ABSTRACT
A variety of environmental and physiological conditions are known to influence microbial composition and metabolic activities of the intestinal microflora.
Among the recognized factors within the bowel lumen are
1. Diet, substrata, and nutrient availability 2. Redox potential 3. Gas composition 4. Acidity or pH 5. Osmotic and ionic effects 6. Surface tension and liquid flow 7. Endogenous and exogenous substances that may inhibit bacterial growth (bile salts, volatile and
nonvolatile fatty acids, bacteriocides, intestinal antibodies, and drugs) 8. Bacterial interactions and competition 9. Intestinal motility
Individual microbial species vary in their sensitivity to changes in these parameters. The composition of the flora itself can affect many of these factors. Fiber has the potential to influence most of the factors listed above. This complex interactive system is only now being explored, and only partial data are available in humans.
