engleski

Functional role of S-layer proteins in probiotic strain

S-layer proteins form a crystalline layer around the cells of several Lactobacillus species, and it has been proposed that these proteins are involved in cell protection, adherence, and surface recognition, which are important characteristics for probiotic strains. The surface proteins of probiotic strain L. acidophilus M92 were examined for the presence of S-layer, and as a standard strain was used L. acidophilus ATCC 4356 which possessed S-protein of 43 kD. Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) of cell surface proteins revealed the presence of potential surface layer (S-layer) proteins, approximated at 45 kDa in L. acidophilus M92. Southern blot with pBK1 plasmid containing slpA gene gave a positive signal, suggesting that L. acidophilus M92 has an slpA gene coding for the S-layer proteins. S-layer proteins of this strain are present during all phases of growth. The S-layer reappeared when treated cells were allowed to grow again. Removal of the S-layer proteins reduced adhesion of L. acidophilus M92 to mouse ileal epithelial cells. Furthermore, the viability of cells without S-layer was reduced in simulated gastric juice at low pH range (2, 2&middot ; ; 5, 3) and simulated pancreatic juice with bile salts (1&middot ; ; 5 g l-1 and 3 g l-1). S-layer proteins of L. acidophilus M92 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 of Lactobacillus acidophilus M92 to mouse ileal epithelial cells and has a protective role for this strain.

S-layer; probiotics; Lactobacillus acidophilus

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