Gut bacteria may influence social behavior through smell

Phys.org • March 30, 2026 • science

Key Points:

Northwestern University neurobiologists discovered that gut bacteria produce a pungent odor, trimethylamine (TMA), which mice detect through the TAAR5 receptor in their noses, influencing social behaviors such as aggression and hierarchy formation.
The study found that dominant male mice produce TMA due to testosterone suppressing its liver neutralization, and detecting this odor triggers fights among males while subordinate mice display defensive behaviors, establishing social hierarchies.
Disabling the TAAR5 receptor or blocking gut bacteria from producing TMA reduced aggression and destabilized social hierarchies, showing a direct link between gut microbes, olfactory detection, and social behavior.
This research reveals a complete pathway from gut microbiome to behavior via smell and suggests potential implications for understanding how microbe-produced odors might influence social interactions in other species, including humans.
The study, published in Current Biology, highlights that humans also possess the TAAR5 receptor, raising questions about the role of microbiome-derived odors in human social behavior and sensory processing.

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