Antibacterial activity and mechanism of phillyrin against selected four foodborne pathogens

Abstract

The antibacterial activity of phillyrin on Escherichia coli ATCC8739 (E. coli ATCC8739), Bacillus subtilis BS08, Staphylococcus aureus ATCC6538 (S. aureus ATCC6538) and Salmonella ATCC14028 was determined by filter paper method. The minimum inhibitory concentration (MIC) of the four tested bacteria was investigated by plate coating method to evaluate antibacterial ability. The antibacterial mechanism was further investigated by measuring growth curve, electric conductivity, nucleic acid content, Na⁺/K⁺-ATPase activity and polyacrylamide gel electrophoresis (SDS-PAGE). The results indicated that phillyrin had antibacterial effects and the MICs against Escherichia coli ATCC8739, Bacillus subtilis BS08, Staphylococcus aureus ATCC6538 and Salmonella ATCC14028 were 2.15, 3.16, 3.02 and 3.40 μg/mL respectively, and the antibacterial effect on Escherichia coli ATCC 8739 was more significant (p< 0.05) than that on other bacteria. Scanning electron microscopy (SEM) indicated that phillyrin destroyed the morphology of the cells and the cells ruptured. The leakage of intracellular substances led to an increase in nucleic acid content and an increase in electric conductivity in the bacterial suspension; SDS-PAGE analysis indicated that phillyrin could inhibit protein synthesis; in addition, phillyrin could reduce Na⁺/K⁺-ATPase activity. Therefore, phillyrin had obvious antibacterial ability and inhibited the expression of bacterial proteins by destroying the cell membrane structure, resulting in the death of the cells.

Keywords:
phillyrin; antibacterial mechanism; antibacterial activity