Amino acids are the primary nitrogen-containing compounds in cells, participating in various metabolic processes such as protein synthesis and degradation into other nitrogenous compounds. Compound-specific nitrogen isotope analysis of amino acids in environmental samples can provide insight into nitrogen sources, cycling, and tropic modifications in ecosystems. However, we lack comprehensive understanding of N utilization patterns in microorganisms, which are the site of nitrogen assimilation in biological systems, due to the varied and complex mechanisms by which microbes can acquire and metabolize nitrogen-containing compounds. δ15N measurements for free intracellular amino acids and protein-bound amino acids for environmentally-relevant microbial groups may aid in untangling the biochemical processes involved in amino acid metabolism performed by these microbial communities. Here, we report intracellular amino acid δ15N values for R. palustris, a metabolically versatile anoxygenic phototrophic bacterium.
