Nitrogen gas is abundant in Earth's atmosphere, but most living organisms can't readily use this nitrogen. Only a subset of microbes that have enzymes known as nitrogenases can break nitrogen gas apart and convert it into ammonia. There are three different classes of nitrogenases found in nitrogen-fixing microbes, which vary based on the types of metal that they contain. Nitrogenases that contain the metal molybdenum are the most efficient, and two new studies from MIT offer an explanation for why that is. The team found that while molybdenum doesn't directly bind to nitrogen, it helps nearby iron atoms bind to nitrogen more strongly. This is a critical first step in breaking the bond between the two nitrogen atoms that form nitrogen gas. 'It's that initial binding step that's really the hard part. Once you've started to break the nitrogen-nitrogen triple bond and make some new nitrogen-hydrogen bonds, it's pretty easy to get the rest of the way,' says Daniel Suess, the Arthur Amos...
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