Genes Required for Ethanol Tolerance and Utilization in Saccharomyces cerevisiae

Abstract

The yeast deletion set was screened to identify mutations impacting ethanol tolerance under limited aeration. Ethanol tolerance was correlated with growth and assessed as the ability to attain the final optical density reached by the parental strain. Of the 4,750 deletants evaluated, 175 strains showed a growth defect in the presence of 5% ethanol. Of these, 21 strains showed a severe growth defect. Growth of many of these strains improved with aeration, but five strains continued to show weak growth: CLC1Δ, GSH1Δ, UME6Δ, TDP3Δ, and VPS24Δ. ADH1Δ also showed higher levels of sensitivity to ethanol but did not grow as well as the other strains in the minimal medium used for the assay in the absence of ethanol and displayed a stronger effect of aeration. The deletion set was also screened to identify mutations affecting growth on ethanol as sole substrate and energy source. Deletants were simultaneously evaluated on lactate to define those mutations needed for growth on respiratory substrates. A total of 176 deletants conferred a growth defect on both ethanol and lactate. Many of these genes are involved in respiration, in mitochondrial ATP synthesis, or define other mitochondrial functions required for organelle integrity. An additional 165 deletants resulted in an ethanol-specific growth defect. These deletants included other mitochondrial proteins as well as genes representing several different functional families. Only 14 genes conferred a specific growth defect on lactate. No deletants were found to confer a growth defect on low sugar concentrations.