| description |
It is now recognized that human intestinal microbiota plays an important role in human health. Dietary fibers are metabolized by human intestinal microbiota through hydrolysis and fermentation. However, the impact of dietary fibers on human health and on colonic microbial ecosystem remains not precisely characterized. The goal of this work was to assess the impact of natural dietary fibers on gut microbiota using an integrated approach. Through a 6 weeks nutritional intervention, 20 healthy adults alternated their own diet with controlled meals periods with 10 or 40g fibers/day. From fecal samples collected at 6 time points, we analyzed the structural and functional dynamics of microbiota by qPCR, and 454 pyrosequencing targeting the 16S rRNA genes and of metatranscriptomes. In addition, SCFA, Comet assays were measured in fecal samples and fecal waters, and statistics analysis were performed using R software. The phylogenetic approach targeting 16S rRNA genes demonstrated that the main components of the microbiota, such as Clostridium coccoides group, were significantly structured by the diet. The abundance of prevalent species, Alistipes putridinis, Dorea longicatena and Eubacterium rectale also correlated with the different diet periods. SCFA profiles were very specific of a given individual and significantly correlated with the microbiota composition. Our data indicated that a 15 days wash out is not sufficient for the microbiota structure to return to a steady state. Metatranscriptomics approach showed, as expected, that glycan degradation and methanogenesis genes were over expressed at 40g fiber/day. In a more striking way, 18 contigs, among the 1872 unassigned and not close to metagenomic datasets (EU_MetaHIT), were overexpressed, indicating new pathways deserving further characterization. This study demonstrates that increasing fibers in diet rapidly modulates intestinal microbiota dynamics and provides new insights into fiber catabolism in human digestive tract. Furthermore, we present new aspects on the degradation of fibers and we show that the genetic variability maybe explained by the individual variation or by the diet. |