Functionality of the S-layer proteins from Lactobacillus in the competitive against enteropathogens infection

The interest of probiotics as remedy for a broad number of infectious diseases has gained wide interest over the last few years, but little is known about their underlying mechanism of action. In this study, five selected Lactobacillus isolated from human intestinal and ferment milk were preliminarily identified by 16S rDNA gene sequencing and assessed the ability to inhibit the adhesion of enteropathogens using HT-29 cells model through a process which may be related to specific components of the bacterial surface. Surface layer proteins are located in a paracrystalline layer outside the bacterial cell wall and are thought to play a role in tissue adherence. Removal of S-layer proteins from the Lactobacillus (treated with 5 M LiCl) reduced inhibition activity as revealed in exclusion, competition and displacement assays, which suggested that S-layer proteins had involved in the adhesion of probiotics. SDS-PAGE analysis confirmed the presence of S-layer proteins with dominant band which was approximately 60 kDa. Further analysis of S-layer proteins revealed that the hydrophobic amino acids accounted for 43.2 % of the total amino acid for the Lactobacillus paracasei M7. So, these probiotics could be used in the health-promoting food products, which could prevent the diarrhea caused by pathogens.