SGER: Stable Isotope Fingerprinting: A Novel Approach to Identifying Amino Acid Biosynthetic Sources, Using Stable Isotope Variation Among Amino Acids.

了解营养物质的流动是生物生物学和生态系统生态学的中心目标。例如，在营养生理学方面，研究人员刚刚开始认识到动物如何满足必需氨基酸和脂肪酸需求的复杂性，以及满足这些需求如何产生生理上的相互依赖。在北极生态系统中，氨基酸是北方植物群落的关键氮源，但它们如何提供给土壤尚不清楚。植物和根真菌(菌根)之间的营养联系是常见的，但伙伴之间营养交换的细节还不是很清楚。在所有这些情况下，可用于追踪养分交换的工具限制了进展。这项研究开发了一种新的方法来追踪氨基酸的生物合成来源，利用生物代谢在氨基酸的碳同位素特征中产生的变化。这些同位素特征可以被认为是生物合成的“指纹”，这些指纹可能是产生它们的有机体类型的诊断。这项拟议的研究将描述选定的微生物、植物和真菌的氨基酸同位素指纹。这些生物可以从头合成蛋白质中发现的所有20种氨基酸，并有可能为动物、土壤营养库或共生伙伴提供氨基酸。如果这些指纹被证明是生物合成来源的强大、可重现的指标，它们将改变研究人员解决现有技术无法回答的自然系统中营养物质流动问题的能力。这样的工具将对研究生理生态学、进化生态学、植物-昆虫相互作用、植物生物学、生态系统生态学和生物地球化学的科学家产生极大的兴趣。用来测量氨基酸中的同位素特征的分析正变得越来越可用。然而，缺乏比较数据导致了越来越多的文献充斥着验证不足的假设。因此，这项研究将极大地促进我们对氨基酸签名在生物体内和之间的可变性的理解，并将为具有广泛适用性的方法学提供基础。这项研究项目将包括对一名研究生进行开发这种新工具的培训。

Understanding nutrient flow is a central goal of both organismal biology and ecosystem ecology. In nutritional physiology, for example, researchers are only starting to appreciate the complexity of how animals meet requirements for essential amino acids and fatty acids, and how meeting those requirements can generate physiological interdependency. In arctic ecosystems, amino acids are a key source of nitrogen for boreal plant communities, but how they are supplied to soil is unclear. Nutritional associations between plants and root-fungi (mycorrhizae) are common, but the details of nutrient exchange between the partners are not well known. In all these cases, progress is limited by the available tools for tracing nutrient exchange. This research develops a new approach to tracing amino acid biosynthetic sources, using the variation generated by organismal metabolism in the carbon isotopic signatures of amino acids. These suites of isotopic signatures can be thought of as a biosynthetic "fingerprint," and these fingerprints may be diagnostic of the type of organism that produced them. The proposed research will characterize the amino acid isotopic fingerprints of select microorganisms, plants, and fungi. These organisms can synthesize de novo all twenty amino acids found in proteins, and potentially supply amino acids to animals, soil nutrient pools, or symbiotic partners. If these fingerprints prove to be robust, reproducible indicators of biosynthetic sources, they would transform the ability of researchers to address questions about nutrient flow in natural systems that cannot be answered with present technology. Such a tool will be of great interest to scientists studying physiological ecology, evolutionary ecology, plant-insect interactions, plant biology, ecosystem ecology, and biogeochemistry. The analyses used to measure isotope signatures in amino acids are becoming increasingly available. However, the lack of comparative data has contributed to a growing literature that is rife with poorly validated assumptions. Thus, this research will significantly advance our understanding of the variability of amino acid signatures within and among organisms, and will provide the foundation for a methodology with wide ranging applicability. This research project will involve training of a graduate student in the development of this novel tool.