The S-layer proteins of Lactobacillus crispatus strain ZJ001 is responsible for competitive exclusion against Escherichia coli O157:H7 and Salmonella typhimurium

Abstract

Lactobacillus crispatus ZJ001, isolated from pig intestines and identified by sequencing analysis based on partial 16S rRNA gene, was examined in vitro for probiotic activity exerted by the surface layer proteins (S-layer). The characteristics of L. crispatus ZJ001 were compared to Lactobacillus acidophilus ATCC 4356 from the same genus which also produces the S-layer proteins. The strain ZJ001 was resistant to acidic condition and bile salt. Its antagonistic properties such as adhesion, inhibition of the pathogen growth and competitive exclusion against Escherichia coli O157:H7 and Salmonella typhimurium were apparently advantageous over L. acidophilus ATCC 4356. SDS-PAGE analysis of cell surface proteins revealed the presence of S-layer proteins, approximately at 42 kDa in L. crispatus ZJ001. Removal of the S-layer proteins reduced autoaggregation and adhesion to HeLa cells. The functional role of the S-layer proteins in adhesion was also confirmed by the antibody-mediated inhibition assay using the polyclonal antibody against the S-layer protein. The S-layer proteins from L. crispatus ZJ001 inhibited adhesion of S. typhimurium and E. coli O157:H7 to HeLa cells. These results suggest that L. crispatus ZJ001 possesses probiotic properties and the S-layer proteins are involved in the adhesion and competitive exclusion of pathogens to HeLa cells.