球形芽孢杆菌杀蚊毒素的作用方式和蚊虫的抗性特征

球形芽孢杆菌（Bacillussphaericus）是一种对蚊幼虫有毒杀作用的好气芽孢杆菌。高毒力菌株在芽孢形成过程中能产生有51．4和41．9kDa蛋白组成的伴孢晶体。蚊幼虫取食芽孢／晶体混合物后，晶体蛋白被降解形成活性蛋白而结合到中肠上皮细胞的特异性结合位点上，最后导致蚊幼虫死亡；低毒力菌株和部分高毒力菌株在其营养体生长阶段可产生可溶性的100、30．5和38．5kDa的Mix毒素（Mtx1、Mtx2和Mix3）。该毒素同晶体毒素和其它杀虫毒素无同源性，其杀蚊作用机理不详。在实验室和野外长期高选择性压力下，蚊幼虫会通过中肠上皮细胞二元毒素特异性结合位点的改变而对球形芽孢杆菌产生不同水平的抗性，其抗性特性是由位于染色体上的单一隐性基因决定的。本文简述了球形芽孢杆菌的杀蚊毒素的作用方式及抗性蚊虫的抗性特性。

MODE OF ACTION OF BACILLUS SPHAERICUS MOSQUITOCIDAL TOXINS AND RESISTANCE OF MOSQUITOES: A REVIEW

Bacillus sphaericus is an aerobic, cosmopolitan and spore--forming bacteriawhich shows various toxicities against different mosquito species. All high toxicitystrains can produce 51. 2 and 41. 9kDa peptides assembling in a crystal form within sporangium during sporulation. After ingestion by mosquito larvae, the crystal dissolvesand is activated and causes death of the host. During its vegetative growth, some highand low-toxicity strains could also synthesize the mosquitocidal toxins(Mtx1,Mtx2 andMix3). These toxins can be broken down and be inactivited by the proteinases in media. Currently the mechanism of action of Mix is still nuclear. With continuous high selective pressure, mosquito larvae could develop different levels of resistance under thelaboratory and field conditions. It has been proved that development of resistance is resulted from the alteration of specific receptors on midgut brush-border membrane fragment and the characteristics are resistance determined by recessive genes. In addition,the strategy of the resistant larvae control is discussed in this review.