Abstract:In this study, the antibacterial activity and underlying mechanism of the potato trypsin inhibitor (PTI) was investigated. To evaluate the antibacterial activity of PTI, the inhibition zone diameter (DIZ) was determined through the filter paper diffusion method, and the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were determined by the double microdilution method. The antibacterial mechanism of PTI was explored through observations by scanning electron microscopy, and measurements of cell membrane’s permeability and integrity, intracellular reactive oxygen content as well as inhibition rate of bacterial protease. The results showed that PTI exhibited significant inhibitory effects against Bacillus subtilis, Bacillus cereus and Pseudomonas aerimonas with the corresponding diameters of bacteriostatic zone as 12.56 mm, 12.35 mm and 11.76 mm, respectively, MIC ranging from 1.88 to 3.75 mg/mL, and MBC being the same for the three bacteria (3.75 mg/mL). PTI destroyed the morphology of bacterial cells and led to the increases of relative conductivity and leakage of nucleic acid in the bacterial suspension, which affected the membrane permeability of bacteria. Fluorescence microscopic images showed that PTI at the concentration of MIC destroyed the integrity of the bacterial cell membrane, promoted the production of intracellular ROS, causing oxidative damage to the bacterial cells. PTI showed a certain inhibitory effect on the activity of bacterial protease. Based on the experimental results, it is concluded that PTI probably exerts its antibacterial activity through such a multi-target synergistic effect.
