Those tiny bubbles.....(in YPD plates)

Mark Walberg walberg at
Thu Jan 18 14:15:37 EST 1996

Michael Lichten wrote:
> I'm a bit embarassed to post this, as one would think I would have solved
> this one by now....
> Recent batches of my YPD plates have many tiny bubbles in them, or what
> looks like tiny bubbles in the tetrad dissecting scope.  These bubbles are
> just a little bit smaller than a spore, so you can well imagine how much
> fun dissecting tetrads is on these plates.  To make matters worse, I KNOW
> that I solved this problem 10 years ago, but I can't for the life of me
> remember what the solution was.
> If anyone out there has observed this problem and solved it, PLEASE let me
> know ASAP.  In addition to driving me nuts, it's preventing me from
> introducing a new postdoc to the joys and pleasures of tetrad dissection.
> How can you tell someone that the way to tell the difference between a
> spore and a bubble is that a spore looks sporish?
> If anyone else has this problem and hasn't solved it, give me a call and
> we can have a good cry together....
> Michael Lichten
> lichten at
> --
> Michael Lichten
> lichten at

Two things can help.  
One is to run your gas burner while pouring plates, and 
flame briefly the agar surface (trying not to set the 
dish on fire).  
Another is to drop about 1 ml of ethanol into your media 
just before pouring to reduce surface tension and break 
the bubbles.  The ethanol isn't likely to affact the 
growth of most yeast. (Remember, they make ethanol.)

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