Changes in growth rate of wild-type and PDC1 mutant Saccharomyces cerevisiae in response to caffeine

Larissa Goh, Cindy X. Hu, Sophia Hu, Madeleine Tsoi


Saccharomyces cerevisiae is one of the most studied organisms and can provide vital insight into human physiology. With caffeine the most common drug used by humans, the objective of this experiment was to study how varying caffeine concentrations affected the cell counts of wild-type and mutant strains of S. cerevisiae over time. We prepared three treatments of caffeine concentrations: 100 mM, 150 mM, and 0 mM with three replicates for each treatment. The response of average cell growth rate was measured from 0 to 6 hours of incubation by counting the number of cells using a haemocytometer. We found a significant difference in growth rate between the wild-type and mutant strains of S. cerevisiae using a two-way ANOVA test (p=0.030). This is attributed to the deletion of the PDC1 gene in the mutant, resulting in decreased cell growth due to impaired glucose fermentation. Furthermore, there was a significant difference in the growth rate of S. cerevisiae at different caffeine concentrations (p=2.5x10-6). There was also a significant difference between the caffeine effect on wild-type compared to its effect on mutant S. cerevisiae (p=0.0099). We interpret this to be a result of the mutant already functioning with less pyruvate decarboxylase enzyme, so it will be less affected by the presence of caffeine. From our data, we can therefore conclude that mutant S. cerevisiae has greater resistance to caffeine than wild-type S. cerevisiae.

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