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Genomics, Proteomics, and Metabolomics

Diets Enriched in Oat Bran or Wheat Bran Temporally and Differentially Alter the Composition of the Fecal Community of Rats^1–3,

⁴ Bureau of Nutritional Sciences, Health Canada, Ottawa K1A 0K9, Ontario, Canada; ⁵ University of Ontario Institute of Technology, Oshawa L1H 7K4, Ontario, Canada; ⁶ Department of Biological Sciences, University of Lethbridge, Lethbridge T1K 3M4, Alberta, Canada; and ⁷ Atlantic Food and Horticulture Research Center, Agriculture and Agri-Food Canada, Kentville B4N 1J5, Nova Scotia, Canada

A clear understanding of how diet alters gastrointestinal communities is important given the suggested link between gut community composition and a wide variety of disease pathologies. To characterize this link for commonly consumed dietary fiber sources, we investigated the change in the fecal community of rats fed diets containing 5% nonnutritive fiber (control), 3% (wt:wt) oat bran plus 2% nonnutritive fiber (OB), or 5% (w/w) wheat bran (WB) over a 28-d feeding trial using both molecular- and cultivation-based methodologies. Pooled fecal samples from 8 rats fed the same diet were analyzed at 4 time points. On d 28, bran-fed rats had approximately twice the total cultivable bacteria than rats fed the control diet. Over the course of feeding, the cultivable community was initially dominated by bacteroides, then by bifidobacteria, lactobacilli, enterococci, and various enterics. In contrast, molecular analysis revealed the appearance of new operational taxonomic units (phylotypes) that were both temporally and inequitably distributed throughout the fecal community. The majority of change occurred in 2 major lineages within the Firmicutes: the Clostridium coccoides group and the Clostridium leptum subgroup. The time course of change depended on the source of bran, with the majority of new phylotypes appearing by d 14 (OB) or d 28 (WB), although adaptation of the fecal community was slow and continued over the entire feeding trial. Bacterial community richness was higher in bran-fed rats than in those fed the control diet. Change within the C. coccoides and C. leptum lineages likely reflect their high abundance within the gut bacterial community and the role of clostridia in fiber digestion. The results illustrate the limitations of relying solely on cultivation to assess bacterial changes and illustrate that community changes are complex in an ecosystem containing high numbers of interdependent and competing species of bacteria.

^* To whom correspondence should be addressed. E-mail: steve_brooks{at}hc-sc.gc.ca.

Manuscript received 5 May 2009. Initial review completed 21 May 2009. Revision accepted 25 August 2009.

Published online 23 September 2009.