Mutational hotspots lead to robust but suboptimal adaptive outcomes in certain environments

Area of Science:

• Evolutionary biology
• Microbial evolution
• Genetics

Background:

• Adaptive evolution is influenced by mutational biases and environmental factors.
• Mutational hotspots can facilitate rapid access to beneficial mutations.
• Environmental complexity can alter the fitness landscape and observed adaptive outcomes.

Purpose of the Study:

• To investigate how nutrient environments impact the evolution of motility in Pseudomonas fluorescens.
• To compare the role of a mutational hotspot versus no hotspot in adaptation under different conditions.
• To understand how environmental factors shape the mutational spectrum and phenotype strength.

Main Methods:

• Evolving hotspot and non-hotspot strains of Pseudomonas fluorescens Pf0-2x for motility.
• Utilizing nutrient-rich (LB) and nutrient-limiting (M9) media.
• Conducting competition experiments to assess fitness advantages.

Main Results:

• The hotspot strain evolved faster and showed a robust mutational spectrum across environments.
• The non-hotspot strain exhibited environment-dependent mutational spectra.
• Alternative adaptive mutations in nutrient-limited conditions often yielded superior swimmers compared to the hotspot mutation.

Conclusions:

• Mutational hotspots accelerate adaptation but may restrict access to potentially stronger phenotypes.
• Environmental conditions are critical in defining the mutational landscape and the strength of adaptive phenotypes.
• Balancing rapid adaptation with exploration of the mutational landscape is key in evolutionary processes.