Experimental evolution reveals genetic routes for adaptive loss of the antibacterial type VI secretion system.

Experimental evolution shows that approximately 90% of Escherichia coli clones lose or weaken their T6SS after 640 generations when competing with T6SS-immune bacteria.

• Why it matters: Understanding how bacteria adapt to lose costly systems like T6SS helps clarify the evolutionary pressures that shape bacterial genomes and their competitive strategies, especially in environments lacking direct interbacterial conflict.
• What they did: The study used experimental evolution and whole-genome sequencing to track T6SS fate in E. coli during competition with T6SS-susceptible or immune strains, revealing mutations in key regulatory and structural genes.
• The result: Findings demonstrate that T6SS can be selectively lost or attenuated through diverse mutations, and identify conserved regulatory elements, providing insights into bacterial adaptation and T6SS regulation.