> ==========
> bionet/microbiology #4314, from hvartan at greenneedles.ultranet.com,
1514 chars, Fri 15 Nov 1996 00:25:31
> ----------
> Article: 5315 of bionet.microbiology
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> From: hvartan at greenneedles.ultranet.com (Hugh Vartanian)
> Newsgroups: bionet.microbiology
> Subject: Source of bad smells: rotten eggs,skunk cabbage, etc.
> Date: Fri, 15 Nov 1996 00:25:31 GMT
> Organization: UltraNet Communications, Inc.
> Lines: 15
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> Summary: Looking for microbiological treatise on source of unpleasant
odors such as rotten eggs, skunk cabbage, sour milk, etc.
> Keywords: bacteria, bad smell
> X-Newsreader: Trumpet for Windows [Version 1.0 Rev B final beta #4]
>> Hi
> I'm writing a children's book on gross smells. One of the premises of
the
> book is to provide a scientific explanation of the sources of such
everyday
> unpleasant odors such as rotten eggs (I kind of doubt it is hydrogen
sulfide
> or that the yellow of egg yolks is from sulfur), skunk cabbage
(perhaps I
> should check the botanical sources?), sour milk, etc. I have a handle
on the
> basic function of the olfactory system, but am at a loss to find
> information on this stuff. Is it bacterial fecal matter that causes
the odors
> or what?
> Any thoughts would be greatly appreciated.
>> Thanks,
> Luann
>luann1212 at aol.comComments so far are on the ball.
Another thing to consider is that most of the evil smelling amines are
produced under anaerobic conditions. in other words, conditions of
decomposition that are rapid enough to use up available oxygen.This
means that they can be "buried" within a mass of decomposing material
and only released when it is stirred ! A stagnant pond is a good
example. "Bad eggs" (hydrogen sulphide) may often be produced by
organisms seeking an "alternative" to dissolved oxygen by "using" the
oxygen locked up in sulphate ions - hydrogen sulphide can result. Hence
the interest in "sulphate reducing bacteria (SRB's).
Other "gross" smells can be from even simpler compounds like butyric
acid (rancid butter smell). This can also be the reason why silage can
smell repulsive if things have gone rather wrong with the microbial
fermentation.
For the kids it might be useful to point out that evil smells are very
useful to carrion feeding flies as an indication of where there might be
a good meal. So keen are some flies on tracking down the source of the
bad smell that fungi such as Stinkhorns produce their own evil smell
deliberately to attract flies which then help in spreading the fungus
spores around.
All this reminds me of an old research colleague who used to say "It
might look like manure to you but it's my bread and butter".
Best wishes,
Peter Harris,
Reading, UK.
