What is mildew odour made of?
August 2, 2024 6:17 AM Subscribe
So what makes mold/mildew smell the way it does? Why is it so detectable in such small amounts? I'd like scientific references.
Mold and mildew signal decay. It's seems likely that we would evolve to be particularly sensitive to those smells. The mutations that create evolution are random, but only useful mutations tend to stay.
posted by theora55 at 9:37 AM on August 2, 2024 [1 favorite]
posted by theora55 at 9:37 AM on August 2, 2024 [1 favorite]
In addition to scholarly stuff, which is often behind paywalls, Nose Dive by Harold McGee, is a great reference for this kind of thing. There's about four pages just on the topic of musty-earthy smells in the book.
The primary constituents of "musty" or "mildewy" smells include geosmin, 2-methylisoborneol (2-MIB), 2-isobutyl-3-methoxy pyrazine, 2-isopropyl-3-methoxy pyrazine and 2,4,6-trichloroanisole [1]. Most of these are produced by bacteria or blue-green algae, which are very ancient species. The evolutionary history of geosmin production has been studied some depth [2][3] but is complex, with no obvious single ancestor; however, the genes associated with geosmin appear to be highly conserved, suggesting that it has a powerful adaptive function.
All of these compounds can be detected at extremely low levels of concentration by many vertebrate and invertebrate species, suggesting a strong evolutionary benefit. A recent study [4] found that nematodes appear to be able to detect and avoid geosmin- and 2-MIB- producing bacteria, suggesting that this behavior is very ancient indeed. In the words of that paper:
[2] The diversity, origin, and evolutionary analysis of geosmin synthase gene in cyanobacteria
[3] A novel cyanobacterial geosmin producer, revising GeoA distribution and dispersion patterns in Bacteria
[4] The Unusual Functions of Geosmin
posted by graphweaver at 10:49 AM on August 2, 2024 [15 favorites]
The primary constituents of "musty" or "mildewy" smells include geosmin, 2-methylisoborneol (2-MIB), 2-isobutyl-3-methoxy pyrazine, 2-isopropyl-3-methoxy pyrazine and 2,4,6-trichloroanisole [1]. Most of these are produced by bacteria or blue-green algae, which are very ancient species. The evolutionary history of geosmin production has been studied some depth [2][3] but is complex, with no obvious single ancestor; however, the genes associated with geosmin appear to be highly conserved, suggesting that it has a powerful adaptive function.
All of these compounds can be detected at extremely low levels of concentration by many vertebrate and invertebrate species, suggesting a strong evolutionary benefit. A recent study [4] found that nematodes appear to be able to detect and avoid geosmin- and 2-MIB- producing bacteria, suggesting that this behavior is very ancient indeed. In the words of that paper:
"Geosmin thus acts as an aposematic signal, honestly and reliably advertising the unpalatability of its producers and providing a mutual benefit to predator and prey.”[1] Physical Chemical Characterization of Five Earthy-Musty-Smelling Compounds
[2] The diversity, origin, and evolutionary analysis of geosmin synthase gene in cyanobacteria
[3] A novel cyanobacterial geosmin producer, revising GeoA distribution and dispersion patterns in Bacteria
[4] The Unusual Functions of Geosmin
posted by graphweaver at 10:49 AM on August 2, 2024 [15 favorites]
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posted by pipeski at 7:05 AM on August 2, 2024 [1 favorite]