Importance of S-layer proteins in probiotic activity ofLactobacillus acidophilusM92.

j. frece, b. kos, i.k. svetec, z. zgaga, v. mrša and j.šušković. 2004.To investigate the functional role of surface layer proteins (S-layer) in probiotic strainLactobacillus acidophilusM92, especially its influence on adhesiveness to mouse ileal epithelial cells.Sodium dodecyl sulphate polyacrylamide gel electrophoresis of cell surface proteins revealed the presence of potential surface layer (S-layer) proteins,caat 45 kDa inL. acidophilusM92. Southern blot with pBK1 plasmid, containingslpAgene, gave a positive signal, suggesting thatL. acidophilusM92 has aslpAgene coding for the S-layer proteins. S-layer proteins of this strain are present during all phases of growth. The S-layer proteins appeared when cells treated with 5 mol l−1 LiCl were allowed to grow again. Removal of the S-layer proteins reduced adhesion ofL. acidophilusM92 to mouse ileal epithelial cells. Furthermore, the viability of cells without S-layer were reduced in simulated gastric juice at low pH range (2, 2·5, 3) and simulated pancreatic juice with bile salts (1·5 and 3 g l−1). S-layer proteins ofL. acidophilusM92 were resistant to pepsin and pancreatin, in contrast, the treatment with proteinase K led to a significant proteolysis of the S-layer proteins.These results demonstrated functional role of S-layer; it is responsible for adhesiveness ofLactobacillus acidophilusM92 to mouse ileal epithelial cells and has a protective role for this strain.S-layer proteins have an important role in the establishment of probiotic strainLactobacillus acidophilusM92 in the gastrointestinal tract. [ABSTRACT FROM AUTHOR]