Effect of cryo-protective agents on the growth and ultrastructure of Saccharomyces cerevisiae

When suspended in a glucose medium supplemented with varying amounts of DMSO, ethylene glycol, glycerol, lactose and sodium chloride at its optimum temperature of 30 degrees C, a diploid strain of Saccharomyces cerevisiae gave a mean generation time inversely proportional to the increased concentrations of these anti-freeze compounds. No growth was attained at 0 degrees C and -5 degrees C, and mixtures of the compounds did not support any growth even at 30 degrees C. At 0 degrees C and -5 degrees C with increasing percentages of the individual compounds, and at 30 degrees C, 0 degrees C and -5 degrees C, with mixtures of the compounds, a significant decrease in survival was obtained. As compared to cells grown in the absence of antifreeze compounds, electron microscopy of the cells which grew at 30 degrees C in the presence of antifreeze compounds showed thicker cell walls, highly convoluted plasmalemma, vacuoles filled with electron-dense fibrous material, spherosomes, poorly developed mitochondria and many vesicles.