Department of Molecular Biology and Biochemistry, University of California, Irvine, CA 92697, USA.
Department of Entomology, University of California, Riverside, CA 92521, USA.
Proc Biol Sci. 2020 Oct 28;287(1937):20200980. doi: 10.1098/rspb.2020.0980.
Bumblebees ( spp.) are important and widespread insect pollinators, but the act of foraging on flowers can expose them to harmful pesticides and chemicals such as oxidizers and heavy metals. How these compounds directly influence bee survival and indirectly affect bee health via the gut microbiome is largely unknown. As toxicants in floral nectar and pollen take many forms, we explored the genomes of bee-associated microbes for their potential to detoxify cadmium, copper, selenate, the neonicotinoid pesticide imidacloprid, and hydrogen peroxide-which have all been identified in floral nectar and pollen. We then exposed workers to varying concentrations of these chemicals via their diet and assayed direct effects on bee survival. Using field-realistic doses, we further explored the indirect effects on bee microbiomes. We found multiple putative genes in core gut microbes that may aid in detoxifying harmful chemicals. We also found that while the chemicals are largely toxic at levels within and above field-realistic concentrations, the field-realistic concentrations-except for imidacloprid-altered the composition of the bee microbiome, potentially causing gut dysbiosis. Overall, our study shows that chemicals found in floral nectar and pollen can cause bee mortality, and likely have indirect, deleterious effects on bee health via their influence on the bee microbiome.
大黄蜂（ spp.）是重要且广泛分布的传粉昆虫，但在花朵上觅食的行为会使它们暴露在有害的农药和化学物质（如氧化剂和重金属）中。这些化合物如何直接影响蜜蜂的生存以及如何通过肠道微生物组间接影响蜜蜂的健康，在很大程度上尚不清楚。由于花蜜和花粉中的有毒物质有多种形式，我们探索了与蜜蜂相关的微生物的基因组，以研究它们潜在的解毒能力，包括镉、铜、硒酸盐、新烟碱类杀虫剂吡虫啉和过氧化氢——这些物质都已在花蜜和花粉中被鉴定出。然后，我们通过饮食让工蜂接触不同浓度的这些化学物质，并检测它们对蜜蜂生存的直接影响。使用具有田间实际意义的剂量，我们进一步探索了这些化学物质对蜜蜂微生物组的间接影响。我们在核心肠道微生物中发现了多个可能有助于解毒有害化学物质的假定基因。我们还发现，虽然这些化学物质在田间实际浓度和高于田间实际浓度的水平下大都具有毒性，但除吡虫啉外，这些具有田间实际意义的浓度会改变蜜蜂微生物组的组成，可能导致肠道菌群失调。总的来说，我们的研究表明，花蜜和花粉中的化学物质会导致蜜蜂死亡，并且可能通过对蜜蜂微生物组的影响间接对蜜蜂健康产生有害影响。
