Investigating Acid Stress Response in Different<i>Saccharomyces</i>Strains

Abstract

Yeast cells need to respond to a variety of stresses found in such different conditions as gastrointestinal tract after probiotic ingestion or fermentation vat during ethanol production. In the present study, H + neutralisation capacity, membrane fatty acid composition, H + -ATPase activity, and cytosolic Ca 2+ concentration were evaluated in yeast cells used for probiotic ( Saccharomyces boulardii ) and laboratory ( Saccharomyces cerevisiae W303) purposes, as well as in some W303 mutant strains for ENA1 gene and S. cerevisiae BY4741. Results show that the H + internal concentration of yeast is regulated by several systems, including the plasma membrane H + -ATPase, and that Ena1p has an important but undefined role in the cellular response to acid. Membrane fatty acid composition of S. cerevisiae W303 strain was affected by exposure to acidic pH, but the presence of 86 mM NaCl prevented this effect, whereas membrane fatty acid composition of S. boulardii was unaffected by acidic pH. We also demonstrated that the acid stress response is dependent on calcium metabolism and blocked by FK 506.