【摘要】 枯草芽孢杆菌G3菌株正在登记为防治番茄叶霉病的生物杀菌剂。为改进该菌的抗真菌活性,用诱变剂吖啶橙诱变得到20个突变株,其中5个突变株Ga1、Ga8、Ga12、Ga1和Ga19在肉汤和PDA平板上形成粘液状菌落,完全不同于出发菌株。PDA平板抑菌圈试验,突变株对番茄叶霉菌和黄瓜灰霉菌产生比野生株G3更大的透明抑菌圈。其中Ga1菌株对番茄叶霉菌和黄瓜灰霉菌的抑菌带宽分别是G3的1.71和1.69倍。用番茄叶霉菌为指示菌的生物测定结果表明,突变株固体培养物或摇瓶培养物以最小抑菌浓度(M IC)和有效抑菌中浓度(EC50)表示的抗真菌活性皆高于G3菌株。抗真菌活性以Ga1>Ga8>Ga19>Ga12>Ga13>G3为序。参试菌株培养物的抗真菌活性与菌量(CFU)不相关,而与甲醇抽提代谢物的干重,尤其是伊枯草菌素A含量呈一定的正相关。突变株Ga1抗真菌活性最强,固体培养物或摇瓶培养物均是G3的3倍左右。摇瓶培养时,伊枯草菌素A动态分泌曲线表明,Ga1菌株产生比G3更多的伊枯草菌素A。Ga1菌株增强了合成伊枯草菌素A的能力。更多还原

【Abstract】 Bacillus subtilis strain G3 is an active component of the biofungicide being registered to control tomato leaf mold disease caused by Cladosporium fulvum.For improvement of antifungal activity of the bacterium,acridine orange was used to produce mutants.Among the 20 mutants obtained,Ga1,Ga8,Ga12,Ga13 and Ga19 produced the mucous-type colonies on nutrient broth and PDA agar plates which were different from the colony of original strain.Inhibition tests against Cladosporium fulvum and Botrytis cinerea on PDA plates indicated that the mutants produced bigger and clear inhibition zones than the wild type G3.The Inhibition zone of Ga1 was 1.71 and 1.69 times wider than that of G3 to C.fulvum and B.cinerea respectively.MIC and EC50 of the five mutants against C.fulvum were lower than that of G3 whether cultured in solid substrate or liquid.The order of the antifungal activity was Ga1>Ga8>Ga19>Ga12>Ga13>G3.There was no correlation between the antifungal activity and cfu of the mutants,but a positive correlation between the antifungal activity and the amount of metabolites extracted with methanol,specially the amount of iturin A was observed.Mutant Ga1 showed the highest antifungal activity as about 3 times than original strain G3.Time course of iturin A production in shake flask cultures showed that Ga1 was an improved mutant with enhanced capacity to synthesize iturin A.更多还原