Fermentable Fiber and the Gastrointestinal Tract Bacteria: Comparisons of Fiber Types and Mouse Strains

The gastrointestinal tract can be considered as a small, but complex ecosystem that is responsive to inputs (e.g., diet composition, antibiotics). The present study examined the responses of the bacteria resident in different regions of the gastrointestinal tract of two strains of mice (BALB:C and C57 Black) to three types of nondigestible oligosaccharides (NDO). Replacing the poorly fermented and insoluble ber cellulose, which was present in the diet at 10%, with three soluble NDO (oligofructose, inulin, lactosucrose) increased the densities of anaerobes, aerobes, as well as lactobacilli and streptococci, and decreased enterics and E. coli. The magnitude of responses was not consistent for the two strains of mice, regions of the gastrointestinal tract, and for the three NDO. Furthermore, differences were detected for the responses of two shipments of the C57 Black mice. Our ndings indicate that 1) NDO can be used to manage the composition of the gastrointestinal tract bacteria, 2) there is a need to identify specic NDO or combinations that will elicit the greatest health benets as well as the species of bacteria that are responsive, and 3) because of variability among gastrointestinal ecosystems caution is needed when extrapolating results obtained from one species, strain, individual, or one region of the gastrointestinal tract. Ke