Geosmin

Geosmin is a volatile organic compound produced by certain bacteria and fungi. Its distinctive earthy odor is especially noticeable after rain.

Streptomyces: A genus of soil-dwelling bacteria known for producing many antibiotics and other specialized metabolites. Many geosmin-producing soil bacteria belong to this genus.
Actinomycetes: A broad group of bacteria that includes many filamentous soil organisms. Geosmin production is widespread among actinomycetes, especially Streptomyces.
Taste and odor in drinking water: Unwanted flavors or smells in treated water, often caused by trace microbial compounds. Geosmin can make drinking water smell earthy even at very low concentrations.
2-Methylisoborneol: A microbial compound with a musty, earthy odor that can contaminate water and food. It often occurs alongside geosmin but has a distinct chemical structure and odor profile.
Geosmin synthase: A bacterial enzyme that converts farnesyl diphosphate into geosmin through a two-stage reaction. This enzyme directly catalyzes geosmin production in Streptomyces.
Myxobacteria: A group of soil bacteria that move in swarms and can form multicellular fruiting structures. Some myxobacteria produce geosmin independently of Streptomyces.
Water treatment: Processes that remove contaminants and make water suitable for its intended use. Treatment plants use adsorption and oxidation methods to reduce geosmin.
Ozone: A reactive form of oxygen whose sharp odor is associated with thunderstorms and electrical discharges. Ozone can accompany storm smells, but its sharp scent differs from geosmin's earthy odor.
Farnesyl diphosphate: A 15-carbon molecule used by organisms to build terpenes and other isoprenoids. Geosmin synthase uses this molecule as its starting material.
Cyanobacteria: A group of photosynthetic bacteria found in freshwater, marine, and terrestrial environments. Certain cyanobacteria produce geosmin, contributing to earthy tastes and odors in water.

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BeetrootRelated: Geosmin contributes to the earthy aroma and flavor associated with beetroot.