Application of simultaneous selective pressures slows adaptation.

Area of Science:

• Evolutionary Biology
• Microbiology
• Genetics

Background:

• Beneficial mutations in asexual populations can compete, affecting adaptation rates.
• Simultaneous selective pressures may increase mutation competition, potentially slowing adaptation.

Purpose of the Study:

• To investigate how multiple selective pressures affect the rate of adaptation in Saccharomyces cerevisiae.
• To compare fitness increases under single versus multiple nutrient limitations.

Main Methods:

• Evolved Saccharomyces cerevisiae strains for ~500 generations under one or three limiting nutrient pressures (glucose, histidine, uracil).
• Measured evolved relative fitness using competition assays.
• Utilized high-throughput sequencing to identify mechanisms of fitness changes.

Main Results:

• Populations under single selective pressures showed significant fitness increases.
• Populations under three selective pressures did not show statistically significant fitness increases on any single pressure compared to the ancestral strain.
• Simultaneously limiting three nutrients slowed the rate of evolution on any single pressure relative to single-pressure evolution.

Conclusions:

• Multiple selective pressures can significantly slow the rate of adaptation in yeast.
• This principle may have implications for managing diseases like cancer and infectious diseases by slowing progression and prolonging drug efficacy.