Yeast Infestation

Emma Rushton rushton at biology.utah.edu
Wed Sep 17 16:00:31 EST 1997


In article <Pine.OSF.3.96.970909163326.32546A-100000 at ucs.orst.edu>,
emeryh at UCS.ORST.EDU (Henry Emery) wrote:
> if I could get any insight if anyone knows of a way to get rid of the
> yeast. I was trying to find out about antifungal treatments that we could
> put in the fly diet, so that the adult flies could injest it and kill the
> yeast. Does anyone know of such a treatment that would not harm the flies?

Most labs use anti fungal agents in their fly food.  Ashburner (Drosophila,
a Laboratory Handbook, 38/7 p1201) suggests methyl p-hydroxybenzoate aka
Nipagin M aka Tegosept at a final conc of 0.07%.  You make it up as a 10%
solution in ethanol and add it to the food as it cools.  We found this to
work well in my old lab, except on one stubborn yeast infection which
appears to grow anaerobically between the food and the vial wall.  For this
we used propionic acid as well as the nipagin.  We always used both
chemicals as a default. 

Ashburner (same ref) says that the amount of propionic acid added depends
on the pH of the food.  The amount of undissociated acid should be at least
0.012M, up to 0.04M.  At pH 5, the optimal amount is 2.1 ml/L, at pH 6 it
is 12.2 ml/L.

Ashburner also discusses other anti-fungal agents and techniques, but the
two described above are the only ones I know about first hand.

Good luck, Emma



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