yeast and minimal media plates

Adrienne Horowitz aahorowitz at
Wed Jan 31 18:17:28 EST 1996

debbritt at (Deb Britt) wrote:
> We are starting some work with the Clontech Matchmaker system.  I plated
> the Y190 host strain on YPD, then used that to inoculate some minimal media
> plates, specifically SD lacking leucine, tryptophan, or both.  The strain
> shouldn't grow, but I saw growth on all plates, though admittedly not a
> lot.  I know that with bacteria you often need to make minimal plates using
> noble agar, because the (bacto) agar may have traces of amino acids.  Is
> this the case for yeast as well?  Should I be using purified agar?  I would
> appreciate any comments from people who use minimal media for selection
> protocols.  Thanks in advance!
> -- 
> Deborah Britt, Ph.D.
> Medical Oncology
> RI Hospital/Brown University


The plates we use for two-hybrid screening at CLONTECH are made from 
(bacto) agar.  The yeast should not require a minimal media agar.   
Y190's are not leaky for either leu or tryp, so you should not see 
growth of untransformed Y190's on double or single dropout media.  
Plausible explanations for the "colonies" you are seeing could be one 
of the following: 1. If you are growing the yeast at very high plating 
densities, you may see a haze of dead cells, but no true colonies
should form.  2.The growth you see may have resulted from airborne  
fungal or bacterial contamination.
(=)  Adrienne Horowitz
 X   Technical Service Specialist
(=)  CLONTECH Laboratories, Inc.
 X   ph: 800-662-2566 x 1434 
(=)  fx: 415-424-1064
 X   tech at
(=)  aahorowitz at

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