SANTA CRUZ, CA--An unusual microorganism discovered in the open ocean may force scientists to rethink their understanding of how carbon and nitrogen cycle through ocean ecosystems. A research team led by Jonathan Zehr, professor of ocean sciences at the University of California, Santa Cruz, characterized the new microbe by analyzing its genetic material, even though researchers have not been able to grow it in the laboratory.
Zehr said the newly described organism seems to be an atypical member of the cyanobacteria, a group of photosynthetic bacteria formerly known as blue-green algae. Unlike all other known free-living cyanobacteria, this one lacks some of the genes needed to carry out photosynthesis, the process by which plants use light energy to make sugars out of carbon dioxide and water. The mysterious microbe can do something very important, though: It provides natural fertilizer to the oceans by "fixing" nitrogen from the atmosphere into a form useable by other organisms.
"For it to have such an unusual metabolism is very exciting," Zehr said. "We're trying to understand how something like this can live and grow with so many missing parts."
A paper describing the new findings appears in the November 14 issue of the journal Science.
Earlier research by Zehr's group had revealed surprisingly large numbers of novel nitrogen-fixing cyanobacteria, including the one that is the focus of this study, in the open ocean. Although 80 percent of Earth's atmosphere is nitrogen, most organisms cannot use it unless it is "fixed" to other elements to make molecules like ammonia and nitrate. Because nitrogen is essential for all forms of life, nitrogen fixation is a major factor controlling overall biological productivity in the oceans.
The new microbe is one of the most abundant nitrogen fixers in many parts of the ocean, Zehr said. New DNA sequencing technology provided by 454 Life Sciences, a Roche company, enab
|Contact: Tim Stephens|
University of California - Santa Cruz