Department of Plant Medicine, National Pintung University of Science and Technology, Pintung, 91201, Taiwan.
Department of Biotechnology, National Kaohsiung Normal University, Kaohsiung, 824444, Taiwan.
Appl Biochem Biotechnol. 2020 May;191(1):191-200. doi: 10.1007/s12010-020-03289-8. Epub 2020 Feb 26.
Photorhabdus luminescens is an entomopathogenic rod-shaped bacterium infected with insect nematodes of the Heterorhabditidae family. It kills insects through the secretion of high molecular weight toxin complexes. In this study, Plutella xylostella larvae were orally administered P. luminescens for bioassay. After incubation in Luria-Bertani (LB) medium for a sufficiently long period, the mortality rates of P. xylostella observed after diluting the fermentation broth 50 times and diluting the supernatant 5 times were 18.89% and 91.11%, respectively. Retentates measuring more than 70 kDa showed 88% mortality after ultrafiltration (UF) membrane treatment. Thus, the supernatant of P. luminescens had insecticidal activity, and the main insecticidal toxin complexes had a molecular weight exceeding 70 kDa. The L (3) Taguchi orthogonal experimental optimized medium mode-predicted insecticidal activity levels were 84% and 119% in the 50-fold diluted fermentation broth and 5-fold diluted supernatant, respectively. Moreover, the insecticidal activity was improved to 92.2% in the 100-fold diluted fermentation broth and to 97.8% in the 10-fold diluted supernatant in the experiments. All combinations tested showed clear indications of lethality, including swelling, vesicle formation, cytoplasm vacuolization, and brush border membrane lysis. Thus, these results promote the use of P. luminescens 0805-P2R as a potent biopesticide to effectively control P. xylostella.
发光杆菌是一种感染异小杆线虫科昆虫线虫的昆虫病原杆状细菌。它通过分泌高分子量毒素复合物来杀死昆虫。在本研究中，小菜蛾幼虫通过口服方式摄入发光杆菌进行生物测定。在 Luria-Bertani（LB）培养基中孵育足够长的时间后，将发酵液稀释 50 倍和稀释上清液 5 倍后观察到小菜蛾的死亡率分别为 18.89%和 91.11%。截留物大于 70 kDa 的超滤（UF）膜处理后显示出 88%的死亡率。因此，发光杆菌的上清液具有杀虫活性，主要杀虫毒素复合物的分子量超过 70 kDa。L（3）Taguchi 正交实验优化的培养基模式预测 50 倍稀释发酵液和 5 倍稀释上清液中的杀虫活性水平分别为 84%和 119%。此外，在实验中，100 倍稀释发酵液中的杀虫活性提高到 92.2%，10 倍稀释上清液中的杀虫活性提高到 97.8%。所有测试的组合都表现出明显的致死迹象，包括肿胀、泡囊形成、细胞质空泡化和刷状缘膜裂解。因此，这些结果促进了将发光杆菌 0805-P2R 用作有效的生物农药来有效控制小菜蛾。
