苏云金芽胞杆菌JQD117菌株对韭蛆体内几种酶活性的影响

为明确苏云金芽胞杆菌JQD117对韭蛆幼虫蛋白酶和解毒酶活性的影响，测定比较了感染Bt后幼虫体内胰蛋白酶、胰凝乳蛋白酶、乙酰胆碱酯酶、谷胱甘肽-S-转移酶和羧酸酯酶的活性。首先采用室内生物活性测定方法明确了菌株JQD117对韭蛆3龄幼虫72 h的LC₅₀为2.8070×10⁷cfu/mL，然后采用10×LC₅₀、1×LC₅₀和0.1×LC₅₀三个浓度饲喂感染韭蛆幼虫，定期取样测定韭蛆体内5种酶活性，结果表明以较高浓度（1×LC₅₀和10×LC₅₀）感染韭蛆幼虫后体内蛋白酶和解毒酶活性变化较大，而以低浓度（0.1×LC₅₀）感染韭蛆幼虫后体内蛋白酶活性变化较小。其中，以1×LC₅₀和10×LC₅₀浓度感染韭蛆幼虫后，胰蛋白酶和乙酰胆碱酯酶活性在24~36 h和6~60 h与对照相比均显著升高；类胰凝乳蛋白酶和羧酸酯酶活性在6~60 h与对照相比均受到显著抑制。以0.1×LC₅₀浓度感染韭蛆幼虫后，胰蛋白酶活性只在36 h时与对照相比显著升高；乙酰胆碱酯酶活性在12~48 h时与对照相比显著升高；羧酸酯酶活性只在6 h与对照相比受到显著抑制；类胰凝乳蛋白酶活性与对照相比均无显著变化。谷胱甘肽-S-转移酶活性在三种感染浓度下与对照相比均无显著变化。可见，感染JQD117对韭蛆体内蛋白酶和解毒酶活性均产生了不同程度的影响，且随感染浓度的升高而增强，扰乱了韭蛆正常的生理代谢和对外源毒素的分解，本文为Bt防治韭蛆应用和开发提供了理论指导。

Effect of Bacillus thuringiensis JQD117 Strain on Intestinal Protease Activity of Larvae of Bradysia odoriphaga

Effect of Bacillus thuringiensis JQD117 strain on activities of protease and detoxification enzymes of Bradysia odoriphaga larvae, including trypsin, chymotrypsin, acetylcholinesterase (AchE), glutathione-S-transferase (GST), and carboxylesterase (CarE), were determined. The LC₅₀ of JQD117 strain to B. odoriphaga 3^rd instar larvae at 72 h post treatment was determined to be 2.8070×10⁷cfu/mL by laboratory bioactivity assay. Then 10×LC₅₀, 1×LC₅₀ and 0.1×LC₅₀ concentrations of JQD117 were used to feed and infect the B. odoriphaga 3^rd instar larvae. Activities of the five enzymes were measured to the samples regularly collected from the population. The results show that, when the B. odoriphaga 3^rd instar larvae were exposed to high concentrations (1×LC₅₀ and 10×LC₅₀) of JQD117, enzyme activities varied relatively widely. Among them, when the B. odoriphaga 3^rd instar larvae were infected with 1×LC₅₀ and 10×LC₅₀ concentrations of JQD117, trypsin and AchE activities increased significantly at 24-36 h and 6-60 h compared with the control group, while chymotrypsin and CarE activities were significantly inhibited at 6-60 h compared with the control group. When the B. odoriphaga 3^rd instar larvae were infected with 0.1×LC₅₀ concentrations of JQD117, activities of trypsin and AchE were significantly higher than that of the control group only at 36 h and at 12-48 h, respectively; CarE activity was significantly inhibited only at 6 h compared with that of the control group while no significant change in the activity of chymotrypsin was observed. There was no significant change in GST activity at the three infection concentrations compared with the control. Therefore, infection of JQD117 influences on protease and detoxification enzyme activity in B. odoriphaga larvae in a dose-dependent manner. The results provide a theoretical guidance for the application and development of Bt for control of B. odoriphaga.