The type VI secretion system governs strain maintenance in a wild mammalian gut microbiome.

The T6SS on an ICE enables Bacteroides to maintain strain stability in a wild mammalian gut microbiome, with 20% of related species harboring this system.

• Why it matters: Understanding how bacterial strains persist in complex gut communities is crucial for insights into microbiome stability and health, yet the mechanisms remain unclear.
• What they did: Researchers developed genetic tools and used a community replacement strategy to show that B. acidifaciens employs T6SS to antagonize co-residents, affecting long-term strain maintenance.
• The result: Loss of T6SS impairs strain persistence without affecting initial colonization, and transfer of T6SS-ICE provides transient benefits but can lead to population decline, highlighting context-dependent stability.