Multiple trophic pathways support fish on floodplains of California's Central Valley.

We used compound-specific isotope analysis of carbon isotopes in amino acids (AAs) to determine the biosynthetic source of AAs in fish from major tributaries to California's Sacramento-San Joaquin river delta (i.e., the Sacramento, Cosumnes and Mokelumne rivers).

Central Metabolism and Growth Rate Impacts on Hydrogen and Carbon Isotope Fractionation During Amino Acid Synthesis in .

Compound specific stable isotope analysis (CSIA) of amino acids from bacterial biomass is a newly emerging powerful tool for exploring central carbon metabolism pathways and fluxes. By comparing isotopic values and fractionations relative to water and growth substrate, the impact of variable flow path for metabolites through different central metabolic pathways, perturbations of these paths, and their resultant consequences on intracellular pools and resultant biomass may be elucidated. Here, we explore the effects that central carbon metabolism and growth rate can have on stable hydrogen (δH) and carbon (δC) compound specific isotopic values of amino acids, and whether diagnostic isotopic fingerprints are revealed by these paired analyses.

Compound-specific δH analysis highlights the relationship between direct assimilation and de novo synthesis of amino acids from food and water in a terrestrial mammalian omnivore.

Hydrogen isotope (δH) analysis has been routinely used as an ecological tracer for animal movement and migration, yet a biochemical understanding of how animals incorporate this element in the synthesis of tissues is poorly resolved. Here, we apply a new analytical tool, amino acid (AA) δH analysis, in a controlled setting to trace the influence of drinking water and dietary macromolecules on the hydrogen in muscle tissue. We varied the δH of drinking water and the proportions of dietary protein and carbohydrates with distinct hydrogen and carbon isotope compositions fed to house mice among nine treatments.