壳聚糖对细菌细胞膜的影响

研究了壳聚糖对大肠杆菌和金黄色葡萄球菌的抑菌性能。运用透射电子显微镜观察了壳聚糖作用前后大肠杆菌和金黄色葡萄球菌超微结构的变化；通过测定壳聚糖作用后菌液中OD260nm的变化，研究了壳聚糖对细菌细胞膜完整性的影响；通过测定壳聚糖作用后，菌悬液的上清液中所含壳聚糖残余量、乳酸脱氢酶和谷氨酰转移酶的内酶活性，考察了壳聚糖对细菌细胞外膜和内膜渗透性的影响。采用红外吸收光谱，对壳聚糖和模拟细胞膜卵磷脂间的反应产物进行表征。结果表明，壳聚糖可改变细胞内、外膜的渗透性而使细胞膜破坏，并伴随大量内溶物(DNA和mRNA)的溢出。壳聚糖与细胞膜间的作用主要是壳聚糖中的－NH3和卵磷脂中－C＝O、－P＝O形成了新的化合物引起的。

Effects of Chitosan on Bacterial Membranes

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.