Don Nelson denelson at
Fri Feb 20 17:38:20 EST 1998

In article <199802191848.NAA08315 at>,
jprei001 at wrote:

> Dear Netters,
> a colleague of mine mentioned that he had problems with Kanamycin
> selection on medium containing Sigma Phytagel (selection was not
> effective, meaning everything grew, and no, he did not forget to put Km
> in the medium). Any of you has similar experience?
> Thanks,
> Hanna Preiszner

I have noticed a precipitate (or at least a cloud????) forming when adding
the antibiotic. Likely, it is related to the fact that the sulfate salt of
kanamycin is being used (usually kanamycin monosulfate is used) which
somehow reacts with the gellan gum (Phytagel). If this is happening in
your colleague's case, it would explain the result.


1) Add antibiotic dropwise when the temperature is high 80-90 degrees
(soon after out of the autoclave) with swirling.

2) Use agar.

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