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Big, Beneficial Bacteria Discovered

By Jill Lee
December 30, 1997

Now, from a Raleigh sewer plant and the salt marshes of North Carolina, come newly discovered bacteria that break all the rules--and offer new possibilities for bio-fuels and environmentally sound farming.

All living things need nitrogen. Plants rely on soil bacteria to “fix” the nitrogen in the air and soil into a form the plants can use. Most bacteria use the soil nutrient molybdenum to do this. Until 1980, science said molybdenum was essential for nitrogen fixation. But in many southeastern soils, molybdenum is bound in a biologically unavailable form.

Scientist Paul Bishop of USDA’s Agricultural Research Service was the first to suggest bacteria might exist that didn’t require molybdenum to fix nitrogen. He proved this to skeptical colleagues in the United States and Europe by demonstrating that a particular bacterium, Azobacter vinelandii, can fix nitrogen without molybdenum.

Bishop’s research team has now found three new distinct bacteria that fix nitrogen in a molybdenum-free environment. Chemical analysis of these microbes shows they are unlike any other previously recorded. Researchers are working to give them a genus and species designation.

The bacteria might someday be used to boost nitrogen levels and improve crop fertility in molybdenum-poor fields. But these bacteria can do more than fix nitrogen where molybdenum is in short supply. They also release hydrogen that could be collected and harnessed as biofuel. Also, studying the biochemical mechanisms within the bacteria could lead to more economical and environmentally friendly ways to produce nitrogen fertilizer.

The bacteria are large--a specimen discovered at a Raleigh sewage plant is four to five times the size of typical soil bacteria. Researchers are calling it WWTP (for water waste treatment plant) until a scientific name is found. Another bacterial behemoth was coined SM(2) after its discovery in a salt marsh in Beaufort, N.C. The third one is called WB3 because it was found on Wrightsville Beach, N.C.

Scientific contact: Paul Bishop, ARS, Soybean and Nitrogen Fixation Laboratory, Raleigh, N.C., phone (919) 515-3770, fax 515-7867,