In the TEM photographs shown in Fig. 2, untreated cells of E. coli
remained intact and had clearly discernible cell wall and cell membrane
with uniformly distributed cytochylema and electron-dense
materials inside. However, the cells of E. coli treated with stems
essential oil were obviously damaged. The cell wall and cytoplasmic
membrane were broken, and the electron-dense materials inside
the cell became uneven. Besides, parts of cell wall became considerably
thick and were even unable to distinguish, which indicated the
membrane lysis has occurred. The severe morphological changes of
treated cells shown on TEM images were consistent with the results
of SEM, indicating the disintegration of the cell membrane.