March 23, 2020
I can trap disease-carrying mosquitoes.
What molecule am I?
Image of Geosmin 3D Image of Geosmin

Geosmin is a natural bicyclic terpene with an earthy odor. According to The Merck Index, it is the “major volatile component of beet essence, also . . . the potent earthy odor contaminant of fish, beans, [and] water.” The human nose can detect it at concentrations in air as low as 5 ppt.

In 1936, A. C. Thaysen at the Chemical Research Laboratory, Teddington (London) described an odorous compound produced by actinobacteria in fishing streams. About 30 years later, Nancy N. Gerber and Hubert A. Lechevalier at Rutgers University (New Brunswick, NJ) isolated it from several Streptomyces spp. They did not determine its structure but named it geosmin from the Greek words for “earth” and “smell”. Biochemist Gerber later elucidated its structure.

Flash forward to 2019, when biologist Marcus C. Stensmyr and postdoc Nadia Melo at Lund University (Sweden) observed that yellowfever mosquitoes (Aedes aegypti) are attracted to geosmin. Their colleagues at Florida International University (University Park) showed that A. aegypti like the odor so much that they lay their eggs in geosmin baits.

Beet peels are rich in geosmin, so Stensmyr engaged a team at the Federal University of Alagoas (Maceió, Brazil) to construct and test a simple trap baited with beet-peel extract. This is a win–win situation because the peel is a waste product. Stensmyr’s next steps are to optimize the trap and observe whether it significantly decreases mosquito populations. 

Geosmin hazard information

Hazard class*Hazard statement
Serious eye damage/eye irritation, category 2AH319—Causes serious eye damageChemical Safety Warning

*Globally Harmonized System of Classification and Labeling of Chemicals.
Explanation of pictograms.

Geosmin fast facts

CAS Reg. No.19700-21-1
4a(2H)-Naphthalenol, octahydro-4,8a-dimethyl-, (4S,4aS,8aR)-
Empirical formulaC12H22O
Molar mass182.30 g/mol
AppearanceColorless solid or oil
Melting point47 ºC
Boiling point270–271 ºC
Water solubility160 mg/L (est.)

MOTW update: 
April 27, 2020

Geosmin is a natural bacterial product that is found in beet peels, among other plant parts. Yellowfever mosquitoes are attracted to beets, so scientists are experimenting with traps baited with the peels. Geosmin is made by Streptomyces bacteria in beets. Swedish scientists have discovered that tiny invertebrates called springtails are also attracted to the geosmin in beets. They help the bacteria reproduce by spreading their spores into the environment.

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