| Spodoptera frugiperda has become an important pest in agricultural production in China.It has a wide range of hosts,endangers a variety of crops and causes major economic losses.Host plants are an important factor affecting insect gut microbes,and there are few studies on gut microbes of S.frugiperda.Due to the interaction between insects and intestinal microorganisms,intestinal microorganisms also affect the growth and development of insects.Thus,16 S r DNA and ITS high-throughput sequencing technologies were used to investigate the gut microbe diversity of S.frugiperda fed on different host plants.At the same time,antibiotics were used to change the structure of the intestinal microbial community,and the effects of intestinal microorganisms on the growth of host and the content of nutrients in hemolymph.To provide theoretical basis for studies on S.frugiperda host adaptability and intestinal microorganism on its growth and development.The results as follows:1.Analysis of intestinal microbial diversity of S.frugiperda feeding on different hostsThe intestinal microbes of S.frugiperda fed Zea mays,Triticum aestivum and Veronica polita were discovered in this study.The results show that the diversity of gut bacterial communities of S.frugiperda fed on T.aestivum was the highest,the diversity of intestinal fungal community of S.frugiperda fed on V.polita was the highest,and the richness of intestinal bacterial and fungal community of S.frugiperda fed on V.polita was the highest.At phylum level,Firmicutes,Actinobacteriota,and Proteobacteria were the dominant intestine bacteria while Ascomycota and Basidiomycota were the dominant intestinal fungal when Z.mays and T.aestivum were fed.Firmicutes and Actinobacteriota were the dominant intestine bacteria and Ascomycota was the dominant intestinal fungus when V.polita was fed.At genus level,when feeding on Z.mays,T.aestivum and V.polita,the abundance of Enterococcus was the highest.The highest abundance intestinal fungi in S.frugiperda fed on Z.mays,T.aestivum and V.polita was the highest,which was in the Trichosporon,unclassified Saccharomycetales and unclassified Dipodascaceae.The intestinal bacterial and fungal functions of S.frugiperda were predicted.The bacterial function was mainly involved in the metabolic process of the host,and the fungal function was mainly related to the basic metabolism or physiological function of the host.2.Antibiotic screening and determination of concentrationA total of 12 kinds of antibiotics were selected for the susceptibility test,and the size of inhibition zone was compared.The results showed that the intestinal bacteria of S.frugiperda were most sensitive to ciprofloxacin,and the diameter of inhibition zone was the largest.The minimum inhibitory concentration of ciprofloxacin against the intestinal bacteria of S.frugiperda was 1 μg/m L determined by micro broth method.3.Effect of antibiotics on intestinal microbial community structure of S.frugiperdaAfter antibiotic exposure,abundance of dominant bacteria in intestinal tract of S.frugiperda decreased significantly.The abundance of Firmicutes decreased from 75.43% to 20.78%.The abundance of Enterococcus decreased from 70.86% to 13.27%.Changes in bacterial community structure also affect fungal community structure.In intestinal fungi,the abundance of Basidiomycota increased from 57.70% to 79.56%,and the abundance of Ascomycota decreased from 41.45% to 20.43%.At the genus level,the abundance of Trichosporon increased,while the abundance of other fungi were decreased.As a result of functional prediction,the abundance of bacteria associated with carbohydrate metabolic pathways was dramatically reduced,while the abundance of fungi associated with various enzymes and metabolic pathways in the host changed.4.Effects of changes in intestinal microbial community structure on growth,development and nutritional metabolismAfter changes in intestinal microbial community structure,the larval and pupal stages of S.frugiperda were prolonged,the pupal weight was reduced.The contents of glucose,albumin and triglyceride in hemolymph were significantly reduced. |
