Abstract: This work aims to detect the antibacterial action of S-layer proteins of Lactobacillus acidophilus and the combination of the S-layer proteins with antibiotics on Escherichia coli or Staphylococcus aureus. L. acidophilus was cultivated via liquid fermentation,S-layer proteins crude extract were obtained with LiCl extraction,and the S-layer proteins was purified with gel filtration chromatography. At 2 h after infecting the Caco-2 with E. coli and S. aureus respectively,the inhibition effects of S-layer proteins on E. coli and S. aureus under different concentration and different impact times were investigated,also the inhibition effect of S-layer protein combined with antibiotics on E. coli and S. aureus was studied. The experiments were grouped as：（1）control,（2）L. acidophilus,（3）S-layer proteins,（4）antibiotics,（5）L. acidophilus+ antibiotics,and （6）S-layer proteins+ antibiotics. Results showed that L. acidophilus was harvested by liquid fermentation,S-layer proteins were extracted and purified. S-layer proteins demonstrated the fine inhibition to E. coli and S. aureus in a dosage-dependent way,the inhibition rate reached 42.2% and 31.7% respectively under high concentration,and the difference was extremely significant（P<0.01）. The interference effect was obvious in short time after E. coli and S. aureus intervened,and the inhibition rate reached 59.3% and 48.4% respectively at 0 h. The inhibition rate of S-layer proteins combined with antibiotics reached 81.7% and 78.3% respectively,the difference was extremely significant（P<0.01）,and the effect was better than antibiotics alone. In conclusion,L. acidophilus S-layer proteins present strongly antibacterial effect,it can be co-used with antibiotics,and it is expected to be develop as a new type of antibacterial drug.

Key words: Lactobacillus acidophilus, S-layer proteins, pathogenic bacteria, bacteriostasis in vitro