Fig. 1. Human-derived microbiota prevent mucus defects in mice fed a Western-style diet (WSD) in a fiber-dependent manner.

HD Habitual diet, HF High-fiber diet, m male, f female. A Selection of participants from a previously published intervention study³², in which participants increased their dietary fiber intake for 12 weeks. Participants (n = 67) were ranked based on their improvement in waist-to-hip ratio, body mass index, free fat mass, cholesterol, triglyceride, and glucose levels (heatmap: rows correspond to individual participants, columns correspond to each metabolic parameter). From the top ten responders, shifts in bacterial composition, based on Bray‒Curtis and weighted UniFrac distance metric, were calculated, and after combination with the metabolic score, 5 participants within the top 6 responders were selected. Statistical significance was determined by the Wilcoxon matched-pairs signed-rank test. B Shift in gut bacteria community structure of the 5 human participants selected as donors for microbiota transplantation before and after HF intervention. C Schematic representation of the human-to-mouse FMT experiment using antibiotic-treated mice. Following the first FMT, mice were fed a standard chow diet or a WSD (n = 8 mice/group). D Mucus growth rate and E mucus thickness of the inner colonic mucus layer. F Colon length. G Absolute quantification of host defense protein/peptide transcripts in distal colon; Statistical significance in D-G was determined by 2-way ANOVA and Tukey’s multiple comparison test within microbiota transplant groups. Data in A and D–G are presented as mean ± SD with p_(adj) < 0.05 (*), p_(adj) < 0.01 (**), p_(adj) < 0.001 (***) and p_(adj) < 0.0001(****) considered statistically significant. All P values are two-sided. Parts of A and C were created with BioRender.com. Source data are provided as a Source Data file.