Collaborative Research: Mechanism of protective symbiosis in the honey bee

每三口食物中就有一口是由蜜蜂授粉的。蜜蜂是美国最重要的农业授粉者，每年为美国农作物增加200亿美元的价值。 然而，蜜蜂的数量正在下降，部分原因是害虫和病原体。 事实上，真菌病原体微孢子虫在美国农业部导致蜜蜂群体下降的压力源列表中仅次于瓦螨（美国农业部蜜蜂殖民地调查，2018年8月）。如果没有蜜蜂，大部分农业经济将出现产量下降。再加上气候变化，这种生产力的损失将对养活美国公民的能力产生复合影响。因此，需要新的技术创新来帮助缓解蜂群的下降。这项研究将调查一种新的蜜蜂抗真菌共生体，确定它如何保护蜜蜂，以及它到底产生什么抗真菌。除了对蜜蜂的好处外，新型抗真菌药物的发现还可能在对抗真菌病原体方面对人类健康产生下游效益，从而有助于生物经济。 该项目还支持研究生的培训。 因此，这将支持下一代科学家的教育，他们最终将在新的生物经济中工作。这项研究的目标是确定蜜蜂共生体如何保护蜜蜂幼虫免受真菌病原体的侵害。蜜蜂数量的急剧下降可能是由于环境压力，包括有限的花卉资源（营养压力），病原体（免疫压力），以及暴露于杀真菌剂和杀虫剂（化学压力）。这里显示的数据发现，蜜蜂的细菌共生体可以保护蜜蜂免受这些重要压力之一：真菌病原体。初步数据表明，共生体分泌的抗真菌代谢产物（S），保护蜜蜂育雏污垢，在体外试验和幼虫感染实验支持这一结论。该项目旨在描述这种共生体如何保护蜜蜂。这种特性是如何在蜜蜂相关和花相关的α-变形菌的进化史上进化的？抗真菌代谢物的身份是什么？申请人将使用微生物测定、体外蜜蜂饲养、遗传学、基因组学和化学的组合来回答这些问题。这是第一次探索蜜蜂中抗真菌共生体的共生机制，并将使生物学家能够确定蜜蜂微生物组的特定成员如何影响育雏健康。此外，由于这种共生体与那些与野生蜜蜂和花相关的共生体有关，因此它提供了一个理想的模型来探索共生体中宿主有益性状的选择和维持。更广泛的影响包括研究生的研究培训，以及在两个机构为本科生创建研究体验计划。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

One out of every 3 mouthfuls of food consumed was pollinated by a bee. The honey bee is the most important agricultural pollinator in the US, adding $20 billion to the value of US crops annually. However, populations of honey bees are in decline due, in part, to pests and pathogens. In fact, the fungal pathogen Nosema is only second to the Varroa mite in the USDA list of stressors contributing to colony decline of honey bees (USDA Honey Bee Colonies survey, August, 2018). Without honey bees, large swathes of the agricultural economy would see declines in production. Combined with climate change, this loss in productivity will have a compounding effect on the ability to feed US citizens. Therefore, new technological innovations are needed to help mitigate the decline of honey bee colonies. This research will investigate a novel anti-fungal symbiont of honey bees, identify how it protects bees, and exactly what anti-fungal it produces. In addition to the benefits to bees, the discovery of novel anti-fungals may also have downstream benefits for human health in the fight against fungal pathogens, thus helping the bioeconomy. This project also supports the training of graduate students. Thus, this will support the education of the next generation of scientists who would ultimately work in the new bioeconomy.The goal of this research is to identify how a honey bee symbiont protects brood, honey bee larvae, from fungal pathogens. The dramatic decline of the honey bee population is likely due to environmental stressors including limited floral resources (nutritional stress), pathogens (immune stress), and exposure to fungicides and pesticides (chemical stress). Data shown here discovered that a bacterial symbiont of honey bees protects against one of these significant stressors: fungal pathogens. Preliminary data suggest that the symbiont secretes anti-fungal metabolite(s) that protects bee brood from fouling; both in vitro assays and larval infection experiments support this conclusion. This project aims to characterize how this symbiont protects bees. How did this trait evolve across the phylogeny of bee-associated and flower-associated alphaproteobacteria? And what is the identity of the antifungal metabolite? Applicants will use a combination of microbial assays, in vitro bee rearing, genetics, genomics, and chemistry to answer these questions. This is the first time that the mechanism of symbiosis for an anti-fungal symbiont in bees has been explored, and will allow biologists to identify how specific members of the honey bee microbiome affect brood health. Additionally, because this symbiont is related to those found associated with wild bees and flowers, it presents an ideal model in which to explore the selection and maintenance in a symbiont, of a host-beneficial trait. Broader impacts include research training for graduate students, and creating a research experience program for undergraduate students at two institutions.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.