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

The T6SS on an ICE is essential for long-term strain maintenance in a wild mouse gut microbiome, with its loss reducing B. acidifaciens persistence.

• Why it matters: Understanding how bacterial strains persist in complex gut communities is crucial for insights into microbiome stability and function, yet the mechanisms remain unclear.
• What they did: Researchers used genetic tools and a strain replacement strategy to show that B. acidifaciens employs a T6SS to antagonize co-residents, and that T6SS loss impairs its long-term presence.
• The result: The T6SS-ICE is shared among species and transfer can temporarily boost colonization but may lead to population decline, indicating context-dependent stabilization of strains.