Saturday, October 09, 2004

Department of State Washington File: Text: Genome Shows How Ocean Algae Helps Absorb Carbon Dioxide

Department of State Washington File: Text: Genome Shows How Ocean Algae Helps Absorb Carbon Dioxide: "These organisms are incredibly important in the global carbon cycle,' says Virginia Armbrust, a University of Washington associate professor of oceanography and lead author of the Science paper. Together, the single-celled organisms generate as much as 40 percent of the 50 billion to 55 billion tons of organic carbon produced each year in the sea and in the process use carbon dioxide and produce oxygen. And they are an important food source for many other marine organisms.

Scientists would like to better understand how these organisms react to changes in sea temperatures, the amount of light penetrating the oceans, and nutrients. 'Oceanographers thought we understood how diatoms use nitrogen, but we discovered they have a urea cycle, something no one ever suspected,' Armbrust says. A urea cycle is a nitrogen waste pathway found in animals and has never before been seen in a photosynthetic eukaryote like a diatom, she says. Nitrogen is crucial for diatom growth and is often in short supply in seawater, depending on ocean conditions. The genome work revealed that the diatom Thalassiosira pseudonana has the genes to produce urea-cycle enzymes that may help to reduce its dependence on nitrogen from the surrounding waters.

The genome work also shed additional light on how this diatom species uses fats, or lipids, which it is known to store in huge amounts. 'Learning the actual pathways they use to metabolize their fats helps explain the ability of diatoms to withstand long periods with little sunlight--even to overwinter--and then start growing really rapidly once they return to sunlight,' she says.
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