Antibacterial mechanism of plasma sprayed Ca2ZnSi2O7 coating against Escherichia coli

In our previous work, antibacterial activity of plasma sprayed Ca2ZnSi2O7 coating has been demonstrated. However, antibacterial mechanism of Ca2ZnSi2O7 coating still remains undefined. In this study, Escherichia coli (E. coli), a kind of Gram-negative bacteria, was chosen to investigate the interactions between the bacterium and Ca2ZnSi2O7 coating. Scanning electron microscopy and transmission electron microscopy micrographs exhibited that the morphologies of E. coli on the coating changed with treatment time, from initial slight disturbance to the disruption of cell wall and drastic distortion of bacterial interior where a remarkable material-light region was formed in the center and condensed deoxyribonucleic acid (DNA) molecules were found. Disturbances of cytoplasmic membrane were observed by two-photon confocal microscopy and confirmed by leakage of intracellular potassium ion (K+). Results suggest that the destruction of cell wall and the loss of replication ability of DNA molecules are two major reasons causing death of E. coli.