Biocontrol Efficiency of Bacillus subtilis SL-13 and Characterization of an Antifungal Chitinase

The seed germination and tomato seedling tests showed that Bacillus subtilis SL-13 could promote the sprouting and seedling growth of tomato.The fresh and dry weight of tomato seedlings increased 42.86%and 18.75%,respectively.The control efficacies of the SL-13 to tomato Rhizoctonia rot were 20.65%and 35.23%in the greenhouse and field,respectively.The growth of the plant-pathogenic fungus Rhizoctonia solani was considerably inhibited in the presence of the strain SL-13 culture supernatant.The main antifungal protein was detected to be chitinase through vitro assay.The chitinase was purified with DEAE-Sepharose fast flow ion exchange column chromatography and Sephadex G-75 gel filtration for further characterization.The optimal pH and temperature for the chitinase activity were 7.0 and 50°C,respectively.It was demonstrated that the enzyme was stable at pH 5-9 and 40-60°C.70%of the enzyme activity was retained when incubated at 121°C and 0.11 MPa for 20 min,and the enzyme was not sensitive to protease K and ultraviolet radiation.Thus it is suitable for effective biological control in relatively unstable environment.

种子萌芽和西红柿幼苗测试证明杆菌 subtilis SL-13 能支持发芽和西红柿的幼苗生长。西红柿幼苗的新鲜、干燥的重量分别地增加了 42.86% 和 18.75% 。到西红柿 Rhizoctonia 的 SL-13 的控制功效腐烂分别地在温室和域是 20.65% 和 35.23% 。植物病原的真菌 Rhizoctonia solani 的生长更加面对紧张 SL-13 文化上层清液被禁止。主要抗真菌的蛋白质被检测是通过 vitro 试金的 chitinase。chitinase 为进一步的描述与 DEAE-Sepharose 快流动离子交换列层析和 Sephadex G-75 胶化过滤被净化。为 chitinase 活动的最佳的 pH 和温度是 7.0 和 50 (C 分别地。酶在 pH 5-9 和 40-60 是稳定的，这被表明(C。当在 121 点孵化了时， 70% 酶活动被保留(为 20 min 的 C 和 0.11 MPa，和酶不对朊酶 K 和紫外放射敏感。因此它对在相对不稳定的环境的有效生物控制合适。