Abstract
Commensal microbiota colonize the surface of our bodies. The inside of the gastrointestinal tract is one such surface that provides a habitat for them. The gastrointestinal tract is a long organ system comprising of various parts, and each part possesses various functions. It has been reported that the composition of intestinal luminal metabolites between the small and large intestine are different; however, comprehensive metabolomic and commensal microbiota profiles specific to each part of the gastrointestinal lumen remain obscure. In this study, by using capillary electrophoresis time-of-flight mass spectrometry (CE-TOFMS)-based metabolome and 16S rRNA gene-based microbiome analyses of specific pathogen-free (SPF) and germ-free (GF) murine gastrointestinal luminal profiles, we observed the different roles of commensal microbiota in each part of the gastrointestinal tract involved in carbohydrate metabolism and nutrient production. We found that the concentrations of most amino acids in the SPF small intestine were higher than those in the GF small intestine. Furthermore, sugar alcohols such as mannitol and sorbitol accumulated only in the GF large intestine, but not in the SPF large intestine. On the other hand, pentoses, such as arabinose and xylose, gradually accumulated from the cecum to the colon only in SPF mice, but were undetected in GF mice. Correlation network analysis between the gastrointestinal microbes and metabolites showed that niacin metabolism might be correlated to Methylobacteriaceae. Collectively, commensal microbiota partially affects the gastrointestinal luminal metabolite composition based on their metabolic dynamics, in cooperation with host digestion and absorption.
Highlights
The intestinal microbiota consists of bacteria inhabiting the intestinal tract of mammals
There have been many reports about the functions of intestinal microbiota being related to host diseases such as obesity [2,3], diabetes [4,5,6], atherosclerosis [7,8,9], atopic dermatitis [10,11,12], immune system disorders [13,14], and brain function disorders [15,16,17,18,19]
In the case of C57BL/6 mice fed with normal diet, a large percentage of Lactobacillaceae was observed in the stomach and small intestine, while the large intestinal microbiota is mainly composed of Bacteroidaceae, Prevotellaceae, Rikenellaceae, Lachnospiraceae, and Ruminococcaceae [20]
Summary
The intestinal microbiota consists of bacteria inhabiting the intestinal tract of mammals. They possess various functions, ranging from supporting the digestive function of their host to maintaining a robust immune system in the host [1]. Some studies reported that small and large intestinal metabolome profiles were different, owing to the different composition of gastrointestinal microbiota [21,22]. Metabolome profiling throughout the gastrointestinal tract, and its correlation with gastrointestinal microbiota, is not well understood. A 16S rRNA gene-based gastrointestinal microbiome analysis was conducted
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