The effect of fermentable sugars on adhesion expression, antimicrobial activity and toxins production in gut residing acid positive bacteria.

The human microbiota includes beneficial and photogenic microorganisms that share and compete for the same niche. Probiotic bacteria are defined as bacteria whose application provides benefits for human health. Commensal probiotic bacteria transduce their health benefits to the host using three modes of action: competition with other bacteria, enhancement of the epithelial barrier and modulation of the immune response. Lactobacillus rhamnosus GG (LGG) is a Gram-positive probiotic bacterium that is naturally found in the human intestinal tract. To date, little is known about the molecular mechanisms behind the beneficial functions of LGG.

Previous work from our lab indicated that glucose can induce alternations in the LGG colony morphology and increase an antagonistic effect of LGG against several pathogenic bacteria. Moreover, condition medium produced by LGG grown with glucose inhibited the growth of pathogenic bacteria. This effect was observed over a range of pH, suggesting an action of a secreted molecule, rather than the change in the pH caused by LGG. This ability to antagonize pathogens upon exposure to glucose occurs in additional strains of Lactobacilli, and might be a general mechanism. We now systematically examine the effects of fermentable sugars compared with non-fermentable simple sugars on adhesion expression, antimicrobial activity and toxins production in gut residing acid positive bacteria.