Beneficial Mutations from Evolution Experiments Increase Rates of Growth and Fermentation
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A major goal of evolutionary biology is to understand how beneficial mutations translate into increased fitness. Here, we study beneficial mutations that arise in experimental populations of yeast evolved in glucose-rich media. We find that fitness increases are caused by enhanced maximum growth rate (R) that come at the cost of reduced yield (K). We show that for some of these mutants, high R coincides with higher rates of ethanol secretion, suggesting that higher growth rates are due to an increased preference to utilize glucose through the fermentation pathway, instead of respiration. We examine the performance of mutants across gradients of glucose and nitrogen concentrations and show that the preference for fermentation over respiration is influenced by the availability of glucose and nitrogen. Overall, our data show that selection for high growth rates can lead to an enhanced Crabtree phenotype by the way of beneficial mutations that permit aerobic fermentation at a greater range of glucose concentrations.
KeywordsBeneficial mutations Fitness effects Experimental evolution Yeast Crabtree Trade-off
MJM conceived the study. ALS, MEM, DJM, and MJM designed the study. ALS and MJM conducted experiments. MEM and MJM analyzed the data. ALS, MEM, DJM, and MJM wrote the paper.
MJM was supported by ARC Grant No. FT170100441.
Compliance with Ethical Standards
Conflict of interest
We have no competing interests.
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