American foulbrood (AFB) disease and chalkbrood disease (CBD) are important bacterial and fungal diseases, respectively, that affect honeybee broods. Exposure to agrochemicals is an abiotic stressor that potentially weakens honeybee colonies. Gut microflora alterations in adult honeybees associated with these biotic and abiotic factors have been investigated. However, microbial compositions in AFB- and CBD-infected larvae and the profile of whole-body microbiota in foraging bees exposed to agrochemicals have not been fully studied. In this study, bacterial and fungal communities in healthy and diseased (AFB/CBD) honeybee larvae were characterized by amplicon sequencing of bacterial 16S rRNA gene and fungal internal transcribed spacer1 region, respectively. The bacterial and fungal communities in disordered foraging bees poisoned by agrochemicals were analysed. Our results revealed that healthy larvae were significantly enriched in bacterial genera Lactobacillus and Stenotrophomonas and the fungal genera Alternaria and Aspergillus. The enrichment of these microorganisms, which had antagonistic activities against the etiologic agents for AFB and CBD, respectively, may protect larvae from potential infection. In disordered foraging bees, the relative abundance of bacterial genus Gilliamella and fungal species Cystofilobasidium macerans were significantly reduced, which may compromise hosts' capacities in nutrient absorption and immune defence against pathogens. Significantly higher frequency of environmentally derived fungi was observed in disordered foraging bees, which reflected the perturbed microbiota communities of hosts. Results from PICRUSt and FUNGuild analyses revealed significant differences in gene clusters of bacterial communities and fungal function profiles. Overall, results of this study provide references for the composition and function of microbial communities in AFB- and CBD-infected honeybee larvae and foraging bees exposed to agrochemicals.

美国臭虫（AFB）病和白垩病（CBD）分别是重要的细菌和真菌病，它们会影响蜜蜂的繁殖。暴露于农药中是一种非生物胁迫源，可能削弱蜜蜂的菌落。已经研究了与这些生物和非生物因子相关的成年蜜蜂肠道菌群的变化。然而，尚未充分研究过AFB和CBD感染的幼虫中的微生物组成以及觅食蜂中暴露于农用化学品的全身微生物群的分布。在这项研究中，健康和患病（AFB / CBD）蜜蜂幼虫中的细菌和真菌群落分别通过细菌16S rRNA基因和真菌内部转录的spacer1区的扩增子测序来表征。分析了农用化学品中毒的无序觅食蜜蜂的细菌和真菌群落。我们的结果表明，健康的幼虫在细菌属中明显富集乳酸杆菌和嗜麦芽气单胞菌和真菌链格霉和曲霉。这些微生物的富集分别对AFB和CBD的病原体具有拮抗作用，可以保护幼虫免受潜在的感染。在无序觅食的蜜蜂中，细菌属Gilliamella和真菌物种Cyfifilobasidium macerans的相对丰度显着降低，这可能会损害宿主在营养吸收和抵抗病原体的免疫防御能力。在无序觅食的蜜蜂中观察到更高频率的环境衍生真菌，这反映了宿主微生物群落的扰动。PICRUSt和FUNGuild分析的结果表明，细菌群落和真菌功能谱的基因簇存在显着差异。总体而言，这项研究的结果为AFB和CBD感染的蜜蜂幼虫以及接触农药的蜜蜂觅食中微生物群落的组成和功能提供了参考。