Pervasive Selection for Cooperative Cross-Feeding in Bacterial Communities

Area of Science:

• Microbial Ecology
• Evolutionary Biology
• Systems Biology

Background:

• Bacterial communities exhibit high taxonomic diversity, but the mechanisms maintaining this diversity are not fully understood.
• Metabolic exchange (cross-feeding) is common in bacteria and hypothesized to stabilize genotypic diversity.

Purpose of the Study:

• To investigate if obligate cross-feeding of metabolites can maintain genotypic diversity in bacterial communities.
• To model the impact of intrinsic and extrinsic factors on the evolution of metabolic interactions.

Main Methods:

• Developed a cellular automaton model simulating interactions among six bacterial genotypes.
• Varied parameters such as benefit-to-cost ratio, metabolite diffusion, and environmental amino acid availability.

Main Results:

• Obligate cross-feeding was selected for under diverse conditions, especially in spatially structured environments.
• Cooperative clusters formed, limiting exploitation by non-producers and maintaining diversity.
• Environmental amino acid supplementation disrupted cross-feeding and favored cost-saving auxotrophs.

Conclusions:

• Spatially structured environments and limited nutrient availability promote the evolution of metabolic interactions.
• Cross-feeding is a key mechanism for maintaining genotypic diversity in microbial populations.