Figure 1 Study design. N: Pseudo-aseptic group; K: Blank group; A: Microbiota^- colitis group; F: Blank group; G: Microbiota⁺ colitis group; DSS: Dextran sulfate sodium; GC-MS: Gas chromatography-mass spectrometry.

Figure 2 The combination of five antibiotics could effectively build an intestinal pseudo-aseptic mouse model. A: Antibiotics applied; B: Body weight; C: Operational taxonomic unit counts; D: Microbiota structure; E: Shannon index of alpha-diversity; F: Rank abundance of alpha-diversity; G: Beta-diversity. N: Pseudo-aseptic with antibiotics group; K: Blank group. Compared with the blank group, ^aP < 0.01, ^bP < 0.05.

Figure 3 Mice with bacteria were more severely ill in dextran sulfate sodium-induced colitis. A: Disease activity index score; B: Colon length; C: Colon photos; D: Colon weight; E: Histological lesions score; F: Hematoxylin-eosin staining. A: Microbiota^- colitis group, F: Blank group, G: Microbiota⁺ colitis group. DAI: Disease activity index. Compared with the blank group, ^aP < 0.01, ^bP < 0.05. Compared with microbiota⁺ colitis group, ^cP < 0.01, ^dP < 0.05.

Figure 4 Intestinal mucus loss was more pronounced in dextran sulfate sodium-induced colitis mice with bacteria. A: Alcian blue staining; B: Percentage of positively stained areas; C: Percentage of MUC2-positive stained areas; D: Mucin2 (MUC2) immunofluorescence staining. A: Microbiota^- colitis group, F: Blank group, G: Microbiota⁺ colitis group. MUC2: Mucin2. Compared with the blank group, ^aP < 0.01. Compared with the microbiota⁺ colitis group, ^dP < 0.05.

Figure 5 Analysis of different characteristic microbiota in dextran sulfate sodium-induced colitis mice. A: Operational taxonomic unit counts; B: Goods coverage index dilution curve; C: Specaccum species accumulation curve; D: Observed species violin graph of alpha-diversity; E: Beta-diversity; F: Heat map cluster analysis of 50 different species at the genus level; G: Heat map cluster analysis of Phylogenetic Investigation of Communities by Reconstruction of Unobserved States analysis with Kyoto Encyclopedia of Genes and Genomes pathways at the phylum level. F: Blank group; G: Microbiota⁺ colitis group. Compared with the blank group, ^bP < 0.01.

Figure 6 Analysis of different microbiota metabolites in dextran sulfate sodium-induced colitis mice. A: Orthogonal partial least-squares discrimination analysis; B: Metabolite volcano plot; C: Clustered heat map of significantly expressed metabolites; D: Bubble mapping of the top 20 significant Kyoto Encyclopedia of Genes and Genomes pathways of metabolites; E: Correlation matrix analysis with significant metabolites; F: Correlation matrix of the top 20 differential metabolites and the microbiota at the genus levels. F: Blank group; G: Microbiota⁺ colitis group.