Geosmin

Geosmin Structural Formulae

Geosmin is an organic compound with the formula C₁₂H₂₂O. It is a terpenoid and is produced by various microorganisms, including certain bacteria and fungi. Geosmin is responsible for the earthy taste and odor that occurs in some freshwater fish and the distinctive smell of soil after rain, often referred to as "petrichor." The human nose is extremely sensitive to geosmin, and it can be detected at very low concentrations.

Production and Occurrence

Geosmin is produced by Streptomyces, a genus of Actinobacteria, and by some species of cyanobacteria. These microorganisms release geosmin into the surrounding water or soil, contributing to the characteristic earthy smell. In aquatic environments, geosmin can lead to off-flavors in drinking water and in fish, which can be a problem for water suppliers and aquaculture operations.

Detection and Removal

Due to its impact on water quality and the aquaculture industry, the detection and removal of geosmin are important areas of research. Various methods, including activated carbon treatment, ozonation, and biological filtration, have been explored for reducing geosmin levels in water supplies.

Health Effects

Geosmin is not known to be harmful to humans in the concentrations typically encountered in the environment. However, its presence in drinking water and food products can lead to aesthetic issues, affecting the taste and smell, which may lead to consumer complaints.

Cultural and Scientific Interest

The ability of humans to detect geosmin at low concentrations is thought to be an evolutionary adaptation, possibly linked to the avoidance of spoiled water and food. The smell of rain, often associated with geosmin, has been a subject of poetic and scientific interest for centuries. Research into geosmin and related compounds also contributes to our understanding of human olfactory perception.