Ultrastructural Observation on Sterilization of Melittin

The effects of melittin on growth and bacteriostasis of four pathogens were extensively investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results indicated that the melittin had a marked bacteriostatic effect on the four pathogenic bacteria. Among these, E. cacotowora was influenced most powerfully and quickly, the yeast and F. fulva were the second, and the S. aureus was inhibited by a low concentration but was killed by a high concentration. It was observed in the experiments that melittin killed pathogenic bacteria in three ways. One was by pore formation. After integrating melittin into the plasma membrane, a vacuole was formed then penetrated, resulting in bacterial content leakage. The vacuole also experienced plasmolysis and the growing cavity destroyed the membrane. A third effect was the formation of vacuoles in the cells which induced the pycnosis of the cytoplasm resulting in a cell death. The mechanism of melittin bacteriostasis was the result of integrating melittin with phospholipod double layers of the plasmalemma and the endomembranes.