Complex Ecotype Dynamics Evolve in Response to Fluctuating Resources.

Area of Science:

• Microbial Ecology
• Evolutionary Biology
• Microbial Genetics

Background:

• Microbial populations often face sporadic resource availability, driving ecotypic diversification and cooperation.
• The influence of resource fluctuation patterns on cooperative ecotype emergence remains incompletely understood.

Purpose of the Study:

• To investigate how repeated resource limitation cycles affect ecotype establishment and maintenance in structured environments.
• To determine the impact of 1-day versus 10-day feast/famine cycles on Escherichia coli evolution.

Main Methods:

• Evolving 32 populations of Escherichia coli under distinct feast/famine cycles (1-day vs. 10-day) for 900 days.
• Conducting population-level, genomic, transcriptomic, and phenotypic analyses on evolved clones.
• Utilizing biofilm density, mutational parallelism, mutation rates, and cross-feeding behaviors as key indicators.

Main Results:

• 10-day feast/famine cycles led to increased biofilm density, higher mutational parallelism, and elevated mutation rates compared to 1-day cycles.
• Multiple ecotypes emerged under 10-day cycles, exhibiting cooperative behaviors, including bidirectional cross-feeding.
• Transcriptomic data supported the evolution of bidirectional cross-feeding, consistent with the Black Queen Hypothesis.

Conclusions:

• Repeated, prolonged resource limitation can drive rapid ecotypic diversification and the evolution of mutualistic cooperation in microbial populations.
• This study demonstrates the de novo evolution of Black Queen relationships in a single-ancestor microbial population, providing a model for studying cooperation.
• Findings offer insights into the eco-evolutionary processes underlying the emergence of cooperative relationships in natural microbial communities.