Bacillus subtilis modifies scatter-hoarding behavior by regulating gut Akkermansia muciniphila-mediated spatial memory in squirrels

The gut-brain axis mediates communication between the gut microbiota and cognitive function, but its role in complex, ecologically relevant behaviors remains poorly understood. Here, we demonstrate that the probiotic Bacillus subtilis enhances scatter-hoarding—a spatial memory-dependent foraging behavior—in rodents by acting as an ecological engineer of the gut microbiome. Supplementation with B. subtilis in Pallas’ squirrels (Callosciurus erythraeus) significantly increased scatter-hoarding intensity, an effect associated with a marked enrichment of the gut commensal Akkermansia muciniphila. This microbial shift elevated cecal levels of short-chain fatty acids, including hexanoate, and increased serum tryptophan. In the mouse model, direct A. muciniphila oral gavage improved spatial memory and activated hippocampal pathways for synaptic plasticity, such as long-term potentiation and glutamatergic signaling. Our findings reveal a novel gut-brain pathway wherein B. subtilis promotes cognitive performance via A. muciniphila, suggesting that microbiome-mediated enhancement of spatial memory may underlie adaptive foraging strategies in wild rodents, with potential implications for cognitive health and probiotic therapeutics.