Photosynthesizing bacteria with a day-night cycle contain rare ...( RICHLAND Wash. -- Researchers sequen...)

RICHLAND, Wash. -- Researchers sequencing the DNA of blue-green algae found a linear chromosome harboring genes important for producing biofuels. Simultaneously analyzing the complement of proteins revealed more genes on the linear and the typical circular chromosomes then they'd have found with DNA sequencing alone.

The team reported the cyanobacterium Cyanothece 51142's genome the week of September 15 in the Proceedings of the National Academy of Sciences Early Edition. Overlaying protein data let the researchers pinpoint about 16 percent more genes than by DNA sequencing alone. The collaboration included a proteomics team from the Department of Energy's Pacific Northwest National Laboratory, a gene sequencing team from the Washington University Genome Sequencing Center, and researchers from Washington University, Saint Louis University, and Purdue University.

"This is the first time anything like this has been found in photosynthetic bacteria. It's extremely rare for bacteria to have a linear chromosome," said team leader Himadri Pakrasi from WUSTL. "Nearly 100 percent of them do not."

Cyanobacteria are unique among bacteria because they seem part plant-like and part microbe-like. They use the sun's energy to make sugar via photosynthesis like plants do. And like bacteria, Cyanothece 51142 has other key life-sustaining functions, such as doctoring atmospheric nitrogen so other species can use it. This so-called nitrogen fixation is performed by a handful of bacterial species in water and soil. Cyanothece also makes ethanol and hydrogen, activities that drew the attention of the DOE and others looking for new ways to make fuel.

But unlike most bacteria, Cyanothece has a day-night schedule for performing work. It makes sugar in the daylight, but then spends its nights breaking down that sugar to fix nitrogen and to produce different compounds. And bacteria generally store their DNA in circu
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