mlnB 基因敲除对解淀粉芽孢杆菌W1杀螨活性的影响.

[Objective] This study intended to explore and verify the acaricidal mechanism of the strain Wl at the molecular level by constructing the mutant of strain Wl and detecting its acaricidal and antibacterial activities, so as to provide a new microbial resource and control strategy for the prevention and control of two-spotted spider mites, which would lay a foundation for the subsequent development and utilization of more microbial resources, and also provide a theoretical basis for the development and application of new microbial acaricides. [Method] The active compounds of secondary metabolites of B. amyloliquejaciens Wl were studied in the early stage, and it was confirmed that the acaricidal active substances were diketopiperazines, macrolides, bacimethrins and other compounds. Macrolactin A was the main acaricidal active substance in macrolide compounds, and synthesized by the mln gene cluster. By constructing knockout integration vector pBS-mlnBkanR and transforming it into natural competent cells of the Wl strain, the macrolactin A biosynthesis-defective mutant Wl timlnB : : kanR was obtained. The successful construction of the knockout mutant was confirmed by PCR amplification, product sequencing and HPLC-MS/ MS technology, and its acaricidal and bacteriostatic activities were detected. [ Result] The knockout of the mlnB gene not only resulted in the inability of stain Wl to biosynthesize macrolactin A, but also weakened its antagonistic activity against pathogens causing soft rot of cabbage, citrus canker, black rot of cabbage, and bacterial wilt of Solanaceae. Compared with 73 . 33 % - 77. 22 % of the leathality of the Wl wildtype strain, the acaricidal activity of the macrolactin A biosynthesis defective mutant was decreased by 46. 66% - SO. 55% . [Conclusion] Macrolactin A synthesized by B. amyloliquefaciens Wl strain had the activity of killing two-spotted mites, and can inhibit the activity of pathogenic bacteria of Erwinia carotovora subsp. carotovora,Xanthomonas citri subsp. citri, Xanthomonas campestris pv. campestri and Ralstonia solanacearum. After the synthesis of macrolactin A was blocked, the activity of Wl strain was obviously weakened. [ABSTRACT FROM AUTHOR]