Dual oxidase gene Duox and Toll-like receptor 3 gene TLR3 in the Toll pathway suppress zoonotic pathogens through regulating the intestinal bacterial community homeostasis in Hermetia illucens L.

Black soldier fly (BSF; Hermetia illucens L.) larvae can convert fresh pig manure into protein and fat-rich biomass, which can then be used as livestock feed. Currently, it is the only insect approved for such purposes in Europe, Canada, and the USA. Pig manure is rich in zoonotic pathogens (e.g., Staphylococcus aureus and Salmonella spp.). BSF larvae inhibit these zoonotic pathogens; however, the mechanism is unclear. We employed RNAi, qRT-PCR, and Illumina MiSeq bacterial 16S rDNA high-throughput sequencing molecular techniques to study the interaction between the two immune genes (Duoxin Duox-reactive oxygen species [ROS] immune system and TLR3 in the Toll signaling pathway) and zoonotic pathogens to determine the mechanisms resulting in pathogen suppression. Results indicated that Bsf Duox-TLR3 RNAi increased bacterial load but decreased the relative abundance of Providenciaand Dysgonomonasintestinal symbionts. Concurrently, Bsf Duox-TLR3 RNAi inactivated the NF-κB signaling pathway, downregulated the expression of antimicrobial peptides, and diminished inhibitory effects on zoonotic pathogen. The resulting dysbiosis stimulated an immune response by activating BsfDuox and promoting ROS, which regulated the composition and structure of the gut bacterial community. Thus, BsfDuox and BsfTLR3 are important factors in regulating the gut key bacteria Providenciaand Dysgonomonas homeostasis while inhibiting target zoonotic pathogens.