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Feb 19, 2009
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Billions of years ago, microbes were key in developing modern nitrogen cycle

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[Source: ScienceDaily] - As the world marks the 200th anniversary of Charles Darwin's birth, there is much focus on evolution in animals and plants. But new research shows that for the countless billions of tiniest creatures – microbes – large-scale evolution was completed 2.5 billion years ago.

"For microbes, it appears that almost all of their major evolution took place before we have any record of them, way back in the dark mists of prehistory," said Roger Buick, a University of Washington paleontologist and astrobiologist.

All living organisms need nitrogen, a basic component of amino acids and proteins. But for atmospheric nitrogen to be usable, it must be "fixed," or converted to a biologically useful form. Some microbes turn atmospheric nitrogen into ammonia, a form in which the nitrogen can be easily absorbed by other organisms.

But the new research shows that about 2.5 billion years ago some microbes evolved that could carry the process a step further, adding oxygen to the ammonia to produce nitrate, which also can be used by organisms. That was the beginning of what today is known as the aerobic nitrogen cycle.

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