Changes in the microbiota in different intestinal segments of mice with sepsis

Abstract

Introduction: The small intestine, as the main digestion and absorption site of the gastrointestinal tract, is often overlooked in studies, and the overall microbiota does not reflect the makeup of the microbiota in different segments of the intestine. Therefore, we aimed to exclude the influence of routine ICU treatment measures on sepsis patients and observed changes in the diversity and abundance of gut microbiota in different intestinal segments of septic mice.

Methods: The mice were randomly divided into the CLP6h group and the sham group. The contents of the colon and small intestine of the experimental group and the control group were collected after 6 h.

Results: After CLP, the number and structure of the gut microbiota in the colon changed most obviously, among which Bacteroidetes had the most significant changes. Akkermansia, D.Firmicutes_bacterium_M10_2, Blautia, Bifidobacterium, Lactobacillus, Candidatus_Arthromitus, and Muribaculaceae were changed in the colon. Lactobacillus, Bifidobacterium, Akkermansia, Blautia, Candidatus_Arthromitus, and Lachnospiraceae_NK4A136_group were changed in the small intestine.

Discussion: Our experiment found that there were different numbers of unique and common gut microbiota in the small intestine and colon after sepsis, and the gut microbiota of the colon changed more drastically after sepsis than the small intestine. Thus, we should focus on protective gut microbiota and mucin-degrading microbes. We hope that these results will provide help for sepsis treatment in the future.

Keywords: Akkermansia; Lachnospiraceae_NK4A136_group; Muribaculaceae; gut microbiota; mucin-degrading microbes; sepsis.

Figure 1

Distribution of gut microbiota in the two mouse groups [CLP6h group (n = 10) and the sham group (n = 10)]. (A) The number of unique gut microbiota species in the colon and small intestine in the sham group. (B) The number of unique gut microbiota species in the colon and small intestine in the CLP6h group. (C) The number of unique gut microbiota species in the colon in the sham group and CLP6h. (D) The number of unique gut microbiota species in the small intestine in the sham group and CLP6h. (E) The number of unique gut microbiota for every sample. The cross-section is the number of gut microbiota in common for every sample. (F) A chord diagram of the gut microbiota in the intestine of each sample. The circle diameter indicates the number of points; the greater the number is, the larger the diameter of the circle.

Figure 2

Histogram of gut microbiota distribution in four groups. The abscissa represents the groupings, and the ordinate represents the gut microbiota abundance values. The taxa with an abundance above 1% were selected, and all abundances were in the top 15 for classification.

Figure 3

The dominant gut microbiotas in the different intestinal segments of mice in the sham group and the CLP6h group were characterized by their abundances in a heatmap. Abundance is represented by color depth. The redder the color of the square, the higher the abundance of the strain among the samples.

Figure 4

Changes in the composition of the microbiota in different intestinal segments. (A) Comparison of gut microbiota richness in the small intestine and colon before and after sepsis. (B) Comparison of gut microbiota diversity of the colon and small intestine before and after sepsis. (C) PCoA analysis. The dots with different colors represent different sample groups. The closer the spatial distance of the sample is, the more similar the species composition structure of the sample is.

Figure 5

The OTU PCA and PCoA weighted analysis of the difference in gut microbiota. Weighted UniFrac was included in the calculation on the basis of UniFrac to distinguish differences in species abundance. (A) Species abundance in the small intestine of the sham group and the CLP6h group was significantly different (p = 0.003). (B) Species abundance in the colon of the sham group and the CLP6h group was significantly different. (p = 0.001). (C) In the CLP6h group, the composition of the microbiota in the small intestine and colon was significantly different (p = 0.001). (D) In the sham group, the composition of the microbiota in the small intestine and colon was significantly different (p = 0.001).

Figure 6

Comparison of gut microbiota in different intestinal segments of the two groups. The abscissa represents the abundance values, and the ordinate represents the bacterial groups. The Wilcoxon signed-rank sum test was used. OTU_1, OTU_2, OTU_4, and OTU_9—k: Bacteria, p: Firmicutes, c: Bacilli, o: Lactobacillales, f: Lactobacillaceae, g: Lactobacillus. OTU_5, OTU_12, OTU_15, OTU_11, OTU_14, OTU_13, OTU_29, and OTU_25—k: Bacteria, p: Bacteroidetes, c: Bacteroidia, o: Bacteroidales, f: Muribaculaceae. OTU_10—k: Bacteria, p: Firmicutes, c: Erysipelotrichia, o: Erysipelotrichales, f: Erysipelotrichaceae, g: Dubosiella, s: Firmicutes_bacterium_M10_2. OTU_19, OTU_17, and OTU_27—k: Bacteria, p: Firmicutes, c: Erysipelotrichia, o: Erysipelotrichales, f: Erysipelotrichaceae, g: Allobaculum, s: uncultured_bacterium. OTU_6—k: Bacteria, p: Firmicutes, c: Clostridia, o: Clostridiales, f: Clostridiaceae_1, g: Candidatus_Arthromitus. OTU_8—k: Bacteria, p: Bacteroidetes, c: Bacteroidia, o: Bacteroidales, f: Prevotellaceae, g: Alloprevotella, s: uncultured_Bacteroidales_bacterium. OTU_7—k: Bacteria, p: Verrucomicrobia, c: Verrucomicrobiae, o: Verrucomicrobiales, f: Akkermansiaceae, g: Akkermansia. OTU_37: k: Bacteria, p: Firmicutes, c: Clostridia, o: Clostridiales, f: Lachnospiraceae, g: Lachnospiraceae_NK4A136_group. (A) Comparison of gut microbiota in the small intestine of the sham group and the CLP6h group. (B) Comparison of gut microbiota in the colon of the sham group and the CLP6h group. (C) Comparison of gut microbiota between the small intestine in the sham group and the colon in the sham group. (D) Comparison of gut microbiota between the small intestine of the CLP6h group and the colon of the CLP6h group.

Figure 7

Histological examination of the small intestine and colon. (A) Histological analysis of the small intestine in the sham group. The intestinal mucosal villi were unchanged and normal. (B) Histological analysis of the small intestine in the CLP6h group. The intestinal mucosal villi were sparse and irregular, and the villi became short and broken, with reduced mucosal layer glands and infiltration of inflammatory cells in the muscularis in the CLP6h group. (C) Histological analysis of the colon in the sham group. The intestinal mucosal villi were unchanged and normal. (D) Histological analysis of the colon in the CLP6h group. The intestinal mucosal villi were sparse and irregular, and the villi became short and broken, with vacuolization at the top, reduced mucosal layer glands, and infiltration of inflammatory cells in the muscularis in the CLP6h group.