skorycd at ncaur1.ncaur.gov
Mon Sep 25 10:16:20 EST 1995
I have been trying to use 2-deoxy-galactose (DG) to isolate gal
mutants in the yeast Candida wickerhamii. Some interesting
things have occurred with just trying to inhibit the cells with
the DG. When using standard protocols of plating the yeast on
YNB (2 % glycerol, 0.5 % DG), we still get growth with multiple
phenotypes appearing. The majority of the colonies are small and
there are several different looking big colonies within the
small. This is definitely a pure culture taken from a single
colony. Replating any of the big colonies yields an identical
looking big colony (ie: plating 3-4 different looking big
colonies on the same plate results in plate of seemingly pure
culture of big colonies). Replating a single small colony
results in phenotype mix similar to the first plate.
Total inhibition of all cell growth was finally achieved by
substituting sucrose for the glycerol. However, the same mixed
phenotypic growth still occurred if the sucrose/DG mix was used
with complex medium (eg yeast extract, peptone).
Does anyone have any idea of what could be occurring here.
Could this be a petite effect or a ploidy effect? I am at a
loss as to what is happening. Any suggestions would be
Christopher D. Skory, Ph.D.
National Center for Agricultural
Utilization Research, USDA-ARS
Fermentation Biochemistry Unit
Peoria, Illinois 61571-3902
E-mail: skorycd at ncaur1.ncaur.gov
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