Strain Hd-nk413 Antibacterial Substances Purified And Anti-potato Early Blight Mechanism

Potato is the fourth grain crops following with rice, wheat and maize in the world, nevertheless, the potato early blight occured frequently in recent years, it did great harm on the development of potato industry. Streptomyces albulus HD-NK413 had strong inhibitory effect on Alternaria solani. In this study, the antibiotic substance produced by HD-NK413 was primary isolated and purified, and the possible antifungal mechanism was studied.The fermentation liquid of HD-NK413 was analysed the antagonistic components on Alternaria solani in fermentation by thin layer chromatography and purified by active carbon adsorption and silica gel column chromatography. The optimum condition on the activated carbon's absorption was confirmed. The fermentation was static absorped 12h under the condition of a natural pH value, while volumic ratio of particle active charcoal to fermentation was 1:1. Absorbed antifungal substance was static eluted with 50% acetone solution at pH6, and volumic ratio of particle active charcoal to 50% acetone solution was 1:4. There were three chromatographic peaks after silica gel column chromatography, two of them are single-component groups whose Rf is 0.83,0.86 on the silica gelGF254, and they have biological bacteriostatic activity. The ultraviolet absorption peak of the two components was at 272nm and 271nm, respectively. The antifungal substance can be preliminarily ascertained to be a kind of nucleoside antibiotic according to their absorption characteristics.The result of basic research on antifungal mechanism against Alternaria solani by crude extracted from the fermentation liquid of HD-NK413 showed that, the crude not only had strong inhibitory effect on mycelia growth but also had killing effect to Alternaria solani. The mycelium tips treated by the crude appeared dilatometer bulbble and malformation growth; most of mycelium became shorter and smaller; septum structure became unclear, even nearly disappeared.20 hours after treatment by the crude, most of mycelium was ablated, the few remaining mycelium was thin and without branch, the cell wall became fuzzy, the protoplast was shrinkage. The hyphal structure had suffered serious damage.The result of hyphal physiological index of Alternaria solani treated by antibiotic crude indicated that, the antibiotic substance could increase the cell membrane permeability and lead protoplast to betray; it could inhibit the synthetic of ergo sterol in cell wall; it could make cell membrane occurred lipid peroxidation to destroy the function; it could break the dynamic balance of defense enzyme system in the cell, such as superoxide dismutase(SOD), catalase(CAT) and peroxidase(POD), and the cell was damaged by oxygen free radical, moreover, the degree of lipid peroxidation of cell membranes was deepen continuously, finally, the fungal mycelium have suffered serious damage.