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蜡样芽孢杆菌(Bacillus cereus)B3-7是一株对于小麦全蚀病具有有效生防作用的小麦内生细菌。为了研究B3-7在小麦根内的定殖机制,本研究将含有转座子TnYLB-1和温度敏感型复制子的质粒pMarB转化B3-7菌株,高温处理后TnYLB-1插入细菌基因组中,构建转座子插入突变体库。通过筛选,获得1株在小麦根内定殖能力显著降低的突变体B3-7-458。利用反向PCR方法分离转座子插入位点的侧翼序列并分析其特征,发现转座子插入导致细菌鞭毛运动性相关基因mota失活,同时发现mota失活菌株对于小麦全蚀病的生防能力降低。通过构建互补载体对突变基因mota进行互补分析,发现互补菌株的运动性、在小麦根系内部的定殖能力以及对于小麦全蚀病的生防能力得以恢复。本研究证明了生防菌蜡样芽孢杆菌B3-7的mota基因参与该菌株在小麦根系的内生定殖,也参与了该菌株对于小麦全蚀病的生物防治。
Bacillus cereus B3-7 is an endophytic bacteria in wheat that has an effective biocontrol effect on wheat eclipse. In order to study the colonization mechanism of B3-7 in wheat roots, the plasmid pMarB containing transposon TnYLB-1 and temperature-sensitive replicon was transformed into B3-7 strain. TnYLB-1 was inserted into the bacterial genome after high temperature treatment, Transposon insertion mutants were constructed. By screening, a strain B3-7-458 with significantly reduced colonization ability in wheat roots was obtained. Reverse PCR was used to separate the flanking sequences of the transposon insertion site and analyze its characteristics. It was found that transposon insertion resulted in the inactivation of bacterial flagella motility-related gene mota, and at the same time, it was found that mota-inactivated strains were biocontrol agents for wheat eclipse Decreased ability. Through the complementation analysis of the mutated gene mota by constructing the complementary vector, it was found that the motility of the complementary strains, the colonization ability within the wheat root system and the biocontrol ability against the total eclipse of wheat were recovered. This study proved that the biocontrol bacterial Bacillus cereus B3-7 mota gene involved in this strain of endogenic colonization of wheat roots, but also involved in the bacterial eclipses for the biological control of wheat.