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Enzyme finding could help lead to better smelling wine and water

Everyone knows that pleasant "earthy" smell of newly ploughed soil and the unpleasant "musty" smell of water, fish, and corked wine. Now, scientists have discovered how geosmin, the chemical responsible for those smells, is formed. David Cane and two of his graduate students at Brown University in Providence recently demonstrated the mechanism by which geosmin is produced, by splitting the enzyme responsible for geosmin synthesis into two halves. They then demonstrated that the first half of the enzyme converts another organic compound called farnesyl diphosphate to an intermediate product and the second half converts this intermediate product to geosmin. This is a surprising finding because researchers so far believed that one half of the enzyme was inactive. Researchers also demonstrated that geosmin is not produced if one half of the enzyme is blocked, proving that both halves of the enzyme are actually active but work in two separate specialized ways to produce geosmin.

BOTTOM LINE: "We now know how this substance, that everyone on earth knows, is produced," said Cane. "Knowing how it is produced has economic implications because we can now devise ways to control the 'musty' smell of water, fish, wine or even the damp smell in moldy buildings."

CAUTIONS: This is the first study to uncover the basic mechanism of geosmin formation and more studies are necessary to understand it in more detail.

WHAT'S NEXT: Cane and colleagues want to find out how the two halves of the enzyme responsible for geosmin synthesis "talk" to each other - how the product produced by one half is sensed and taken up by the other half to complete the process.

WHERE TO FIND IT: Nature Chemical Biology online, Sept. 16



Technology allows scientists to watch animals
turn thin air into food
Using technology developed at Harvard Medical School, scientists are now able to see how clams make food out of thin air. The process, known as nitrogen fixation, is fundamental to the food chain, influencing everything from agriculture to fisheries. While plants are the primary nitrogen fixers, biologists have suspected that some animals can also transform nitrogen into protein through a symbiotic relationship with bacteria living inside their bodies. Daniel L.Distel and his colleagues at the Ocean Genome Legacy, a nonprofit research institute in Ipswich, studied nitrogen fixation in shipworms, long-necked mollusks that munch on wooden ships and piers. The wood lacks enough nutrients for shipworms to survive, so they get nutrients from nitrogen dissolved in the ocean instead, Distel said. The researchers exposed the creatures to a nitrogen-rich solution, then used a highly sensitive device known as a multi-isotope imaging mass spectrometer, or MIMS, to trace the path the nitrogen took as it was digested by bacteria living in cells in the clams' gills. "Where nitrogen fixers are and how they work is probably one of the biggest unanswered questions in biology," said Paul Falkowski, a professor at Rutgers University's Institute of Marine and Coastal Sciences, who was not involved in the study.

BOTTOM LINE: Scientists can now observe at the cellular level how animals are absorbing and benefiting from nitrogen, a key element for life on earth.

CAUTIONS: The researchers were unable to explain how the shipworms insulate the bacteria from oxygen, which is usually present in an animal's gills and can stall nitrogen fixation.

WHAT'S NEXT: Understanding how animals fix nitrogen might help agricultural engineers improve the process in plants, allowing farms to produce more food while conserving fertilizer, Distel said.

WHERE TO FIND IT: Science, Sept. 14


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