球形芽孢杆菌Mtx1蛋白和苏云金杆菌Cyt1Aa晶体蛋白的协同作用

The synergism between Mtx1 from Bacillus sphaericus and Cyt1Aa from Bacillus thuringiensis to Culex quinquefasciatus

采用常规的生物测定方法确定了纯化的球形芽孢杆菌(Bacillus sphaericus)的缺失信号肽的97kDa营养期杀蚊毒素(Mosquitocidal toxin 1,Mtx1)蛋白和苏云金芽孢杆菌(Bacillus thuringiensis)27.3kDa的Cyt1Aa晶体蛋白对致倦库蚊(Culex quinquefasciatus)幼虫的杀虫活性。结果表明Mtx1和Cyt1Aa不同比例的混合物对致倦库蚊的毒力比单独毒素蛋白高,经统计分析表明两毒素蛋白对目标蚊幼虫具有明显的协同作用。在LC98处理浓度下,Mtx1和Cyt1Aa按3∶1混合的混合物LT50值比单独Mtx1的提前了6.36h。表明Cyt1Aa和Mtx1对致倦库蚊具有协同毒杀作用,提高对目标蚊虫的毒力、缩短半致死时间。该结果为深入研究Mtx1和Cyt1Aa的杀蚊作用方式奠定了基础,同时为其在蚊虫防治中的应用提供了新的思路和方法。

Mosquitocidal toxin 1 （Mtx1） was synthesized during vegetative phase of Bacillus sphaericus and it had been proved to have higher activity to Aedes spp. larvae and Binary toxin （Bin） resistance Culex larvae. The truncated 97kDa Mtxl with a deletion of the signal peptide and the CytlAa crystal protein, a 27.3kDa δ endotoxin from Bacillus thuringiensis subsp, israelensis （Bti）, were purified from Escherichia coli and B. thuringiensis recombinant strains respectively. Both purified toxins had high toxicity against Culex quinquefasciatus larvae. Bioassay result revealed the purified Mtxl toxin had high toxicity against the target mosquito larvae, with LC50 of 45.2ng/mL. However, the mixture of Mtx1 and Cyt1Aa exhibited higher toxicity against the mosquito larvae, with a lowest LC50 value of 20.19ng/mL at the ratio of 1：3. （Mtxl ：Cyt1 Aa）. The calculated synergistic factor of different mixtures suggested a strong synergistic effect between CytlAa toxin and Mtx1. Furthermore, the presence of CytlAa in the mixture could induce early larval mortality, enhancing the activity of Mtx1 to the target mosquito larvae. The synergistic effect of CytlAa on mortality of Mtxl to mosquito larvae might be caused by the damage of the larval midgut-hemocoel barrier induced by the activated Cyt1Aa toxin, which enhanced the specific pathogenesis of Mtx1 on mosquito larvae. It is suggested that the co-application of Mtx1 and CytlAa in future will be integrated for mosquito management.