I can remember times in the past when difficulties like you describe have
happened. The "sticky culture syndrome" with dying flies suggests a
secondary bacterial contamination of the cultures by an unknown pathogen.
That is, all your ingredients in the culture may be OK but contamination
occurs, perhaps from non-sterile cotton or plastic plugs or caps or even
from improperly sterilized glassware or plastic. If I recall correctly, the
lethal vials showed a glistening, syrupy stuff quite unlike what is
sometimes associated with yeast growth. Mold inhibitors seem to have little
or no effect. Another symptom of this (definitely traceable to non-sterile
glassware), is the searation of the food medium from the glass, causing
loosening and falling of the medium when flies are transferred. Our main
approach was to assure everything was sterile. We also had some success in
eliminating the problem with the use of streptomycin in various ways, at
least for a generation or two.
Some contamination of the cornmeal ingredient by bacteria or pesticides is
always a source of suspicion. Some of it surely contains DDT but your
discription sounds like what we called a "bacterial attack" (just
guesswork, of course); no one to my knowledge has tried to isolate an
organism. At Texas for years they were very carfeful to use a particular
brand of cornmeal: sorry, I don't remember what it was called. But you
might obtain several brands and try them out on some sensitive fly cultures.
Good luck and give my warm regards to Michael Ashburner.
With aloha from here, Hamp Carson
>A number of labs in the UK (Cambridge and London) have reported incidents of
>presumed toxic media. The common symptoms are:
> 1) some crosses or stocks die suddenly and completely, flies die
> 2) normal egg-laying, but embryos die (go brown)
> 3) some embryos die, then all seems fine until 1st/2nd instar larvae
>>Many stocks recover - eggs laid later develop OK, but the culture is
>consequently delayed. Flies transferred from sickly cultures often recover.
>These symptoms are very inconsistent, adjacent vials showing completely
>different levels of 'toxicity'.
>One lab has reported that these symptoms occur on media made with cornmeal,
>but not wheat flour - all other ingredients being identical.
>>I would be very interested to hear of similar experiences elsewhere in the fly
>Michael Ashburner's lab Tel: 44 1223 333982
>Department of Genetics Fax: 44 1223 333992
>>University of Cambridge email:
>jr32 at mole.bio.cam.ac.uk>Downing Street
Hampton L. Carson
Professor Emeritus of Genetics and Molecular Biology
John A. Burns School of Medicine,1960 East-West Road
University of Hawaii, Honolulu, Hawaii 96822 USA