I would think the easiest way to separate the contaminating fungus from
the desired one would be either to (1) take a glob of cells from the
master plate that contains as many Saccharomyces cells per fungal mess as
possible, resuspend it in some sterile water, dilute it and plate for less
than 20 single colonies per plate. If you can get the single cells spread
out far enough and if the ratio of contaminant to YRG2 is low enough (and
you could use less or more than 20 to deal with this), you
should be able to get individual YRG2 colonies free of contamination --
just streak them to a new plate as soon as you can tell what kind of
colony they are!
Alternatively, (2) you could take a glob as in (1) and streak it for
single colonies on a new plate, but before you let it grow
use a micromanipulator and a dissection microscope to physically pull off
single Saccharomyces cells and transfer them to a new plate, one by one to
get a few different colonies. Then streak for singles again to make sure
the resulting colonies are pure.
Hope this helps!
On 1 Aug 2000, Dan Riggs wrote:
> We have been conducting a protracted 2 hybrid screen and finally got a
> positive signal by x-gal selection. Unfortunately, the master plate is
> contaminated by a fungus which grows much faster than does yeast (on
> triple drop out medium). The yeast strain we are using is YRG2 from
> Stratagene, and its genotype doesn't suggest to me that one could expect
> to plate it on some selection medium to rid the cells of the
> contaminant. Does anyone have any advice?
>> Dan Riggs