中肠共生菌嗜水气单胞菌对淡色库蚊溴氰菊酯抗性的影响

Effect of the midgut symbiotic Aeromonas hydrophila on the deltamethrin resistance of Culex pipiens pallens

目的探究中肠共生菌嗜水气单胞菌(Aeromonas hydrophila)与淡色库蚊对溴氰菊酯抗性之间的关系。方法测定淡色库蚊敏感品系与抗性品系中肠中嗜水气单胞菌相对丰度;分离培养抗性蚊中肠内嗜水气单胞菌,对敏感品系蚊虫进行嗜水气单胞菌口饲添加,抗性品系口饲抗生素消除及消除后回饲,然后进行CDC Bottle抗性测定和细胞色素酶P450(P450s)活性测定。结果嗜水气单胞菌在抗性蚊中肠中的丰度显著高于敏感蚊(P<0.05)。CDC Bottle试验显示,接触溴氰菊酯120 min时敏感品系增菌组的抗药性是对照组的2.41倍,抗性显著提升;口饲抗生素的抗性品系消除组的抗药性降低至对照组的66%,抗药性有所下降;嗜水气单胞菌回饲后抗性回升至消除组的1.71倍。敏感品系添加嗜水气单胞菌后P450s活性水平提高到对照组的2.05倍;消除抗性品系蚊肠道内嗜水气单胞菌后P450s活性水平降低至对照组的58%;回饲组P450s活性提高至消除组的2.13倍。结论蚊中肠共生菌嗜水气单胞菌可通过提高蚊体内外源物质代谢酶的活性介导蚊对溴氰菊酯的抗性,这为针对蚊杀虫剂抗性产生机制的研究及蚊害的综合性治理提供了一个新的思路。

Objective To explore the role of the midgut symbiotic bacterium Aeromonas hydrophila in the resistance of Culex pipiens pallens to deltamethrin.Methods The relative abundance of A.hydrophila in the midgut of different strains(deltamethrin-susceptible strains and deltamethrin-resistant strains)was measured using qPCR.A.hydrophila in the midgut of resistant mosquitoes was isolated and cultured.Sensitive strains were orally fed A.hydrophila.Resistant strains were fed antibiotics to eliminate A.hydrophila and then fed A.hydrophila again after elimination.Then CDC bottle bioassay was performed and cytochrome P450(P450)activity was determined.Results A.hydrophila was significantly more abundant in the midgut of resistant mosquitoes compared to sensitive mosquitoes(t=3.100,P<0.05).The CDC bottle bioassay indicated that the resistance of the orally fed strain was 2.41 times that of the un-fed control(P<0.001).The resistance of mosquitoes from which A.hydrophila had been eliminated decreased to 0.66 times of the control(P<0.001).After mosquitoes were fed A.hydrophila again,resistance increased to 1.71 times that in mosquitoes from which A.hydrophila had been eliminated(P<0.001).After mosquitoes were orally fed A.hydrophila,the level of P450 activity increased to 2.05 times that in the sensitive strain(t=5.914,P<0.0001).After elimination of A.hydrophila,the level of P450 activity decreased to 0.58 times that in the control group(t=5.508,P<0.05),and the level of P450 activity in mosquitoes fed A.hydrophila again increased to 2.13 times that in mosquitoes from which A.hydrophila had been eliminated(t=7.883,P<0.05).Conclusion A.hydrophila,a midgut commensal bacterium,can mediate mosquito resistance to deltamethrin by increasing the activity of metabolic enzymes of exogenous substances in mosquitoes.This result provides new approaches to further research on the mechanism of insecticide resistance and the comprehensive control of mosquito-borne diseases.