The aim of this study was to investigate the effect of Bacillus subtilis against pathogens (Salmonella typhimurium and enterotoxic Escherichia coli) on the actin filament of Caco-2 cell. Bacillus subtilis and the pathogens were added to Caco-2 cell, the actin filaments in the cells was dyed by FTTC-phalloidin and the changes of actin filaments was examined by inverted fluorescence microscope. The regulatory protein Racl of actin filaments was measured by Western Blotting. The results showed that the actin filaments of Caco-2 cells in normal scattered as bundles in parallel; but the actin filaments aggregated in a small area when Salmonella typhimurium was added; the actin filaments rearranged and assemlbed with radial or disorder distribution in the center of cell when enterotoxic Escherichia coli was added; Little change occurred in actin filaments when Bacillus subtilis was added. The actin filaments of most cells scattered as bundles in parallel arrangement, and rearranged only in small amount of cells when two kinds of the pathogens and Bacillus subtilis were added together. The expression of regulatory protein Racl was significantly increased when enterotoxic Escherichia coli or Salmonella typhimurium were added to Caco-2 cells, little change occurred in the expression of Racl when two kinds of the pathogens and Bacillus subtilis were added together to Caco-2 cells. Our results revealed that enterotoxic Escherichia coli, Salmonella typhimurium could disturb the expression and distribution of actin filaments in host cells; while Bacillus subtilis could against the destruction induced by pathogenic bacteria.%本研究旨在探讨枯草芽孢杆菌拮抗2种病原菌(鼠伤寒沙门氏菌和产肠毒素大肠杆菌)对人结肠癌细胞Caco-2细胞中微丝的影响.将枯草芽孢杆菌及上述2种病原菌加到Caco-2细胞上,用异硫氰酸荧光素-鬼笔环肽标记细胞微丝,在倒置荧光显微镜下观察细胞微丝的变化；利用Western blotting检测细胞微丝调节蛋白Racl蛋白的表达变化.结果显示正常Caco-2细胞内微丝呈散在的平行排列；加鼠伤寒沙门氏菌后微丝呈小区域聚集；加产肠毒素大肠杆菌后细胞微丝重排聚集在细胞中央放射状分布或分布紊乱；单独加枯草芽孢杆菌后细胞微丝排列方式变化不大；同时分别加2种病原菌和枯草芽孢杆菌后,大部分的细胞内微丝排列整齐,只是在少部分细胞内存在微丝的聚集.产肠毒素大肠杆菌、鼠伤寒沙门氏菌可使细胞微丝调节蛋白Racl的表达显著上调,而枯草芽孢杆菌则可抑制病原菌对Racl的影响.本试验证明产肠毒素大肠杆菌、鼠伤寒沙门氏菌可影响细胞微丝的表达和分布；而枯草芽孢杆菌及其培养上清液可抑制病原菌的这种破坏作用.
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