Effects Of Two Insecticides On The Gut Microbiota Of Insects Defoliating Ulmus Trees

Ulmus has high economic and ecological value.The outbreak of leaf-eating pests seriously would affects the growht of Ulmus,and the widespread existence of insect resistance limits the effectiveness of chemical control severely.Insect gut microbes can have important effects on host growth,reproduction,behavior,and various physiological and biochemical reactions.They also play a role in the process of host resistance.In this dissertation,using amplicon sequencing technology to study the differences in intestinal microbial community structure of 4 species of leaf-eating pests of Ulmus,and to explore the factors affecting the intestinal microbial community structure and function.The effects of 2 common insecticides,?-cypermethrin and phoxim,on the intestinal microbial community of insects were studied in order to reveal the role of intestinal microorganisms in the process of overcoming insecticide stress.The main results are as follows:1.The feeding patterns of host insects affect the community structure and function of intestinal bacteria of Ulmus leaf-eating pests.2.The host developmental stage affects the community structure and function by affecting the distribution of intestinal bacteria of Ulmus leaf-eating insects in different genus.There is a single dominant genus in imago and multiple dominant genus in larva.The taxonomic status of the host also affects the community structure and function of the intestinal bacteria.Host food habits have a greater effect on the structure of the intestinal bacterial community and a smaller effect on its function.3.The intestinal fungi of Ulmus leaf-eating insects are greatly affected by the host's food habits and developmental stage.Their dominant genus is Malassezia.4.Insecticide treatment can cause the abundance of sensitive bacteria in insect intestinal bacteria to decrease or even disappear,reducing the ability of the intestinal bacteria to metabolize amino acids and other substances.5.Intestinal bacteria promote the elimination of ?-cypermethrin mainly by enhancing transport capacity and synthesizing transporters such as ABC transporters,and repair and renew the damaged cells to correspond phoxim stress.The intestinal bacteria of Pyrrhalta aenescens larvae can repair cell damage caused by 2 insecticides,?-cypermethrin and phoxim.The intestinal bacteria of Ambrostoma quadriimpressum can synthesize CarE and GST to degrade ?-cypermethrin.6.The intestinal bacteria of A.quadriimpressum participate in the metabolism of ?-cypermethrin by the three drug metabolism pathways of the host,azathioprine and 6-thiopurine,fluorouracil and isoniazid.The up-regulation of CAT and GST activities in insect intestines can be attributed to intestinal bacteria,and insects may respond to ?-cypermethrin stress mainly with CYP450,CarE,etc.7.When the A.quadriimpressum has been treated by ?-cypermethrin for 5 days,the protein digestion and absorption ability of host increase,and its intestinal bacteria's ability to metabolize amino acids decrease,which is beneficial to the host insect to repair cells and synthesize detoxifying enzymes.It is more likely that drug metabolism is dominated by purple elm.In this experiment,the intestinal microbial diversity of various Ulmus leaf-eating insects and the effects of two different insecticides on intestinal bacteria were compared and analyzed.The effect of beta-cypermethrin on the digestive function and metabolic resistance of insect intestines was analyzed by taking A.quadriimpressum as an example to analyze how gut bacteria mediate insect resistance.It provides new research ideas for the research on the interaction between intestinal bacteria and hosts,and has important significance for the monitoring and control of leaf-eating pests.