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| Vol. 17, No. 12 | Nov. 20, 1997 |
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| Vol. 17, No. 12 | Nov. 20, 1997 |
Burning coal, oil and gasoline releases carbon dioxide as well as nitrogen dioxide into the atmosphere, where these industrial gases trap heat near the Earth's surface. To understand this "greenhouse effect" and predict global warming, researchers must learn how carbon and nitrogen molecules cycle through the ocean-and that's easier said than done, according to David Kirchman, marine studies.
Kirchman has proposed an innovative way to investigate the breakdown of carbon in coastal waters by studying the degradation of chitin (pronounced KITE-un), a highly abundant, cellulose-like material generated by zooplankton, diatoms and other marine organisms.
Last month, the U.S. Department of Energy (DOE) applauded Kirchman's proposal, awarding him $366,000 to pursue it, in collaboration with researcher David Royer of Lincoln University. The three-year grant was one of only 20 distributed by the DOE.
"By tracking the fate of carbon and nitrogen in the ocean and studying its microbes, in some cases down to the molecular level, we hope to better understand the role of biology in global climate," explained Martha A. Krebs, director of the DOE's Office of Energy Research.
The UD project ultimately may help improve the accuracy of global-warming models, Kirchman said. It also should bolster Lincoln University's emerging ecological and environmental programs, while providing new research opportunities for UD students at the undergraduate and graduate levels, he added.
Lincoln, the oldest of the nation's historically black colleges and universities, has a reputation for excellence in the sciences. Now, the university is establishing a new program focusing on the environmental sciences, a field in which African Americans have traditionally been under-represented.
As director of UD's marine biology-biochemistry program within the highly rated College of Marine Studies, Kirchman had received previous DOE awards to study carbon cycling in coastal waters.
"Royer heard about this new grant opportunity, which requires the involvement of populations under-represented in marine sciences, and he called me up," Kirchman said. "I was delighted, because the participation of Lincoln students and faculty will enrich the learning experience for UD students."
The UD and Lincoln researchers will take a closer look at long-chain molecules generated by various marine organisms such as Thalassiorsira and Skeletonema, two types of diatoms that crank out chitin strands to make themselves more buoyant. Diatoms are "major players in spring algae blooms," Kirchman noted.
How could chitin help reveal carbon's fate in the environment? When large quantities of chitin are present in coastal waters, Kirchman explained, certain marine bacteria kick into overdrive, producing more chitin-degrading enzymes, known as chitinases. To extract nutrients from chitin, these bacteria must rely on chitinases to "hydrolyze" or fragment large organic molecules into carbon and other component compounds, which are small enough to cross cell membranes.
Smaller chitin fragments can then be "mineralized," or transformed into carbon dioxide, Kirchman said. In this way, chitinases may prevent some carbon-containing chitin from sinking into deep sea sediments. "Carbon buried deep beneath the oceans may remain safely encapsulated for hundreds of years, and therefore doesn't contribute to global warming," he noted. "Information about these chitin-degrading enzymes may help us understand organic matter degradation in the ocean, which would be useful for predicting atmospheric carbon levels," he said.
Kirchman will investigate chitinases in the lab by measuring the genetic expression of the enzymes within a slow-growing marine bacterium. Enzyme synthesis should speed up or slow down to keep pace with bacterial growth rates, he said. Kirchman also plans to trigger a golden-brown algae bloom in the lab, by adding excess nutrients to water. Chock-full of chitin, the bloom should boost the abundance and expression of chitinase genes- and perhaps suggest how many sinking carbon-based particles are present within a given marine environment.
Kirchman's research will address fundamental questions about the relationship between chitin and atmospheric carbon. In the future, he said, the work also may suggest a way to develop better forms of cellulose, a material that's structurally similar to chitin and essential to the paper and textile industries. Marine chitinases also might someday prove useful for fighting agricultural pests, since chitin is present in many crop-destroying insects and fungal pathogens. "It's possible," Kirchman said, "that these land-based pathogens and pests would be defenseless against a chitinase from a marine microbe."
-Ginger Pinholster
