Nitrogenase is the enzyme that pulls nitrogen from the air and turns it into ammonia, the reaction behind all biological fertilizer. It is also expensive for a cell to run. Rajnandani Kashyap and Edwin Antony at Saint Louis University used cryo-electron microscopy to image a native nitrogenase from a methane-making microbe, Methanosarcina acetivorans. It is the first such structure from this group of organisms. They caught it locked in an off state, held shut by two regulatory proteins clamped onto either end. In other words, the microbe has a built-in switch to stop the enzyme when it is not needed. As someone who spent a PhD on nitrogen-fixing bacteria, I am glad to see the archaeal version get this kind of attention. The authors call it basic research, and they are right to. Engineering crops to fix their own nitrogen remains a distant goal, but you cannot rewire a machine you cannot see.
Source: Nature, 7 October 2026
