membrane ultrastructure of lipid mutant of S. cerevisiae under hypertonic conditions
Author(s): Kanika Sachdeva
Abstract: Saccharomyces cerevisiae is a characteristic eukaryote with membranous organelles, as well as the lipids that form its membranes. Since principles of osmoadaptation are conserved across eukaryotes, yeasts are ideal model systems with which to study the protective role played by membranes. A wild type strain of S. cerevisiae and its lipid mutant defective in the synthesis of phosphatidylcholine and phosphatidylethanolamine, have been used in this study. Cells were tested for viability with colony count method as well as through EM following salt treatment. In wild type cells the cell surface is quite smooth. In comparison, the mutant cells show wrinkled surface. This shows that lipids have some important role in cell wall biogenesis also. Mutant cells seem to be more rounded as compared to the typical ovoid nature of wild type cells. Change in the shape may be due to the cytosolic disruption indirectly or directly due to phospholipid changes; because cytosolic proteins are known to be interacting with phospholipids especially negatively charged lipids. EM studies show that cell wall is more sensitive to salt in mutant cells. Not only plasma membrane but cell wall is also affected, leading to more lysis in the mutant strain. The loss of viability of S. cerevisiae after hypertonic stress superimposes the fact that plasma membrane is the primary site of osmotic injury.