drosophila cultures dying

Hello. My daughter is working with D. melanogaster
for the third year for a science fair project.
Beginning about 4 to 6 weeks ago about half of the new
cultures we made die within a few days. We are using
a commercial media from Conn Valley Biological Supply.
The affected cultures have a tan colored, mucoid
substance on the surface of the media. They also have
a terrible odor. The media has mold inhibitors so we
suspect a bacterial contaminant. We submitted
cultures for bacterial identification, but the results
are not in yet. Any thoughts on what might cause this
die off?
Ben Haning


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In article <[Only registered users see links. ].net>,
The Hanings <[Only registered users see links. ]> wrote:


Almost certainly bacterial, from your description. You might try more
frequent flips, so there's less of an initial bacterial load, giving the
relatively few larvae a better chance, but I'd toss in some antibiotics
for a generation and see if that clears up the problem.

I don't know how things are in your part of the world, but I gave up on
Carolina medium when I worked in Nashville -- too many mold spores in
the air, so I'd routinely end up losing 1/3 to 1/2 of my vials to mold.
Whether their mold inhibitors were dead, inadequately mixed in, or just
inadequate I don't know, but I switched to cooking my own food and
haven't had a problem since. Impractical if your daughter's doing her
project at home, but I thought I'd mention it.

Chris Jones