Southern Illinois University Edwardsville, Biological Sciences, Edwardsville, IL 62026
Many epidemiological studies have shown that fiber in the diet can lower a person’s risk of developing colon cancer. However, the mechanism for such an effect has remained obscure. There is evidence that this protective effect is mediated by soluble fiber in the diet binding to lectins. Lectins are proteins from a variety of sources, which are resistant to digestion and bind to sugar residues on cell-surface receptors. Once bound to a cell, they are mitogenic, causing the cell to begin to divide more rapidly. Binding of dietary lectins to colon epithelium cells could start them on the pathway to becoming cancerous. But, sugar residues in the polysaccharides that compose soluble fiber could bind lectins, preventing them from attaching to colon cells. We are investigating the possibility that bacteria mutants in the colon could be selected to utilize soluble fiber polysaccharides more efficiently than wild-type and thus lower their protective effect. We are developing a model system using E. coli, and are searching for mutants which can utilize galactose more efficiently than an isogenic wild-type. We report here that we have found such a mutant, CH6, which grows more rapidly than wild-type when the two strains are grown together and given only galactose as carbon source.
[Abstract (DOC)]