Adhesion mechanisms of lactic acid bacteria: conventional and novel approaches for testing.

Adhesion ability is a primary criterion for the selection of probiotic microorganisms. Lactic acid bacteria contribute the majority of microorganisms with probiotic properties. They have several important mechanisms for intestinal epithelial cell adhesion. In order to adhere to the intestinal cells, they generally use various structures such as flagella, pili, S layer proteins, lipoteichoic acid, exopolysaccharides and mucus binding proteins. Various in vitro experiments were designed or study models were developed to reveal the mechanisms they utilize for binding to the intestinal cells, yet, the mechanisms for their adhesion are not fully explained. The major disadvantage of conventional models is the lack of layers forming the intestinal mucosa. Besides, these models omit the presence of natural microbiota, digestive conditions and the presence of a food matrix. Because of the disadvantages of existing models, natural tissues or novel applications like 3D organ cultures, which are better able to mimic in vivo conditions, are preferred.