Bacterial binding in the small intestine is mainly through the strictly carbohydrate-specific fimbrial and surface adhesins of microorganisms. As food lectins also bind in a similar sugar specific manner, there is potential competition between food lectins and bacterial adhesins of similar sugar specificities for binding to the appropriate carbohydrate containing receptors of the brush border membrane of the small intestine. Accordingly, the bacterial ecology and gut function can be modified and improved by the inclusion in the diet of natural additives, such as lectins or appropriate glycans. Therefore, the overall aim and main general objective of the project is to find specific plant lectins and/or glycoconjugates which, as natural dietary supplements, will abolish or minimize the harmful bacterial colonization of the small intestine and other parts of the gastrointestinal tract. Within this overall aim there will be a special emphasis on not only attempting to find advantageous lectins which could be us d as dietary supplements, but also to transfer the genes of such lectins into food crop plants which are part of our natural diet.
Research was carried out to find specific plant lectins and/or glycoconjugates which, as natural dietary supplements, will abolish or minimize the harmful bacterial colonization of the small intestine and other parts of the gastrointestinal tract.
The effects of a number of plant lectins, including those from the seeds of kidney and soya bean and bacterial adhesions of Escherichia coli, were to be studied in vitro on various human cells lines in culture and the effects of a number of plant lectins tested on the morphology and function of the bacterial binding to the rat small intestine in vivo.
25 lectins have been isolated and the adhesive properties of selected resident and/or pathogenic bacteria from the small intestine have been studied.
The effects of isolated lectin, bacteria, bacterial adhesions and glycoconjugates on human intestinal cells (Caco-2) were explored in respect of binding, endocytosis and functional changes in vitro. It was shown that the avidity of the in vitro binding of lectin to cells can be correlated with their known in vivo toxicity.
The influence of lectin on the gut flora and bacterial binding to the gut wall and their effects on the morphology and function of various organs, including the small intestine, kidneys, liver, pancreas and the immune system were examined in vivo in mammals, especially in rats (and pigs), after short or long term feeding with lectin rich diets.
Also, food lectin and saccharides have been tested as blockers of the binding and proliferation of harmful and/or pathogenic bacteria in the small intestine.
Finally, research into the insecticidal properties of lectin with the aim of conferring increased insect resistance has resulted in:
the identification of GNA as a natural insecticide.