产细菌素苏云金芽孢杆菌的鉴定及其所产抗菌物质性质

从腌制蔬菜表面分离到一株产细菌素的菌株K2，其中和后的无细胞发酵液主要抑制革兰氏阳性细菌，特别是对芽孢杆菌有强烈的抑制作用。发酵上清液经硫酸铵盐析和透析后，仍然有很强的抗菌活性，并对多种蛋白酶敏感，表明抗菌活性物质为蛋白类物质。通过形态培养特征、生理生化特征、16S rDNA 序列比对及系统发育分析，鉴定菌株K2 是苏云金芽孢杆菌(Bacillus thuringiensis)。菌株K2 产生的抗菌物质在pH6～9 条件下80℃处理30min 仍保持稳定的抗菌活性，其对敏感菌的作用主要是杀菌，而且对芽孢萌发有很好的抑制作用。该抗菌物质在菌体生长对数中期产生，在稳定期中期抗菌活性达到最大。

Identification of Bacteriocin-producing Bacillus thuringiensis and Properties of Its Antibacterial Substances

Strain K2 having the ability to produce bacteriocin was isolated from the surface of picked vegetables. The neutralized cell-free fermentation supernatant exhibited an inhibition effect against Gram-positive bacteria, especially strong inhibition effect against Bacillus strains. The inhibition activity of the fermentation supernatant still kept high after ammonium sulphate precipitation and dialysis, and the activity of the dialysis retentate was sensitive to a variety of proteases. These results indicated the protein nature of antibacterial substances contained in the dialysis retentate. Base on morphological, physiological and biochemical characteristics, 16S rDNA sequence and phylogenic analysis, the strain K2 was classified as Bacillus thuringiensis. The antibacterial substance from strain K2 remained strong antibacterial activity after heating treatment at 80 ℃ and pH 6－9 for 30 min, suggesting its excellent thermostable property and pH resistance. The antibacterial activity was generated from midlogarithmic growth phase and reached the maximum activity at mid-stationary phase.