Engineering Nitrogen Fixation Activity in an Oxygenic Phototroph
Deng Liu1, Michelle Liberton1, Jingjie Yu1
1Department of Biology, Washington University, St. Louis, Missouri, USA.
Mbio
|June 7, 2018
Summary
Researchers engineered nitrogen fixation in a non-fixing cyanobacterium by transferring nitrogen fixation (nif) genes. This breakthrough enhances oxygen tolerance and sets a foundation for nitrogen-fixing crop plants.
Area of Science:
- Synthetic biology
- Microbiology
- Biotechnology
Background:
- Biological nitrogen fixation is essential for life but energetically costly and oxygen-sensitive.
- Engineering nitrogen fixation in oxygenic photosynthetic organisms is challenging due to nitrogenase's oxygen sensitivity.
- Cyanobacteria offer a model system as some are oxygenic photosynthesizers and nitrogen fixers.
Purpose of the Study:
- To engineer nitrogen fixation (diazotrophy) in the nondiazotrophic cyanobacterium *Synechocystis* sp. PCC 6803.
- To identify the minimal nitrogen fixation (nif) gene cluster required for activity.
- To enhance nitrogenase oxygen tolerance and overall activity.
Main Methods:
- Transfer of 35 nitrogen fixation (nif) genes from *Cyanothece* sp. ATCC 51142 to *Synechocystis* sp. PCC 6803.
- Identification of the minimal nif gene cluster for activity.
- Increasing nif gene expression and introducing uptake hydrogenase genes to enhance oxygen tolerance.
Main Results:
- Successfully engineered nitrogen fixation activity in *Synechocystis* 6803.
- Identified a minimal nif gene cluster essential for this activity.
- Achieved over 30% of the nitrogen fixation activity of the donor strain, *Cyanothece* 51142.
- Enhanced nitrogenase oxygen tolerance using uptake hydrogenase genes.
Conclusions:
- Demonstrated a feasible method for engineering nitrogen fixation in a nondiazotrophic oxygenic phototroph.
- Established *Synechocystis* 6803 as a model chassis for studying diazotrophy requirements.
- This work provides a critical baseline for engineering nitrogen fixation in crop plants, offering a sustainable alternative to chemical fertilizers.
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