Growth at minus 70 C

Jim Mau elgusano at lapalapa.com
Fri May 30 11:19:23 EST 1997

John Cherwonogrodzky wrote:
> Dear Colleagues:
>      I have been doing a little work with mice infected with fungi. I have
> noticed that their serum samples, stored at minus 70 C have fungal growth at
> the top. I haven't had time to pursue this, but this observation runs counter
> to logic. Things don't grow on frozen media (though I once read that 15% of
> the water is still in liquid phase) I think It more likely that there was
> growth in the serum samples when I worked with these at room temperature, and
> then upon freezing the fungi were somehow compressed to the top by the
> formation of ice crystals. Any comment? Thanks...John

	What you are seeing may not be mycological growth but rather the
precipitation of fibrin from the serum sample.  This appears to be quite
common in samples stored at lower temps. (i.e. >-20 C).  As the moisture
in the sample evaporates (and yes samples do apparently 'dry out' even
in those nice cryo vials) the fibrin begins to ppt. & will eventually
dry out itself.  Hope this helps.


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