Organophosphate insecticides that are heavily used in agriculture for pest control have caused growing environmental problems and public health concerns worldwide. Ironically, insecticide resistance develops quickly in major lepidopteran pests, partially via their microbial symbionts. To investigate the possible mechanisms by which the microbiota confers insecticide resistance to Lepidoptera, the model organism silkworm Bombyx mori (Lepidoptera: Bombycidae) was fed different antibiotics to induce gut dysbiosis (microbiota imbalance). Larvae treated with polymyxin showed a significantly lower survival rate when exposed to chlorpyrifos. Through high-throughput sequencing, we found that the abundances of Stenotrophomonas and Enterococcus spp. changed substantially after treatment. To assess the roles played by these two groups of bacteria in chlorpyrifos resistance, a germ-free (GF) silkworm rearing protocol was established to avoid the influence of natural microbiota and antibiotics. Monoassociation of GF silkworms with Stenotrophomonas enhanced host resistance to chlorpyrifos, but not in Enterococcus-fed larvae, consistent with larval detoxification activity. GC-μECD detection of chlorpyrifos residues in feces indicated that neither Stenotrophomonas nor Enterococcus degraded chlorpyrifos directly in the gut. However, gut metabolomics analysis revealed a highly species-specific pattern, with higher levels of essential amino acid produced in the gut of silkworm larvae monoassociated with Stenotrophomonas. This critical nutrient provisioning significantly increased host fitness and thereby allowed larvae to circumvent the deleterious effects of these toxic chemicals more efficiently. Altogether, our study not only suggests a new mechanism for insecticide resistance in notorious lepidopteran pests but also provides a useful template for investigating the interplay between host and gut bacteria in complex environmental systems.

在农业中大量用于控制害虫的有机磷杀虫剂已引起全球范围内日益严重的环境问题和公共卫生问题。具有讽刺意味的是，在主要鳞翅目害虫中，部分通过微生物共生体对杀虫剂产生了快速的抗药性。为了研究微生物群赋予鳞翅目杀虫剂抗药性的可能机制，向模型生物蚕Bombyx mori（鳞翅目：Bombycidae）饲喂了不同的抗生素，以诱导肠道营养不良（微生物群失衡）。当暴露于毒死rif时，用多粘菌素处理的幼虫存活率明显降低。通过高通量测序，我们发现嗜麦芽窄食单胞菌和肠球菌的丰度spp。治疗后变化很大。为了评估这两类细菌在毒死rif抗性中的作用，建立了无菌（GF）蚕饲养规程，以避免自然微生物群和抗生素的影响。GF蚕与嗜麦芽单胞菌的单缔合增强了宿主对毒死rif的抗性，但在肠球菌喂养的幼虫中却没有，这与幼虫的解毒活性一致。GC-μECD检测粪便中毒死rif残留，表明嗜麦芽窄食单胞菌和肠球菌均无直接在肠道中降解毒死rif。然而，肠道代谢组学分析显示了一种高度特定物种的模式，与单核嗜单胞菌单联的家蚕幼虫的肠道中产生了更高水平的必需氨基酸。这种至关重要的营养供应大大提高了宿主的适应能力，从而使幼虫更有效地规避了这些有毒化学物质的有害作用。总而言之，我们的研究不仅提出了臭名昭著的鳞翅目害虫抗药性的新机制，而且为研究复杂环境系统中宿主与肠道细菌之间的相互作用提供了有用的模板。