Characterization of larval gut microbiota of two endoparasitoid wasps associated with their common host, <i>Plutella xylostella</i> (Linnaeus) (Lepidoptera: Plutellidae)

Insect gut microbes play important roles in digestion, metabolism, development, and environmental adaptation. Parasitoid wasps are one of the most important biological control agents in pest control, while the gut microbial species compositions and the associated functions have been poorly investigated. Two endoparasitoid wasps, <i>Cotesia vestalis</i> and <i>Diadromus collaris</i>, parasitize the larval stage and pupal stage of the diamondback moth, <i>Plutella xylostella</i>, respectively. Using whole-genome shotgun metagenomic sequencing, we characterized the gut microbial composition, diversity, and potential functional roles associated with the two parasitoid wasp larvae. The results reveal that Proteobacteria and Firmicutes are the dominant phyla in the gut of <i>C. vestalis</i> and <i>D. collaris</i> larvae, with <i>Rhizobium</i> and <i>Enterococcus</i> being the dominant genera. The putative microbial functions associated with the two parasitoid wasps might play a virtual role in assisting in consuming the host's nutritional composition. The enriched CAZymes family genes are primarily involved in the degradation and synthesis of chitin. Despite the richness of microbial species and communities, the microbes species and the microbial community structure exhibit significant similarity between the two parasitoid wasps and between the parasitoid wasp and the host <i>P. xylostella</i>. Notably, the prevalence of the genus <i>Enterococcus</i> shared among them suggests a possible link of gut microbes between the host and their associated parasitoids. Our study offers insights into the gut microbe-based interactions between the host and parasitoid wasps for the first time, potentially paving the way for the development of an ecologically friendly biocontrol strategy against the pest <i>P. xylostella</i>.IMPORTANCEEndoparasitoid wasps spend the majority of their lifespan within their host and heavily rely on the host's nutrition for survival. There is limited understanding regarding the composition and physiological impacts of gut microbial communities in parasitoid wasps, particularly during the larval stage, which is directly linked to the host. Based on a thorough characterization of the gut microbe and comprehensive comparative analysis, we found the microbial species of the larval parasitoid wasp <i>Cotesia vestalis</i> and the pupal parasitoid wasp <i>Diadromus collaris</i> were similar, sharing 159 genera and 277 species, as were the microbial community structure. Certain of the dominant microbial strains of the two parasitoid wasps were similar to that of their host <i>Plutella xylostella</i> larvae, revealing host insect may affect the microbial community of the parasitoid wasps. The putative microbial functions associated with the parasitoid wasp larvae play an important role in dietary consumption.