Biofilms promote altruism.

Area of Science:

• Evolutionary biology
• Ecology
• Microbiology
• Thermodynamics

Background:

• The origin of altruism and maintenance of biodiversity are key evolutionary and ecological problems.
• Unicellular organisms face a trade-off between maximizing growth rate and growth yield, rooted in irreversible thermodynamics.
• This trade-off presents an evolutionary choice between rapid growth and efficient resource utilization.

Purpose of the Study:

• To investigate the evolutionary basis of altruism in unicellular organisms.
• To explore the role of cooperation as a fifth niche axis for species coexistence.
• To challenge the prevailing view that growth rate alone determines competitive outcomes.

Main Methods:

• Individual-based model simulations were employed.
• Analysis focused on the influence of spatial structure, specifically in biofilms.
• Comparison was made with traditional chemostat models and experiments.

Main Results:

• Spatial structure, exemplified by biofilms, is crucial for the evolution and persistence of altruistic strategies.
• High growth yield at a low growth rate represents an altruistic strategy benefiting the group.
• Biofilms, unlike enrichment cultures, favor altruists by providing necessary spatial organization.

Conclusions:

• Biofilm structures, including microcolonies and cell shedding, support the evolution of primitive altruism.
• Cooperation should be considered a fundamental axis for understanding species coexistence.
• The study highlights the importance of spatial dynamics in microbial evolution and ecology.