Plate Nº 97 · recorded October 9, 2026
Biology & EvolutionReported finding
Scientists map molecular 'off switch' for nitrogen fixation
A University of Arkansas team has mapped the protein complex that halts nitrogen fixation in a methane-producing microbe. The 2026 Nature study could one day help crops like corn produce their own fertilizer.
By Nathan Brooks3 min read554 words
In brief
- Paper published in Nature in 2026 with DOI 10.1038/s41586-026-11116-z
- Almost 80% of Earth's atmosphere is nitrogen gas, which most organisms cannot use directly
- Corresponding author Dan Lessner is a professor of biological sciences at the University of Arkansas; first author is Rajnandani Kashyap
- Researchers used cryo-electron microscopy to capture a supercomplex in which two regulatory proteins lock nitrogenase into an inactive state
- Industrial Haber-Bosch fertilizer supports roughly half of global food production, a process the team says nitrogenase could eventually replace in crops
A University of Arkansas-led team has mapped the protein complex that switches off nitrogen fixation in a methane-producing microbe—a study published in the journal Nature in 2026.
"This discovery reveals an entirely new strategy for regulating one of the most important biochemical reactions on Earth," said Dan Lessner, a professor of biological sciences at the University of Arkansas and the paper's corresponding author.
What did the team find?
Almost 80% of Earth's atmosphere is nitrogen gas, but most organisms cannot use it directly. Certain microbes instead rely on an enzyme called nitrogenase, which converts the gas into ammonia—a building block for proteins, DNA and fertilizers.
Working with a methanogen (a microbe that produces methane), the researchers used cryo-electron microscopy—a technique that freezes proteins and images them at near-atomic resolution—to watch how nitrogenase interacts with regulatory proteins known as PII proteins.
They found that two of those regulators grip the nitrogenase and lock it into a large, inactive assembly the authors call a protein supercomplex.
How does the switch work?
When the microbe runs low on energy or nutrients, the supercomplex stays assembled and halts nitrogenase. Once conditions improve, cellular signals trigger the supercomplex to fall apart, freeing the enzyme to resume making ammonia.
The paper's first author is Rajnandani Kashyap, with collaborators at institutions across the U.S. The work offers a first structural look at how methanogens, a poorly studied group, control a globally important process.
Why does nitrogen fixation matter?
Today, the Haber-Bosch process—the industrial method behind most modern fertilizer—burns fossil fuels at high pressure to convert atmospheric nitrogen into ammonia. That fertilizer feeds roughly half of the world's food supply, but runoff can trigger algal blooms, degrade habitat and lower biodiversity.
"The biggest limitation in the growth of plants is often having access to enough nitrogen, even when they have enough sunlight, water and CO2," Lessner explained. "If they don't have enough nitrogen, you're not going to grow very big plants, especially in terms of providing plant material for humans and animals."
Could crops one day make their own fertilizer?
Nitrogenase performs the same chemistry at standard temperature and pressure, without fossil-fuel inputs. Researchers have long hoped to transplant the enzyme into crops, so plants could pull nitrogen straight from the air.
Because the new work is genetically based, the team could eventually move the information they learned into crops such as corn, Lessner noted. Self-fertilizing plants would cut demand for synthetic fertilizer, easing the runoff problem.
The same regulatory machinery might also let bioengineers toggle nitrogenase activity on demand, fine-tuning ammonia production without modifying the enzyme itself.
What are the limits of the work?
The structure was captured in a single methanogen. No one has yet engineered a crop with a working nitrogenase pathway. Nitrogenase also breaks down in oxygen, so any future plant version will need new strategies to shield the enzyme inside plant cells.
The authors describe the finding as a structural and mechanistic advance, not a finished biotechnology product. Translating the result into field-ready plants will likely take years of additional research.
The paper, "Cryo-EM structure of a methanogen nitrogenase–PII protein supercomplex," appears in Nature. Its DOI is 10.1038/s41586-026-11116-z.
via Phys.org Biology (Source)
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