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Slime in fly food

oujac at vax.ox.ac.uk oujac at vax.ox.ac.uk
Mon May 22 04:41:03 EST 1995

Christos Delidakis writes:
> ...when we go down to 1-3 females of a not so
> vigorous strain, the culture becomes overrun by some sort of slime, which
> is probably bacteria. A few eggs and 1st instar larvae are usually seen
> dead in the slime. The only way to prevent this infection is to add
> tetracyclin in the food (final concentration 1 ug/ml), but I was wondering
> if there was a solution that doesn't involve the use of antibiotics....
Are you seeding the medium with live yeast after it has been made?  We have had
slime problems too, and the bacteria (?) that cause the problem seem to be
imported on the fresh baker's yeast that we put onto our medium before use.  We
can largely prevent this by using extremely fresh yeast.  In the Ashburner lab
they used to (Michael:  do you still?) use freshly-reconstituted dried yeast,
which is probably bacteria-free.
If slime does appear, we usually see it before putting the flies in the bottle. 
At this stage, it is possible to wipe the medium thoroughly with a tissue to
dry it, which is quite effective.  Despite possible problems with soupy food,
we also find that a high concentration of flies helps this problem.
Ben Yudkin

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