New findings suggest that the deep ocean is teeming with organisms that produce essential natural fertilizers. A National Science Foundation (NSF)-funded research team led by Jonathan Zehr, a marine scientist at the University of California, Santa Cruz, has discovered a previously unknown type of photosynthetic bacteria that fixes nitrogen, converting nitrogen from the atmosphere into a form other organisms can use. The researchers reported their findings in the August 9 issue of the journal Nature. Zehr has also found evidence that many additional kinds of nitrogen-fixing bacteria live in the open ocean.
"This discovery points to how little we know about the organisms that drive ocean biogeochemical processes," says Phil Taylor, director of NSF's biological oceanography program. "It may have profound influences on our thinking about and modeling of the global ocean nitrogen and carbon cycles."
Although nitrogen accounts for nearly 80 percent of the Earth's atmosphere, most organisms can use it only when it is "fixed" to other elements, to make compounds such as ammonia or nitrate. As a component of proteins, nitrogen is essential to all known forms of life.
Zehr and his coworkers found the nitrogen-fixing bacteria, which they have grown in the laboratory, in water samples collected from the Pacific Ocean near Hawaii. The organisms appear to belong to the genus
Synechocystis, a group of cyanobacteria (photosynthetic bacteria formerly known as blue-green algae) that includes both marine and freshwater species. The newly discovered nitrogen-fixers appear to be
active at greater depths and over longer time periods than other marine cyanobacteria known to fix nitrogen in the open ocean.
On land, nitrogen-fixing bacteria are a known quantity, residing in the roots of legumes like peas and beans. While many nitrogen-fixing cyanobacteria have been found in coastal waters, very few are known to occur in the open ocean.
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Contact: Cheryl Dybas
National Science Foundation
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