绞股蓝内生真菌抗大肠杆菌抗菌机制的研究

Antibacterial mechanisms of endophytic fungi from Gynostemma pentaphyllum on Escherichia coli

【目的】药用植物内生真菌是一种新型抗生素的微生物资源,研究绞股蓝内生真菌JY25的抗菌机制对内生真菌的研发具有重要意义。【方法】以二倍稀释法测定发酵液的最小抑菌浓度(MIC)和最小杀菌浓度(MBC);以MIC测定发酵液对大肠杆菌生长的抑制作用;扫描电镜观察发酵液作用下的大肠杆菌形态变化;同时,以β-半乳糖酶、碱性磷酸酶和电导率测定发酵液对细胞膜和细胞壁的损伤效果;采用考马斯亮蓝法检测发酵液对蛋白质合成的影响。【结果】JY25发酵液对大肠杆菌MIC为7 g/L、MBC为14 g/L;MIC浓度的发酵液使细菌对数生长期延迟12 h,菌体形态发生严重的畸形和破损;随着抑菌作用时间的延长,β-半乳糖酶含量增加、电导率增加,同时,实验发现大肠杆菌蛋白质合成异常,未检测到碱性磷酸酶。【结论】绞股蓝内生真菌JY25主要以破坏细菌的细胞膜及影响细菌蛋白质合成而抑制细菌生长。

[Objective] Endophytic fungi of medicine plants are the new microbial resource of antibiotic medicines. These antibacterial mechanisms of endophytic fungi named JY25 from Gynostemma pentaphyllum have important significance for the research and development of endophytic fungi. [Methods] The method of double dilution has adopted to measure the minimum inhibitory concentration （MIC） and minimum bactericidal concentration （MBC） of fermentation broth to Escherichia coli. Then, the JY25 fermentation broth with MIC concentrations was used to inhibit the growth of E. coli, and the morphology changes of E. coli were observed by scanning electron microscope. Meanwhile, β-galactosidase, alkaline phosphatase and conductivity were used to test the damaged effects of fermentation broth on E. coli cell membrane and cell wall. Finally, the effects of protein synthesis of E. coli were detected by coomassie blue method. [Results] The results showed that MIC of JY25 fermentation broth to E. coli was 7 g/L, MBC was 14 g/L, and the fermentation broth with MIC concentration could delay the logarithmic growth ofE. coli up to 12 h, with severe deformity and damage of cell morphology. With the extension of treating time, both the [3-galactosidase activity and conductivity increased, and the protein synthesis was abnormal. The alkaline phosphatase did not be detected in the broth. [Conclusion[ JY25 endophytic fungi from Gynostemma pentaphyllum primarily inhibited the growth ofE. coli by damaging the cell membranes and impacting protein synthesis.