A novel detoxification strategy of Bombyx mori (Lepidoptera: Bombycidae) to dimethoate based on gut microbiota research

Bombyx mori (L.) (Lepidoptera: Bombycidae) is an important economic insect, and Exorista sorbillans (W.) (Diptera: Tachinidae) is an endoparasitic pest of larval B. mori. Dimethoate is less toxic to B. mori than E. sorbillans and is used in sericulture to controlling E. sorbillans. To investigate the effects of dimethoate treatment on the gut microorganisms and physiological functions of B. mori, 16S rRNA sequencing was used to analyzed the composition and structure of the gut microbiota. This study investigated their role in enhancing silkworm resistance by screening dominant populations after dimethoate treatment. The results indicated that dimethoate did not alter the composition of the dominant gut bacterial groups in silkworm; however, it significantly increased the abundance of the gut bacteria Methylobacterium and Aureimonas, and decreased the abundance of Enterobacterales, Bifidobacterium, Blautia, Collinsella, Faecalibacterium, and Prevotella. Eleven strains of dimethoate-resistant bacteria were selected through in vitro culture, all of which were unable to grow when dimethoate was used as a carbon source. Additionally, a germ-free silkworm model was established to assess detoxifying enzyme activity in the midgut. The results revealed that the gut symbiotic microbiota can enhance dimethoate resistance by increasing detoxification enzyme activity. This study identifies a novel pathway for silkworm resistance to dimethoate based on gut microbiota, providing new insights into the role of symbiotic gut bacteria in insecticide metabolism.