Down to earth chemistry

Geosmin is the smell of freshly turned earth. It is a bicyclic alcohol but until David Cane and his colleagues at Brown University figured it out, no one knew how nature makes this earthy molecule. "One nice thing about geosmin is that essentially everyone has smelled it, even if they did not know what it was or where it comes from," says Cane. He and graduate students Jiaoyang Jiang and Xiaofei have now used gas chromatography-mass spectrometry to track the biosynthesis of geosmin by a bifunctional enzyme from the soil microbe Streptomyces coelicolor. Until now, such a two-part enzymatic process was not known in the biosynthesis of this type of terpene.