Phenotypic plasticity as an adaptation to a functional trade-off

Area of Science:

• Evolutionary Biology
• Microbial Ecology
• Molecular Biology

Background:

• Organisms face trade-offs, such as allocating resources between growth and motility.
• Escherichia coli exhibits a known trade-off between rapid growth and efficient chemotaxis.
• Phenotypic plasticity can potentially mitigate such evolutionary constraints.

Purpose of the Study:

• To investigate the evolution of phenotypic plasticity in Escherichia coli under cyclical resource availability and motility selection.
• To understand how behavioral adaptations can overcome inherent biological trade-offs.
• To identify the genetic basis of evolved plastic behavior.

Main Methods:

• Propagating Escherichia coli cultures in a cyclical environment alternating between growth and chemotaxis selection.
• Monitoring changes in cell growth rates and motility.
• Genetic analysis to identify mutations responsible for the observed behavioral shift, focusing on the FliA protein.

Main Results:

• Initial adaptation led to increased swimming speed at the cost of growth.
• Subsequent evolution resulted in a plastic behavior: reduced individual cell motility during growth phases and increased proportion of motile cells near carrying capacity.
• A single amino acid change in the FliA protein was identified as the cause of this adaptive plasticity.

Conclusions:

• Phenotypic plasticity can evolve to circumvent fundamental resource allocation trade-offs.
• The evolved behavioral strategy in Escherichia coli allows for optimized resource use across different environmental conditions.
• This study demonstrates how phenotypic plasticity enhances evolvability by expanding accessible adaptive landscapes.