Aly C, Mulla M S, Federici B A
J Invertebr Pathol. 1989 Jan;53(1):12-20. doi: 10.1016/0022-2011(89)90068-2.
Larvae of Culex quinquefasciatus are much more susceptible to the toxin of Bacillus sphaericus than are larvae of Aedes aegypti. In the present study, the rate of ingestion, dissolution, and the cleavage by midgut proteases of the B. sphaericus toxin were compared in larvae of these species to determine whether these factors account for the differences in susceptibility. During filter feeding, larvae of both species removed significant quantities of B. sphaericus toxin from suspensions. Filtration rates for 1 hr, the time at which C. quinquefasciatus exhibited marked intoxication, were higher for A. aegypti (576-713 microliters/larva/hr) than for C. quinquefasciatus (446-544 microliters/larva/hr). Within 24 hr of exposure, A. aegypti larvae ingested 97-99% of the toxin particulates and suffered not more than 10% mortality in suspensions which induced complete mortality in C. quinquefasciatus within 2 hr of exposure. Quantification of the particulate toxin present in larvae after exposure to B. sphaericus suspensions revealed that larvae of both species contained only minor amounts of the toxin, suggesting the larvae had been able to solubilize the toxin after ingestion. Proteases recovered from the feces of larvae cleaved at 43-kDa protein isolated from B. sphaericus toxin extract to 40 kDa in both species. Thus, differences in susceptibility to the B. sphaericus toxin between A. aegypti and C. quinquefasciatus are not due to differences in rates of ingestion, dissolution, or the specificity of proteases.
致倦库蚊幼虫比埃及伊蚊幼虫对球形芽孢杆菌的毒素更敏感。在本研究中，对这两种幼虫摄入、溶解球形芽孢杆菌毒素以及中肠蛋白酶对其裂解的速率进行了比较，以确定这些因素是否是敏感性差异的原因。在滤食过程中，两种幼虫都从悬浮液中去除了大量的球形芽孢杆菌毒素。埃及伊蚊在1小时（此时致倦库蚊表现出明显中毒症状）的过滤速率（576 - 713微升/幼虫/小时）高于致倦库蚊（446 - 544微升/幼虫/小时）。在接触毒素24小时内，埃及伊蚊幼虫摄入了97 - 99%的毒素颗粒，在悬浮液中的死亡率不超过10%，而相同悬浮液在接触2小时内可导致致倦库蚊完全死亡。对接触球形芽孢杆菌悬浮液后的幼虫体内的颗粒毒素进行定量分析发现，两种幼虫体内仅含有少量毒素，这表明幼虫在摄入毒素后能够将其溶解。从幼虫粪便中回收的蛋白酶可将从球形芽孢杆菌毒素提取物中分离出的43 kDa蛋白质裂解为40 kDa，两种幼虫均如此。因此，埃及伊蚊和致倦库蚊对球形芽孢杆菌毒素敏感性的差异并非由于摄入速率、溶解速率或蛋白酶特异性的不同。
