Geosmin, the chemical responsible for earthy smell after rain.
Geosmin is an organic compound with a distinct earthy flavour and aroma produced by a type of Actinobacteria, and this is responsible for the earthy taste of beets and a contributor to the strong scent that occurs in the air when rain falls after a dry spell of weather or when the soil is disturbed.
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| Chemical structure of Geosmin |
In chemical terms, it is a bicyclic alcohol with formula C12H22O. Geosmin is produced by the gram-positive bacteria Streptomyces, a genus of Actinobacteria and released when the organism dies. In 2006, the biosynthesis of geosmin by a bifunctional Streptomyces coelicolor enzyme was unveiled. A single enzyme, geosmin synthase (SCO6073 gene product) converts Fernesyl diphosphate (FPP) to geosmin in a two-step reaction (FPP → Germacardienol → Geosmin)
