Abstract
Fructooligosaccharides (FOS) are considered prebiotics and have been proven to selectively promote the growth of Bifidobacterium in the gut. This study aimed to clarify the effects of FOS intake on the composition of luminal and mucosal microbiota in mice. Briefly, mice were fed a 0% or 25% FOS (w/w)-supplemented diet for four weeks, and the composition of luminal and mucosal microbiota, especially the Bifidobacterium, was analyzed by sequencing the V3–V4 region of 16S rRNA and groEL gene, respectively. After FOS intervention, there were significant increases in the total and wall weights of the cecum and the amount of total short-chain fatty acids (SCFAs) in the cecal contents of the mice. At the phylum level, the results showed a significant increase in the relative abundance of Actinobacteria in the contents and mucosa from the cecum to the distal colon in the FOS group. Besides Bifidobacterium, a significant increase was observed in the relative abundance of Coprococcus in all samples at the genus level, which may be partially related to the increase in butyric acid levels in the luminal contents. Furthermore, groEL sequencing revealed that Bifidobacterium pseudolongum was almost the sole bifidobacterial species in the luminal contents (>98%) and mucosa (>89%). These results indicated that FOS can selectively promote B. pseudolongum proliferation in the intestine, either in the lumen or the mucosa from the cecum to the distal colon. Further studies are required to reveal the competitive advantage of B. pseudolongum over other FOS-metabolizing bacteria and the response mechanisms of B. pseudolongum to FOS.
Highlights
The human gastrointestinal tract is an open microbial ecosystem with trillions of bacteria [1,2], including the beneficial and harmful bacteria that together form the normal intestinal microflora
Compared withwas the observed mice in in thethis control significant enlargement the cecum and of the luminal contents study, group, which might be explained by theof results showing softening of the luminal contents was observed in this study, which might be explained by the results that oligosaccharides supplementation increased the water content of the feces [20]
1), indicating that the cecal wall thickness did not decrease with the cecal size and this finding may be related to the production of short-chain fatty acids (SCFAs) in thethe increase the cecum cecal size and this may be related to theand production of SCFAs cecum
Summary
The human gastrointestinal tract is an open microbial ecosystem with trillions of bacteria [1,2], including the beneficial and harmful bacteria that together form the normal intestinal microflora. The cecum and colon are denser and more diverse bacterial habitats than the stomach and small intestine. Because of the differences in physiological structures and the Nutrients 2019, 11, 2431; doi:10.3390/nu11102431 www.mdpi.com/journal/nutrients. Nutrients 2019, 11, 2431 gradients in available nutrients along the small intestine and colon, the composition of the bacterial community changes longitudinally [5,6]. The luminal microbiota differ from the mucosal microbiota within the same segment [7]. Most studies on intestinal microbiota have focused on feces rather than luminal and mucosal samples because feces are readily available [8,9]. Luminal and mucosal samples of the cecum and colon should be investigated to understand the distribution, composition, and gradual changes of gut microbiota along the gastrointestinal tract
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