I have a problem which looks like a contaminating organism growing on
top of my yeast colonies. These are white, hard "spots" which only
appear after plates have been at 4deg for a while and on yeast growing on
ethanol or glycerol/ethanol plates. These "spots" have to be crushed
to view under the microscope but look like crushed glass in what could be
a lipid matrix. Gram stains do not show anything which looks like
another organism apart from yeast. The general opinion in my lab is that
the yeast is producing a lipid or polysaccharide but I would like to be
sure that there is no contaminant present before I start molecular work.
Has anyone experienced this kind of thing? Do yeasts have parasites such
as viruses? I would be grateful for advice and ideas on what is going on.