Lm. reuteri improved physiological responses (NLRP3 inflammasome, HPA axis, and intestinal mucosal barrier) and gut microbiota dysbiosis in chronically stressed mice (n = 6/group). RT-qPCR of hippocampal (a) NLRP3, (b) Caspase-1, and (c) ASC mRNA normalized to expression of GAPDH. The hypothalamic–pituitary–adrenal axis index of (d) CRH and (e) CORT. RT-qPCR of (f) colonic ZO-1 mRNA and (g) occludin, normalized to expression of GAPDH. (h) Immunohistochemistry of intestinal tissue based on ZO-1 and occludin protein in WAS mice. (i,j) Chao1 index and Shannon index of fecal microbiota in SD mice. (k) Microbial taxa at the phylum level in SD mice. (l) The top 15 microbial taxonomic groups at the genus level in SD mice. (m) Distribution histogram based on LDA (LDA > 2) in SD mice. (n,o) Chao1 index and Shannon index of fecal microbiota in WAS mice. (p) Microbial taxa at the phylum level in WAS mice. (q) The top 15 microbial taxonomic groups at the genus level in WAS mice. (r) Distribution histogram based on LDA (LDA > 2) in WAS mice. Statistics: ns: not significant (p > 0.05), * p < 0.05, ** p < 0.01, *** p < 0.001.