Investigating the Unique Ability of Trichodesmium To Fix Carbon and Nitrogen Simultaneously Using MiMoSA
Joseph J Gardner1, Bri-Mathias S Hodge1,2,3, Nanette R Boyle1,4
1Chemical and Biological Engineering, Colorado School of Mines, Golden, Colorado, USA.
Msystems
|January 4, 2023
Summary
Trichodesmium erythraeum fixes nitrogen and carbon simultaneously, a unique trait among cyanobacteria. Advanced modeling reveals cells maintain microaerobic conditions using Mehler reactions to protect nitrogenase from oxygen.
Area of Science:
- Marine microbiology
- Biogeochemical cycles
- Metabolic modeling
Background:
- Trichodesmium erythraeum is a key marine cyanobacterium vital for the global nitrogen cycle.
- It uniquely fixes nitrogen and carbon simultaneously without specialized heterocysts.
- Understanding this mechanism is crucial for marine ecosystem dynamics.
Purpose of the Study:
- To investigate the mechanisms Trichodesmium erythraeum uses for simultaneous carbon and nitrogen fixation.
- To model how this cyanobacterium protects nitrogenase from oxygen poisoning.
- To elucidate the metabolic strategies enabling its ecological success.
Main Methods:
- Utilized the multiscale multiobjective systems analysis (MiMoSA) modeling framework.
- Simulated nitrogenase inhibition kinetics using Michealis-Menten competitive inhibition.
- Analyzed metabolic flux differences between filament cells.
Main Results:
- Nitrogenase inhibition is best described by Michealis-Menten competitive inhibition.
- Cells maintain microaerobic conditions via high flux through Mehler reactions.
- Cells at filament ends exhibit distinct metabolic modes compared to internal cells.
Conclusions:
- Trichodesmium erythraeum employs microaerobic strategies to protect nitrogenase during simultaneous photosynthesis and nitrogen fixation.
- Mehler reactions play a critical role in reducing intracellular oxygen.
- Location-specific metabolic adaptations contribute to the organism's efficiency.
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