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Characteristic soil smell?

Moselio Schaechter mschaech at sunstroke.sdsu.edu
Wed Sep 27 14:59:56 EST 2000

At 8:05 AM -0700 9/26/00, Kate Orman wrote:
>I hope you'll forgive this intrusion - I'm a science fiction writer and a
>former microbiology student, racking my brains to remember something one
>of my lecturers once said! Apparently there's a particular soil microbe
>which gives soil its characteristic smell. I'd like to mention it in a
>story I'm writing, but I can't remember the organism's name for the life
>of me, and my research hasn't turned it up. I'd be most grateful for any
>Kate Blum Orman <korman at zip.com.au> http://www.zip.com.au/~korman/
>"I have no idea what that meant." - Dot Warner


The organisms associated with  garden soil smell are usually members of the
genus Streptomyces.  As a microbiologist past or present, you may know that
these are actinomycetes, a large group of the "higher" bacteria.  The
compounds usually blamed are called geosmins, which are unsaturated ring
compounds that belong to the sesquiterpenoids.  A common one  is trans-1,

You may remember that the actinomycetes are very prone to produce all sorts
of "secondary metabolites", including many major antibiotics.   As is usual
in the field of secondary metabolites, I doubt that anyone has any good
idea  why the organisms may want to produce an earthy smell.   Some
blue-green bacteria (cyanobacteria) also produce geosmins.

I can't quite picture how this will fit in a science fiction piece, but I
wish you success.  Let us know where this is going to appear.

Thanks for asking, even though this is outside the field of Mycology.

Elio Schaechter

Author, "In the Company of Mushrooms"
Harvard University Press

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