Fucosylation of intestinal epithelial cells, catalyzed by fucosyltransferase 2 (Fut2), is a major glycosylation mechanism of host–microbiota symbiosis. Commensal bacteria induce epithelial fucosylation, and epithelial fucose is used as a dietary carbohydrate by many of these bacteria. However, the molecular and cellular mechanisms that regulate the induction of epithelial fucosylation are unknown. Here, we show that type 3 innate lymphoid cells (ILC3) induced intestinal epithelial Fut2 expression and fucosylation in mice. This induction required the cytokines interleukin-22 and lymphotoxin in a commensal bacteria–dependent and –independent manner, respectively. Disruption of intestinal fucosylation led to increased susceptibility to infection by Salmonella typhimurium. Our data reveal a role for ILC3 in shaping the gut microenvironment through the regulation of epithelial glycosylation.

A highly sensitive quantitative PCR detection method has been developed and applied to the distribution analysis of human intestinal bifidobacteria by combining real-time PCR with Bifidobacterium genus-and species-specific primers. Real-time PCR detection of serially diluted DNA extracted from cultured bifidobacteria was linear for cell counts ranging from 10 6 to 10 cells per PCR assay. It was also found that the method was applicable to the detection of Bifidobacterium in feces when it was present at concentrations of >10 6 cells per g of feces. Concerning the distribution of Bifidobacterium species in intestinal flora, the Bifidobacterium adolescentis group, the Bifidobacterium catenulatum group, and Bifidobacterium longum were found to be the three predominant species by examination of DNA extracted from the feces of 46 healthy adults. We also examined changes in the population and composition of Bifidobacterium species in human intestinal flora of six healthy adults over an 8-month period. The results showed that the composition of bifidobacterial flora was basically stable throughout the test period.

16S rRNA gene-targeted group-specific primers were designed and validated for specific detection and quantification of the Clostridium leptum subgroup and the Atopobium cluster. To monitor the predominant bacteria in human feces by real-time PCR, we used these specific primers together with four sets of groupspecific primers for the Clostridium coccoides group, the Bacteroides fragilis group, Bifidobacterium, and Prevotella developed in a previous study (

Recent studies have demonstrated that gut microbiota development influences infants' health and subsequent host physiology. However, the factors shaping the development of the microbiota remain poorly understood, and the mechanisms through which these factors affect gut metabolite profiles have not been extensively investigated. Here we analyse gut microbiota development of 27 infants during the first month of life. We find three distinct clusters that transition towards Bifidobacteriaceae-dominant microbiota. We observe considerable differences in human milk oligosaccharide utilization among infant bifidobacteria. Colonization of fucosyllactose (FL)-utilizing bifidobacteria is associated with altered metabolite profiles and microbiota compositions, which have been previously shown to affect infant health. Genome analysis of infants' bifidobacteria reveals an ABC transporter as a key genetic factor for FL utilization. Thus, the ability of bifidobacteria to utilize FL and the presence of FL in breast milk may affect the development of the gut microbiota in infants, and might ultimately have therapeutic implications.

For the detection and identification of predominant bacteria in human feces, 16S rRNA-gene-targeted groupspecific primers for the Bacteroides fragilis group, Bifidobacterium, the Clostridium coccoides group, and Prevotella were designed and evaluated. The specificity of these primers was confirmed by using DNA extracted from 90 species that are commonly found in the human intestinal microflora. The group-specific primers were then used for identification of 300 isolates from feces of six healthy volunteers. The isolates were clearly identified as 117 isolates of the B. fragilis group, 22 isolates of Bifidobacterium, 65 isolates of the C. coccoides group, and 17 isolates of Prevotella, indicating that 74% of the isolates were identified with the four pairs of primers. The remaining 79 isolates were identified by 16S ribosomal DNA sequence analysis and consisted of 40 isolates of Collinsella, 24 isolates of the Clostridium leptum subgroup, and 15 isolates of disparate clusters. In addition, qualitative detection of these bacterial groups was accomplished without cultivation by using DNA extracted from the fecal samples. The goal for this specific PCR technique is to develop a procedure for quantitative detection of these bacterial groups, and a real-time quantitative PCR for detection of Bifidobacterium is now being investigated