A New Simple Method for Isolating Multistress-Tolerant Semidominant Mutants of Saccharomyces cerevisiae by One-Step Selection under Lethal Hydrogen Peroxide Stress Condition

Tolerance of microorganisms to diverse stresses (i.e., multistress tolerance) is a very useful property with industrial applications. We have developed a simple method for isolating multistress-tolerant semidominant mutants of the budding yeast Saccharomyces cerevisiae by one-step selection under lethal hydrogen peroxide (H(2)O(2)) stress condition, which we named the lethal concentration of H(2)O(2) (LCH) method. This method involves simply isolating colonies after plating of mutagenized S. cerevisiae cells, which are cultivated overnight in liquid media, on agar plates containing a lethal concentration of H(2)O(2) for the wild-type strain. Phenotypic and genetic analyses of the ten strains isolated by this method revealed that two strains exhibiting stress tolerance to H(2)O(2), ethanol, heat shock, salt, organic solvent, freeze-thaw, chronological aging, and high concentrations of glucose possess semidominant and distinct single-gene mutations designated as MLT1-1 (multistress tolerance) and MLT2-1, which are responsible for multistress tolerance. From these results, we expect this method to confer multistress tolerance on industrial yeasts.