Abstract:

The antibacterial activities of chitosan against Escherichia coli(E. coli)and Staphylococcus aureus (S .aureus)were studied in vitro. To investigate the action mode of chitosan, morphologies of chitosan-treated E. coli and S. aureus were observed by transmission electron microscopy（TEM）, the integrity of cell membranes of tested bacteria was determined by measuring the released materials at 260 nm, and the permeabilities of the outer membrane (OM) and inner membrane (IM) were analyzed by measuring the residue amount of chitosan and the release of cytoplasmic lactic dehydrogenase and glutamyl transpeptidase activity. In addition, the reaction product of chitosan and phosphatidylcholine (PC) was characterized by Fourier-transform infrared spectroscopy (FT-IR). The results indicated that chitosan may disrupt bacterial membranes with release of cellular contents by changing the permeabilities of cell OM and IM. This damage is likely caused by the electrostatic interaction between －NH3 groups of chitosan and －C = O or －P = O of phospholipid components in cell membrane.

Key words: chitosan, antibacterial activity, cell membrane, effect