In vitro characterization of the adhesive factors of selected probiotics to Caco-2 epithelium cell line

The aim of the present study was to analyse the type of adhesive factors of selected probiotic strains. A large number of lactic acid bacteria with intestinal and dairy origin were collected and assessed for adhesion on Caco-2 cell line. From the best adherent bacteria, four strains were selected for further research: Lactobacillus gasseri G7, L. plantarum F1, L. helveticus AC and L. delbrueckii subsp. bulgaricus B14. The average number of adhered bacteria was 17 per one Caco-2 cell in the case of L. gasseri G7 and 21 per cell in the case of L. plantarum F1. Treatment with ethylenediaminetetraacetic acid (EDTA), trypsin and metaperiodic acid in separate assays revealed that cell-bonded extracellular proteins were responsible for the adhesion of the selected L. gasseri, L. plantarum and L. helveticus strains, in contrast to the L. delbrueckii subsp. bulgaricus strain, whose adhesive factors were identified as cell-bonded exopolysaccharides. The cell-wall proteins from the first three strains were isolated, fractionated and assessed for adhesion to Caco-2 cells. Based on the attachment properties of the purified proteins towards Caco-2 cells, it was clearly proved exactly which proteins are involved in the adherence. L. plantarum F1 strain contains two adhesive proteins in contrast to the other selected strains containing one adhesive protein each. The determination of the factors mediating the adhesive abilities of the selected strains provides important information about the possible ways to preserve and increase adhesive properties towards epithelium cells.