Enhancement of K-strategy evolution in histidine utilization using a container with compartments

Area of Science:

• Evolutionary biology
• Microbial evolution
• Population dynamics

Background:

• Evolutionary strategies are classified as r-strategy (increased growth rate) or K-strategy (increased carrying capacity).
• Spatial structures are known to induce K-strategy evolution.
• Previous studies showed E. coli could evolve K-strategy without spatial structures under glucose limitation, but this was not tested for other resources.

Purpose of the Study:

• To investigate if spatial structures are necessary for K-strategy evolution in histidine utilization by Escherichia coli.
• To determine the role of spatial structures in directing bacterial evolution towards higher carrying capacity under nutrient limitation.

Main Methods:

• Established a simplified evolution experiment using histidine-requiring E. coli.
• Grew bacteria in a container with compartments under histidine limitation.
• Performed whole genome sequencing on K-adapted strains.

Main Results:

• Confirmed the importance of spatial structures in driving K-strategy evolution for histidine utilization.
• Identified a functional variety of mutated genes during the fitness-increasing period in K-adapted strains.
• Demonstrated that spatial structures are key for evolving higher carrying capacity in this context.

Conclusions:

• Spatial structures are essential for inducing K-strategy evolution in histidine utilization.
• The observed limitations in K-strategy evolution for certain nutrients may stem from a lack of appropriate selection, not a scarcity of causal mutations.
• This highlights the critical role of environmental architecture in shaping evolutionary trajectories.