The Differences between Luminal Microbiota and Mucosal Microbiota in Mice

The differences between luminal microbiota (LM) and mucosal microbiota (MAM) were little known, especially in duodenum. In this study, LM and MAM in colon and duodenum of mice were investigated through 16S rRNA high-throughput sequencing. The lowest bacterial diversity and evenness were observed in duodenal LM (DLM), followed by duodenal MAM (DMAM). Meanwhile, the bacterial diversity and evenness were obviously increased in DMAM than these in DLM, while no significant difference was observed between colonic MAM (CMAM) and colonic LM (CLM). PCoA analysis also showed that bacterial communities of LM and MAM in duodenum were completely separated, while these in colon overlapped partly. The ratio of Firmicutes to Bacteroidetes (F/B) in DMAM was significantly higher than that in DLM. Lactobacillus was largely enriched and was the characteristic bacteria in DLM. The characteristic bacteria in DMAM were Turicibacter, Parasutterella, Marvinbryantia and Bifidobacterium, while in CLM they were Ruminiclostridium₆, Ruminiclostridium₉, RuminococcaceaeUCG₀07 and LachnospiraceaeUCG₀10, and in CMAM they were LachnospiraceaeNK4A136, Mucispirillum, Alistipes, Ruminiclostridium and Odoribacter. The networks showed that more interactions existed in colonic microbiota (24 nodes and 74 edges) than in duodenal microbiota (17 nodes and 29 edges). The 16S rDNA function prediction results indicated that bigger differences of function exist between LM and MAM in duodenum than these in colon. In conclusion, microbiota from intestinal luminal content and mucosa were different both in colon and in duodenum, and bacteria in colon interacted with each other much more closely than those in duodenum.