Mystery behind fragrance from moist soil

Published: Wednesday 31 October 2007

how does moist soil get the sweet smell? It's a protein called geosmin that contributes the rich aroma. Though geosmin was identified more than a century ago, researchers from Rhode Island have recently been able to discover it and identify its characteristics.

Led by David Cane, scientists from Brown University have found that the gene responsible for geosmin formation in Streptomyces coelicolor, a strain of plant-munching bacteria found in soil. Last year, the team had discovered that a single protein converts the farnesyl diphosphate to geosmin. During the study, researchers have found that this protein folds into two distinct but connected parts, similar to a dumbbell. Geosmin is created by this enzyme.

The discovery is economically significant for water purification companies and wine makers since geosmin causes unpleasant odour and taste in drinking water, wine and other food.Experts say that the detection and elimination of geosmin is relatively difficult because of its exceptionally small size--less than 10 parts per trillion. It is resistant to removal by conventional water treatment due to the small size.

Jiaoyang Jiang, one of the researchers says that experts may find a way to block it- avoiding the foul taste, by understanding how the substance is synthesized.

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