Herd immunity underlies homologous recombination in stationary phase bacteria.

Herd immunity in stationary phase Escherichia coli promotes homologous recombination by enabling phages to act as genetic pollinators, increasing gene flow up to 100-fold.

• Why it matters: Understanding how bacteria sustain high rates of homologous recombination is crucial for insights into their evolution and adaptability, especially since they lack meiotic processes.
• What they did: The study used an E. coli-P1 phage model to demonstrate that herd immunity maintains phage populations and facilitates recombination during stationary phase, requiring recA, recB, and recG genes.
• The result: This reveals that bacterial immune responses can regulate genetic exchange, enabling high recombination rates even when mutation supply is limited, thus shaping molecular evolution.