Honeybees are important pollinators, having an essential role in the ecology of natural and agricultural environments. Honeybee colony losses episodes reported worldwide and have been associated with different pests and pathogens, pesticide exposure, and nutritional stress. This nutritional stress is related to the increase in monoculture areas which leads to a reduction of pollen availability and diversity. In this study, we examined whether nutritional stress affects honeybee gut microbiota, bee immunity, and infection by Nosema ceranae, under laboratory conditions. Consumption of Eucalyptus grandis pollen was used as a nutritionally poor-quality diet to study nutritional stress, in contraposition to the consumption of polyfloral pollen. Honeybees feed with Eucalyptus grandis pollen showed a lower abundance of Lactobacillus mellifer and Lactobacillus apis (Firm-4 and Firm-5, respectively) and Bifidobacterium spp. and a higher abundance of Bartonella apis, than honeybees fed with polyfloral pollen. Besides the impact of nutritional stress on honeybee microbiota, it also decreased the expression levels of vitellogenin and genes associated to immunity (glucose oxidase, hymenoptaecin and lysozyme). Finally, Eucalyptus grandis pollen favored the multiplication of Nosema ceranae. These results show that nutritional stress impacts the honeybee gut microbiota, having consequences on honeybee immunity and pathogen development. Those results may be useful to understand the influence of modern agriculture on honeybee health.

蜜蜂是重要的传粉媒介，在自然和农业环境的生态中具有至关重要的作用。全世界都报道了蜜蜂群落的丧失事件，并与不同的病虫害和病原体，农药接触以及营养压力有关。这种营养压力与单一养殖面积的增加有关，导致花粉供应和多样性的减少。在这项研究中，我们检查了营养压力是否在实验室条件下影响蜜蜂肠道菌群，蜜蜂免疫力和菜豆的感染。食用桉树花粉作为营养不良的饮食来研究营养压力，与食用多花粉相反。蜜蜂喂桉树花粉显示出较低的丰度是产乳杆菌和apis（分别为Firm-4和Firm-5）和双歧杆菌属。和饲喂多花花粉的蜜蜂相比，Bartonella apis的丰度更高。除了营养压力对蜜蜂微生物群的影响外，它还降低了卵黄蛋白原蛋白的表达水平以及与免疫相关的基因（葡萄糖氧化酶，hymenoptaecin和溶菌酶）。最后，桉树花粉有利于Nosema ceranae的繁殖。这些结果表明营养压力影响蜜蜂肠道菌群，对蜜蜂免疫力和病原体发育产生影响。这些结果可能有助于理解现代农业对蜜蜂健康的影响。