A fibrolytic potential in the human ileum mucosal microbiota revealed by functional metagenomic
Résumé
The digestion of dietary fibers is a major function of the human intestinal microbiota. So far this
function has been attributed to the microorganisms inhabiting the colon, and many studies have
focused on this distal part of the gastrointestinal tract using easily accessible fecal material. However,
microbial fermentations, supported by the presence of short-chain fatty acids, are suspected to occur in
the upper small intestine, particularly in the ileum. Using a fosmid library from the human ileal mucosa,
we screened 20,000 clones for their activities against carboxymethylcellulose and xylans chosen as
models of the major plant cell wall (PCW) polysaccharides from dietary fibres. Eleven positive clones
revealed a broad range of CAZyme encoding genes from Bacteroides and Clostridiales species, as well
as Polysaccharide Utilization Loci (PULs). The functional glycoside hydrolase genes were identified, and
oligosaccharide break-down products examined from different polysaccharides including mixed-linkage
β-glucans. CAZymes and PULs were also examined for their prevalence in human gut microbiome.
Several clusters of genes of low prevalence in fecal microbiome suggested they belong to unidentified
strains rather specifically established upstream the colon, in the ileum. Thus, the ileal mucosa-
associated microbiota encompasses the enzymatic potential for PCW polysaccharide degradation in the
small intestine.
Domaines
Sciences du Vivant [q-bio]| Origine | Fichiers produits par l'(les) auteur(s) |
|---|
Loading...