Effects of Lactobacillus acidophilus S-layer Protein on Adhesion to Intestinal Cells and Macrophage Proliferation

To investigate the autoaggregation and adherence rate to HT-29 cells of Lactobacillus acidophilus ATCC4356 with or without S-layer protein as well as the influence of S-layer protein on the proliferation and lysosomal secretion of macrophages, S-layer protein of L. acidophilus ATCC 4356 was extracted by 4 M lithium chloride, followed by further purification using centrifugation, dialysis, and microfiltration. The molecular weight was then confirmed by SDS-PAGE. Autoaggregation rate of L. acidophilus at 37 ℃was measured by using a microplate reader during the incubation(0 to 5.5 h). Adhesion of L. acidophilus ATCC4356 to HT-29 cells was observed by light microscopy. After incubation of S-layer proteins with RAW 264.7 macrophages for 2 h, proliferation and changes in lysosomal secretion were evaluated by MTS and Lyso-Tracker Red, respectively. The results showed that the protein extracted was S-layer protein from L. acidophilus ATCC 4356 with a molecular weight of about 46 ku. L. acidophilus ATCC4356 autoaggregation rate and adhesion to HT-29 cells were reduced when the S-layer protein was removed. L. acidophilus ATCC 4356 autoaggregation rate increased as the incubation time was extended. S-layer protein could also promote macrophage proliferation and lysosomal secretion.