Researchers take a lesson from bacteria

team of researchers from the University may have found a way to revolutionize one of the world's largest chemical production businesses--extracting nitrogen from the air to produce fertilizer. And they made their discovery by studying some rather unassuming bacteria.

The current technique used by chemical companies to pull nitrogen from the air to produce fertilizer involves a complex process of heating dangerously combustible hydrogen under very high pressures. However, tiny bacteria in the ground also extract nitrogen from the air--but at room temperature and at everyday pressures.

"Nature figured out how to fix nitrogen a billion years before we did," says Patrick Holland, assistant professor of chemistry and author of the research published in the latest issue of the Journal of the American Chemical Society. "We're just playing catch-up."

Bacteria called azotrophs on the roots of plants take nitrogen from the air and "fix" it, turning it and hydrogen into ammonia that plants use to make DNA and proteins.

Since the early part of the twentieth century, when chemist Fritz Haber discovered that iron can be used on a large scale to fix nitrogen, iron has been recognized as playing an important role as a catalyst. Bacteria also use iron, but Holland has found that the way in which bacteria's iron is bonded may be the key to how nature can fix nitrogen without the pressures and temperatures the man-made process demands.

Holland's team used X-ray diffraction, in which a computer-controlled device bombards the compound with X-rays, to inspect its structure. "When we looked at the analysis, we saw a nitrogen molecule stuck to iron and being stretched apart," says Holland.

Since the iron atoms in his model were bonded in only three places instead of the more usual six, "three-coordinate iron seems to be especially good for holding nitrogen tightly."

Knowing how nature so easily pulls nitrogen from the atmosphere may lead to a better understanding of how the ecology may balance itself and may eventually provide a safer, more economical method of nitrogen fixing for the multi-billion-dollar fertilizer industry.

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