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a beast ate my yeast, help!

Klaus Lehnert k.lehnert at auckland.ac.nz
Wed Aug 9 19:43:22 EST 2000

When that happens to me (not that I would admit it), I do exactly as Michael
says in (1), but first of all, I give the plate a good "wipe" with a yellow
bunsen flame. Idea is to kill as much of the fungus as possible before
picking the mess. Greatly increases your YRG2:beast ration. And the yeast is
somewhat protected from the flame by the fungus on top of it.

Have success!


"Michael Andres McMurray" <mmcmurra at u.washington.edu> wrote in message
news:Pine.A41.4.21.0008041130220.55688-100000 at dante01.u.washington.edu...
> 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!
> Michael
> 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?
> >
> > Thanks!
> >
> > Dan Riggs
> >
> ---

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