Microbial expansion-collision dynamics promote cooperation and coexistence on surfaces

Area of Science:

• Microbial Ecology
• Evolutionary Biology
• Population Dynamics

Background:

• Microbial colonies on surfaces exhibit expansion-collision dynamics, leading to genetically diverse boundaries.
• These dynamics create alternating selective pressures: expansion competition and boundary competition, favoring different strategies.

Purpose of the Study:

• To test if expansion-collision dynamics promote the stable coexistence of microbial specialists with different growth strategies.
• To investigate if time-varying, negative frequency-dependent selection maintains diversity in microbial populations.

Main Methods:

• Experimental competition between exoenzyme-secreting 'cooperator' yeast (expansion specialists) and non-secreting 'defector' yeast (boundary specialists).
• Utilized lattice-based spatial simulations to model expansion-collision dynamics and validate experimental findings.

Main Results:

• Cooperator-defector coexistence or cooperator dominance was observed under expansion-collision dynamics.
• Defector dominance occurred in the absence of these dynamics.
• The frequency of cooperators depended on initial colonization density and the cost of cooperation.

Conclusions:

• Expansion-collision dynamics with costly public goods production are sufficient to ensure stable microbial cooperator-defector coexistence.
• This mechanism may be crucial for sustaining cooperation and managing conflict in pioneering microbial species on surfaces.