Apparent nonsolvent water and osmotic behavior of yeast cells

Abstract

1. 1. l-Xylose and dimethylsulfoxide permeate the yeast cell, reaching an intracellular eqiulibrium concentration significantly lower than the medium concentration. At equilibrium the intracellular dimethylsulfoxide concentration is 70–85%, the l-xylose concentration about 40% of that in the medium. In anaerobically grown yeast, lacking intracellular membranous structures, the same equilibrium concentrations are reached as in normal yeast. 2. 2. Both l-xylose and dimethylsulfoxide are present inside the cells in an osmotically active form. 3. 3. The osmotic response of yeast cells in hypertonic NaCl solutions shows a deviation from ideal osmotic behavior. The deviation could be explained by increase of the number of intracellular particles in hypertonic salt solutions and by elasticity forces in the cell wall, causing some reduction of the cellular volume with a connected increase in the intracellular tonicity. 4. 4. With equilibrium dialysis on disintegrated cells, it could be shown that there exists no bound water or exclusion water with respect to l-xylose and dimethylsulfoxide in the yeast cell. 5. 5. The experimental results make the existence of osmotically inactive compartments in the yeast cell, as suggested in recent literature, highly improbable.