PNNL

Abstract

Diatoms dominate phytoplankton communities by outcompeting other taxa for nitrogen, yet little is known about the molecular underpinnings of this ability. As a consequence of their evolutionary history, diatoms possess traits that are both autotroph- and heterotroph-like expanding their metabolic capabilities beyond other model organisms. Here we use the model marine diatom Phaeodactylum tricornutum to investigate the extent to which diatoms have combined elements of nitrogen metabolism from each ancestral partner. Using a range of experimental and metabolic modeling approaches, we found compartment-specific assimilation of different forms of nitrogen, requiring the operation of metabolite shuttles to synchronize organellar metabolism. Further we identified a hybrid arginine biosynthesis pathway, clarifying the role of the urea cycle in diatoms. We conclude that metabolic integration between the major energy organelles, established post-endosymbiosis in diatoms, confers an advantage for nitrogen utilization of and contributes to their ecological success in a highly dynamic marine environment.