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

Abstract

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 (H₂O₂) stress condition, which we named the lethal concentration of H₂O₂ (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 H₂O₂ 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 H₂O₂, 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.