Carbon dioxide production in wild type and PDC1 mutant Saccharomyces cerevisiae undergoing the Crabtree effect

Abstract

The production of carbon dioxide (CO2) was measured under various glucose concentrations in mutant yeast, Saccharomyces cerevisiae (YLR044) and wild type yeast by the use of respirometers. We investigated the effect of high glucose concentrations on yeast cells— referred to as the Crabtree effect. Three different glucose treatments were tested; the concentration found in the growth medium (0.11 M), the optimal concentration for gas production (0.50 M) and the concentration at which the Crabtree effect takes place (1.00 M). We also determined how much CO2 was produced by the wild type yeast compared to the mutant under high glucose concentrations (≥ 0.50 M). The Crabtree effect was observed in the wild type yeast as 3.4 times less CO2 was made per cell at 1.00 M glucose than at 0.11 M. This effect may be due to an evolutionary adaptation in yeast cells to allow competition with other microorganisms for food. The Crabtree effect was not observed in the mutant yeast even though 1.4 times less CO2 was made per cell at 1.00 M glucose than at 0.11 M because this difference was not statistically significant. The final CO2 concentration for mutant and wild type yeast cells show that there was a greater production of CO2 in wild type as compared to mutant yeast, which is presumed to be the result of the low pyruvate decarboxylase activity in the PDC1 mutants.