Collaborative Research: The brood cell microbiome of solitary bees: origin, diversity, function, and vulnerability

蜜蜂是全世界开花植物最重要的传粉者。在地球上325,000种开花植物中，超过85%依靠动物授粉，而绝大多数授粉是由蜜蜂进行的。据估计，每年蜜蜂对美国农作物产量的贡献为150亿美元，对全球作物产量的贡献为1700亿美元。高价值的蜜蜂授粉作物包括苹果和其他早春树上的水果、草莓、蓝莓、樱桃、小红莓、南瓜和南瓜、西红柿、杏仁和许多其他水果。美国农业生产的经济可行性取决于稳定和健康的野生和驯化蜜蜂种群。然而，蜜蜂种群受到各种因素的威胁，包括栖息地丧失、病原体溢出、入侵动植物和使用杀虫剂，这些因素可能扰乱蜜蜂幼虫发育所必需的正常微生物共生体(“育苗细胞”微生物群)。这项研究项目的重点是了解微生物在各种蜜蜂物种的幼虫营养中所起的作用。之前的研究已经记录了蜜蜂花粉和花蜜饮食中细菌和酵母菌的多样性群落。当幼虫消耗这些花粉/花蜜时，它们正在摄取微生物，我们的初步结果表明，这些微生物构成了幼虫饮食的重要组成部分。这个项目有可能显著改变我们对蜜蜂和开花植物之间1.2亿年合作关系的看法，并将为发展长期的蜜蜂保护努力提供必要的信息。项目外展工作包括为K-12学生举办关于独居蜜蜂的教育活动，以及为广大受众提供蜜蜂-微生物-花卉互动互动示范。该项目将使用尖端方法(1)记录花卉和花粉中的微生物多样性，(2)确定微生物在幼虫发育和健康中的营养作用，以及(3)了解微生物群落的变化如何影响幼虫的发育。为了记录寄主植物花和花粉供应中的微生物多样性，研究小组将使用扩增子测序和微生物元基因组学。这些方法将记录花粉供应中存在的微生物种类，以及这些微生物在花粉成熟期间进行的代谢活动。筛选寄主植物物种的花粉和花蜜将为了解育苗细胞微生物群的来源提供关键的见解。为了确定微生物群落的营养作用，研究小组将使用营养生态学的两种方法：化合物特定同位素分析和中性脂肪脂肪酸分析。这些分析将使研究小组能够追踪15种蜜蜂幼虫饮食中氨基酸和脂肪酸的来源(花卉或微生物)。最后，通过操纵性实验室实验，研究小组将确定微生物群落的修改如何影响幼虫的发育。结合这些研究的结果，将全面了解蜜蜂和开花植物是如何通过它们共同的微生物伙伴相互作用的。该项目由系统学和生物多样性科学集群(环境生物学分部)和共生、防御和自我认可计划(综合组织系统分部)共同资助。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Bees are the single most important pollinators of flowering plants worldwide. Over 85% of the 325,000 flowering plant species on earth depend on animals for pollination, and the vast majority of pollination is carried out by bees. Annually, bees are estimated to contribute $15 billion to US crop production and $170 billion to global crop production. High-value bee-pollinated crops include apple and other early spring tree fruits, strawberries, blueberries, cherries, cranberries, squash and pumpkins, tomatoes, almonds, and many others. The economic viability of US agricultural production is dependent on stable and healthy wild and domesticated bee populations. However, bee populations are threatened by a variety of factors, including habitat loss, pathogen spillover, invasive plants and animals, and pesticide use, which can disrupt the normal microbial symbionts essential for bee larval development (the "brood cell" microbiome). This research project focuses on understanding what role microbes play in the larval nutrition in a wide variety of bee species. Previous research has documented a diverse community of bacteria and yeasts in the pollen and nectar diet of bees. As larvae consume these pollen/nectar provisions they are ingesting microbes, and our preliminary results indicate that these microbes form an essential component of the larval diet. This project has the potential to significantly modify how we view the 120 million-year-old partnership between bees and flowering plants, and will provide essential information for developing long-term bee conservation efforts. Project outreach efforts include educational activities on solitary bees for K-12 students and interactive demonstrations of bee-microbe-flower interactions for broad audiences. The project will use cutting-edge methods to (1) document the microbial diversity in flowers and pollen provisions, (2) determine the nutritional role of microbes in larval development and health, and (3) understand how alterations in microbial community impact larval development. To document microbial diversity in both host-plant flowers and pollen provisions, the research team will use amplicon sequencing and microbial metagenomics. These methods will document the microbial species present in pollen provisions as well as the metabolic activities these microbes perform during pollen maturation. Screening the pollen and nectar of host-plant species will provide key insights into the source of the brood cell microbiome. To determine the nutritional role of the microbial community the research team will use two methods from trophic ecology: compound specific isotope analysis and neutral lipid fatty acid analysis. These analyses will permit the research team to track the origin (floral or microbial) of amino acids and fatty acids in the larval diet of 15 focal bee species. Finally, through manipulative laboratory experiments the research team will determine how modifications of the microbial communities impact larval development. Combining the results of these studies will provide a comprehensive understanding of how bees and flowering plants interact via their shared microbial partners. This project is jointly funded by the Systematics and Biodiversity Sciences Cluster (Division of Environmental Biology) and the Symbiosis, Defense and Self-recognition Program (Division of Integrative Organismal Systems).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.