Adhesion of microbes to the intestinal surface: lessons from the paradigm probiotic Lactobacillus rhamnosus GG

The human gastrointestinal tract (GI-tract) is heavily colonized by a multitude of microbes, collectively called the microbiota. The microbiota provide us with metabolic capabilities not encoded in the human genome, e.g. the ability to utilize energy stored in dietary polysaccharides otherwise indigestible to us. Our microbiota also protects us against pathogens by competing for nutrients and binding sites within the GI-tract. Furthermore, given that cells of the GI-tract microbiota outnumber those of the host by ten-fold, this microbial ecosystem can be viewed as ‘an organ in an organ’. The GI-tract microbiota has been a subject of intensive research during the last years, and its importance in health and disease is only starting to be realized because of recent breakthrough observations linking the human microbiota composition with major human diseases, such as diabetes and obesity. As the knowledge about the GI-tract microbiota composition and its impact on host health begins to accumulate, undoubtedly much of the research focus will shift from the systems level toward individual species and molecules. Consequently, there will be an increasing need for reductionist/functional proteomic approaches to identify and characterize the various ‘molecular players’ being utilized by different bacteria during their attachment to the intestinal epithelium of both healthy and diseased hosts. In this review we will highlight our recent findings about mucus adhesion mechanisms of the paradigm probiotic Lactobacillus rhamnosus GG.