In the marine environment, nitrogen often limits phytoplankton growth and influences microbial metabolism, community structure, and function. Microorganisms that rely on fixed nitrogen are likely switching between nitrogen sources frequently as local resources of preferred nitrogen compounds are depleted or replenished. Strains of the globally important picocyanobacteria Synechococcus have differing capability to use a variety of nitrogen sources, potentially contributing to their ubiquity. Our understanding of Synechococcus nitrogen use predominantly comes from laboratory studies that provide a single nitrogen substrate, thus there remain open questions associated with the metabolic effects of a switch between two nitrogen sources. To address these questions, we grew several strains of Synechococcus on a mixture of ammonium and nitrate and measured quantitative changes in protein abundance during the N-source switch from the former to the latter. Using ¹⁵N stable-isotope tracing proteomics, we determine which proteins are being built with which nitrogen source as well as the rates of production of different peptides. The switch to nitrate was accompanied by changes in protein synthesis and protein abundance in all three strains, and these metabolic changes were mostly unique to each strain. These results allow insights into how Synechococcus in the marine environment may be modifying their metabolisms to adjust to dynamic resource availability. The differences between strains highlight tradeoffs in resource allocation used to adapt to dynamic environments.

Primary Presenter: Angela Boysen, Pacific Lutheran University (aboysen@plu.edu)

Authors:

Jacob Waldbauer, University of Chicago  (jwal@uchicago.edu)