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

University Of Alaska Fairbanks Campus, Fairbanks AK

Investigators

Abstract

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.