Investigating the Unique Ability of Trichodesmium to Fix Carbon and Nitrogen Simultaneously Using MiMoSA

Joseph Gardner, Bri-Mathias Hodge, Nanette Boyle

Research output: Contribution to journalArticlepeer-review

4 Scopus Citations

Abstract

The open ocean is an extremely competitive environment, partially due to the dearth of nutrients. Trichodesmium erythraeum, a marine diazotrophic cyanobacterium, is a keystone species in the ocean due to its ability to fix nitrogen and leak 30 to 50% into the surrounding environment, providing a valuable source of a necessary macronutrient to other species. While there are other diazotrophic cyanobacteria that play an important role in the marine nitrogen cycle, Trichodesmium is unique in its ability to fix both carbon and nitrogen simultaneously during the day without the use of specialized cells called heterocysts to protect nitrogenase from oxygen. Here, we use the advanced modeling framework called multiscale multiobjective systems analysis (MiMoSA) to investigate how Trichodesmium erythraeum can reduce dimolecular nitrogen to ammonium in the presence of oxygen. Our simulations indicate that nitrogenase inhibition is best modeled as Michealis-Menten competitive inhibition and that cells along the filament maintain microaerobia using high flux through Mehler reactions in order to protect nitrogenase from oxygen. We also examined the effect of location on metabolic flux and found that cells at the end of filaments operate in distinctly different metabolic modes than internal cells despite both operating in a photoautotrophic mode. These results give us important insight into how this species is able to operate photosynthesis and nitrogen fixation simultaneously, giving it a distinct advantage over other diazotrophic cyanobacteria because they can harvest light directly to fuel the energy demand of nitrogen fixation.

Original languageAmerican English
Number of pages14
JournalmSystems
Volume8
Issue number1
DOIs
StatePublished - Jan 2023

Bibliographical note

Publisher Copyright:
© 2023 American Society for Microbiology. All rights reserved.

NREL Publication Number

  • NREL/JA-6A40-85274

Other Report Number

  • Article No. e00601-20

Keywords

  • cyanobacteria
  • flux analysis
  • metabolic modeling
  • systems biology

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