Planet's nitrogen cycle overturned by 'tiny ammonia eater of...( It's not every day you find clues to...)

It's not every day you find clues to the planet's inner workings in aquarium scum. But that's what happened a few years ago when University of Washington researchers cultured a tiny organism from the bottom of a Seattle Aquarium tank and found it can digest ammonia, a key environmental function. New results show this minute organism and its brethren play a more central role in the planet's ecology than previously suspected.

The findings, published online today in the journal Nature, show that these microorganisms, members of ancient lineage called archaea, beat out all other marine life in the race for ammonia. Ecologists now assume that ammonia in the upper ocean will first be gobbled up by phytoplankton to make new cells, leaving very little ammonia for microbes to turn into nitrate.

"Our data suggests that it's the other way around," said co-author Willm Martens-Habbena, a UW postdoctoral researcher. "Archaea are capable of stealing the ammonia from other organisms and turning it into nitrate. Then it's the phytoplankton that take up that nitrate once again."

Ammonia is a waste product that can be toxic to animals. But plants, including phytoplankton, prize ammonia as the most energy-efficient way to build new cells.

The new paper also shows that archaea can scavenge nitrogen-containing ammonia in the most barren environments of the deep sea, solving a long-running mystery of how the microorganisms can survive in that environment. Archaea therefore not only play a role, but are central to the planetary nitrogen cycles on which all life depends.

"Bacterial nitrifiers were discovered in the late 19th century. One century later this other group of nitrifiers is discovered that is not a minor population, it turns out to be the major population," said co-author David Stahl, a UW professor with appointments in the departments of civil and environmental engineering and microbiology. "We have to revise our basic unde
'/>"/>