REGULATION OF INTRACELLULAR OSMOTIC-PRESSURE AND CHANGES IN INTRACELLULAR PROTEINS DURING THE INITIAL-STAGES OF SALT STRESS IN ZYGOSACCHAROMYCES STRAINS EXHIBITING DIFFERENCES IN SALT-TOLERANCE

The accumulation of glycerol and inorganic ions and changes in intracellular proteins in a salt-tolerant yeast, Zygosaccharomyces rouxii, and in a salt-sensitive derivative were examined for 3 h after initiation of salt stress by a high concentration of NaCl. The wild-type strain accumulated high levels of glycerol and inorganic ions in response to an increased concentration of NaCl in the medium. Consequently, the intracellular osmotic pressure in the wild-type strain was regulated at almost the same level as the external osmotic pressure within 2 h after salt stress. In the salt-sensitive strain, no increase in intracellular glycerol was observed in the medium with NaCl, in spite of increases in levels of inorganic ions similar to those in the wild-type strain. The contractibility of cells of the salt-sensitive strain was inferior to that of the wild-type strain in the medium containing NaCl. Levels of various proteins increased or decreased upon salt stress in the wild-type strain and, to a lesser extent, in the salt-sensitive derivative.