Limosilactobacillus reuteri abundance increased in high-tameness mice, elevating oxytocin and enhancing active tameness

Domestication, a multigenerational process, involves genetic and environmental adaptations, with tameness being a key behavioral phenotype. The gut microbiota is increasingly recognized for its influence on host behavior, brain development, and cognition via metabolic and immune pathways. Previous research linking gut microbiota to domestication faced limitations like diet differences and contamination. This study addresses these gaps using a controlled model of wild-derived heterogeneous stock (WHS) mice selectively bred for active tameness, defined as the motivation to approach humans, to explore specific microbial associations.

Researchers utilized wild-derived heterogeneous stock (WHS) mice, which were selectively bred for active tameness over generations, creating two tamed groups and two nonselected control groups. They analyzed the gut microbiota composition of these mice. Subsequently, a pyruvate-secreting L. reuteri strain was administered to nonselected control mice. The primary endpoints included measuring changes in gut microbial abundance, blood oxytocin levels, and assessing behavioral changes related to active tameness using specific behavioral tests like the active tameness test.

While overall taxonomic and functional diversity of the gut microbiota remained largely unchanged, the abundance of Limosilactobacillus reuteri was significantly increased in the selectively bred high-tameness mice compared to nonselected controls. This specific microbial shift correlated with the tameness phenotype. Further investigation involved direct intervention: > Administration of a pyruvate-secreting L. reuteri strain to nonselected mice elevated blood oxytocin levels and enhanced active tameness, demonstrating a causal link between this bacterium and behavioral modulation. This suggests a direct role for L. reuteri in influencing neuroendocrine pathways and social behavior.