Study On Cell Surface Characteristics Of Probiotic Lactobacilli

The surface physicochemical properties and chemical components such as cell surface hydrophobicity and auto-aggregation, capsular polysaccharides (CPS) and cell surface proteins contribute to the interaction of lactobacilli with the host tissues. Surface properties play an important role in the probiotic effects of Lacobacillus. In this study, a CPS-producing L. plantarum C88 isolated from traditional fermented products was used to investigate the specific roles of cell surface CPS and proteins in probiotics. The results are as follows:Using L. plantarum C88 as an original strain for treatment with nitrosoguanidine, screening with negative staining and observing with optical microscope and electron microscopy, the capsule-deficient mutant strain was obtained, it was named L. plantarum C88M3. On the basis of the results of 16s rDNA sequence analysis, growth curve and RAPD analysis, compared with the wild type strain C88, the mutant strain C88M3 showed the difference in genetic characteristics and CPS production.Compared with the mutant strain C88M3, the wild type strain C88 shows higher resistance to low pH and bile salts and better adhesion ability to porcine gastric mucin and Caco-2 cells. The results demonstrated that a protective coating of CPS may enhance tolerance to harmful environment and improve cell surface physicochemical properties to increase bacterial adherance to the intestinal mucosa and raise colonization of lactobacilli.A neutral CPS produced by L. plantarum C88 was purified by exchanging chromatography on DEAE-cellulose column and gel permeation chromatography on Sepharose CL-6B and its structure was determined by HPLC and FTIR spectroscopy. Monosaccharide analysis of the purified CPS sample showed that the CPS of L. plantarum C88 was composed of mannose, glucose and galactose in a molar ratio of 1:1:1. The molecular mass of the CPS was determined to be 1.31x106Da.The cell surface proteins involved in the adhesion of L. plantarum C88 were extracted by different methods. Among the methods tested, treatment with 4 mol/L guanidine-HCl and 5mol/L LiCl appeared to be the most suitable for surface protein extraction in this strain. Surface protein extracts were subjected to proteomic analysis using SDS-PAGE electrophoresis, tryptic digestion, chip-LC-QTOF mass analysis and protein identification using database search. Two adhesion-associated proteins are identified as GroEL chaperone protein and elongation factor-Tu.