取食2种猎物的异色瓢虫幼虫肠道可培养细菌分离鉴定与促消化潜力分析OA

[Objective]This study aimed to isolate and identify culturable bacteria from the larval gut of Harmonia axyridis fed on two prey species,and to analyze their potential for promoting gut digestion.It provided theoretical support for the development and utilization of insect gut microbial resources,as well as for optimizing the application of Harmo-nia axyridis in biological control.[Method]Larvae of Harmonia axyridis fed on Aphis craccivora and Spodoptera litura larvae were taken as experimental materials.Culturable gut bacteria were isolated and purified by traditional isolation and culture methods.The isolated strains were identified by 16S rDNA sequence analysis,and selective media were used to screen strains capable of producing digestive enzymes including amylase,protease and lipase.[Result]A total of 18 bacte-rial strains belonging to 4 phyla,8 families,and 16 genera were isolated from the gut of Harmonia axyridis larvae fed on Aphis craccivora,including 12 strains of Proteobacteria,2 strains of Bacillota,2 strains of Actinobacteria,and 2 strains of Bacteroidetes.Six strains capable of producing digestive enzymes were screened out,namely Mammaliicoccus sciuri strain Q2,Serratia marcescens strain R2,Stenotrophomonas maltophilia strain R34,Staphylococcus xylosus strain Fm,Acinetobacter soli strain Q5 and Corynebacterium glycinophilum strain R9.Among them,Serratia marcescens strain R2 could produce both protease and lipase simultaneously.Six bacterial strains belonging to 2 phyla,3 families,and 5 genera were isolated from the gut of Harmonia axyridis larvae fed on Spodoptera litura larvae,consisting of 3 strains of Proteo-bacteria and 3 strains of Bacillota.Only one strain with digestive enzyme-producing capacity was obtained;it could pro-duce both protease and lipase and was identified as Serratia marcescens strain X7.No amylase-producing strains were screened from culturable gut bacteria of Harmonia axyridis larvae fed on the two prey species.[Conclusion]The species richness of culturable gut bacteria and digestive enzyme-producing strains in Harmonia axyridis larvae fed on Spodoptera litura larvae was markedly lower than that in larvae fed on Aphis craccivora,which may weaken their gut digestive func-tion.The results indicate that prey species can alter the diversity and function of gut microbiota in Harmonia axyridis lar-vae,thereby affecting their growth and development.