Deep-sea archaeon nitrogenase withstands 98 °C heat, study finds

September 19, 2026 at 04:56 PM1 min

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Researchers at the Max Planck Institute for Marine Microbiology isolated a nitrogenase enzyme from the deep-sea archaeon Methanocaldococcus infernus that remains stable up to 98 °C. The enzyme fixes nitrogen only at high temperatures, unlike most proteins that degrade in such heat. The findings suggest the enzyme may resemble an ancient common ancestor of nitrogenases.

Key Facts

The nitrogenase from Methanocaldococcus infernus began to break apart only at 90 °C and remained partially intact at 98 °C.
The enzyme produces ammonia only at high temperatures and is not active at room temperature.
The nitrogenase shares traits of molybdenum, vanadium, and iron forms, suggesting it may resemble a common nitrogenase ancestor.
Methanocaldococcus infernus lives in volcanic marine environments where vent fluids can exceed the boiling point of water.

Extreme Heat Stability

The isolated nitrogenase from Methanocaldococcus infernus remained stable at temperatures that destroy most proteins. The protein only began to break apart at 90 °C, and some of it remained intact even at 98 °C. First author Nevena Maslać compared the enzyme's stability to egg white cooked in hot water, noting that most proteins would rapidly decay under such conditions. The enzyme is not active at room temperature and produces ammonia only at high temperatures.

Evolutionary Significance

The nitrogenase from Methanocaldococcus infernus shares traits of the molybdenum, vanadium, and iron forms of the enzyme. Tristan Wagner, who leads the laboratory at the Max Planck Institute for Marine Microbiology, suggested this type of nitrogenase could be similar to a common nitrogenase ancestor. The enzyme's extreme stability allowed researchers to study nitrogenase states that are usually difficult to capture.