Adaptation mechanism of yeast to extreme environments: Construction of salt-tolerance mutants of the yeast Saccharomyces cerevisiae

A salt-tolerant mutant was derived from a haploid yeast, Saccharomyces cerevisiae DKD-5D-H, through repeated mutations with ethyl methanesulfonate. The mutant showed decreased cell size and could grow in the presence of NaCl up to 10%. A similar mutation method was also used to induce salt-tolerance in a diploid yeast, S. cerevisiae Kyokai no. 7. The mutant of the strain showed drastically decreased cell size, almost comparable with that of bacteria, and was resistant to NaCl up to 18%. These two mutation studies on haploid and diploid yeast strains indicated that the salt-tolerance was acquired through the decrease in yeast cell size.