"That has multiple implications," Zehr said. "It must have a 'lifestyle' that's very different from other cyanobacteria. Ecologically, it's important to understand its role in the ecosystem and how it affects the balance of carbon and nitrogen in the ocean."
During photosynthesis, photosystem II generates oxygen by splitting water molecules. Because oxygen inhibits nitrogen fixation, most nitrogen-fixing cyanobacteria only fix nitrogen at night, or do it in specialized cells. The lack of photosystem II enables the new microbe to fix nitrogen during the day, Zehr said.
But without photosynthesis, it can't take carbon dioxide from the atmosphere and convert it into sugars. So it's not clear how the new microbe feeds itself. Either it has some way of feeding on organic matter in its environment, or it lives in close association with other organisms that provide it with food, Zehr said.
"It would make a perfect symbiont because it could feed nitrogen to its host and live on the carbon provided by the host," he said.
Zehr's team was able to obtain a mostly pure sample of these unique cyanobacteria using a flow cytometer--a device that rapidly sorts individual cells based on size and color. The flow cytometer can take the cell soup from an ocean sample, classify each cell as it passes through laser beams, and sort different cell types into separate containers. A cell type that makes up a small percentage of the original sample can be concentrated to nearly pure levels using flow cytometry.
The team harvested DNA from the concentrated sample of cyanobacteria and sequenced it using the Genome Sequencer FLX system from 454 Life Sciences. The company's new sequenc
|Contact: Tim Stephens|
University of California - Santa Cruz