Post-natal co-development of the microbiota and gut barrier function follows different paths in the small and large intestine in piglets.

Gut microbiota and intestinal barrier co-develop after birth, establishing a homeostatic state whereby mucosal cells cohabit with commensal bacteria. We hypothesized that this post-natal co-development follows different timings depending on the intestinal site considered. Jejunal, ileal, and colonic luminal contents and mucosa were sampled in suckling piglets at post-natal day (PND) 0, 2, 7, 14, and 28. Jejunal, ileal, and colonic luminal microbiota (evaluated by 16S DNA sequencing followed by beta-diversity analysis) clustered at PND2 but colonic microbiota diverge afterwards (P < .05). Mucosal permeability, evaluated in Ussing chambers, increased with age in the jejunum and ileum (P < .05) but not the colon. Expression of pattern recognition receptor (PRR) exhibited different patterns (gradual or sharp increase, decrease, or no change with age, P < .05) depending on PRR and intestinal site considered. Principal component analysis of mucosa data revealed clear clustering of colonic samples, irrespective of the age and clustering of jejunal and ileal samples, with gradual changes with age. Correlation analysis highlighted three families correlating with mucosal parameters: Enterobacteriaceae in the jejunum, Peptostreptococcaceae in the ileum, and Micrococcaceae in the colon. In conclusion, small and large intestine display close microbiota composition early in life but distinct mucosal phenotype and follow very different post-natal development.