Why does the rain smell so good?

It is nothing new. Perhaps you already know that when it rains the first drops that fall on dry soil favor the volatilization of geosmin, a compound produced by bacteria of the genus Streptomyces that live in the soil, creating a scent that has the evocative name of petricor or « wet earth ». But, have you wondered why the petricor smells good? Why is it pleasant to smell a molecule produced by soil microorganisms?

Research published in Nature Microbiology this week has been able, in part, to answer that question. After setting up small traps in the field and doing experiments in the lab, they have found geosmin to be attractive to springtails, tiny jumping arthropods abundant on the ground. And they might not be the only arthropods attracted to this scent.

Attracted like springtails to the petricor
Thanks to experiments, scientists discovered that springtails are great admirers of geosmin; that they can perceive it with their antennas and that they go to their origin for a very specific reason: to feed on the bacteria that release this smell.

But the authors have found out something else: The bacterium probably also capitalizes on this irresistible attraction. “(When a springtail) feeds on Streptomyces colonies, it spreads its spores through the faeces and by adhesion to its cuticle (the surface of its body),” the authors explain. Therefore, it could be said that all this is like a version of the attraction of bees for the aroma of flowers but in a miniature version.

“The results indicate that the production of geosmin (…) is an integral part of the sporulation process, essential to complete the life cycle of Streptomyces by facilitating the dispersal of its spores by means of arthropods,” the researchers concluded. . The next time you smell wet rain, you may remember that you are not the only one who finds it pleasant. .

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