Yeast Spontaneous Mutation Rate and Spectrum Vary with Environment

Area of Science:

• Evolutionary biology
• Genetics
• Microbiology

Background:

• Mutation is the primary driver of evolution and biodiversity.
• Environmental impacts on mutation rate and spectrum are poorly understood, especially under conditions that permit growth.

Purpose of the Study:

• To quantify mutation rate and spectrum in Saccharomyces cerevisiae across seven distinct environments.
• To investigate the influence of environmental conditions on various mutation types and their implications for evolutionary inferences.

Main Methods:

• Whole-genome sequencing of yeast following mutation accumulation.
• Comparison of mutation rates and spectra across environments with varying growth rates and cell viability.

Main Results:

• Nuclear mutation rate per generation varied 3.6-fold, increasing with slower growth.
• Mutation rate per year was more constant across environments than per generation.
• Significant variations in mutation spectrum, including transition/transversion ratio and AT bias, were observed.
• Other mutation types (indels, duplications, chromosome abnormalities) increased in slower-growing environments.
• Yeast mitochondrial mutation rate increased with growth rate, supporting the metabolic rate hypothesis.

Conclusions:

• Environmental changes influence both the rate and type of mutations, affecting evolutionary trajectories.
• Current evolutionary inferences may be misleading if environmental impacts on mutation are ignored.
• Environmental factors play a dual role in evolution by modulating mutation supply and directing natural selection.