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help with food

John Roote jr32 at mole.bio.cam.ac.uk
Mon May 22 07:31:03 EST 1995

>Dear Drosophilists
>The fly group in the IMBB is facing a serious food problem and we'd be very
>greatful if you had any suggestions on how to solve it. Basically, our
>food works fine if the stock/cross is healthy and we put a good number
>of females per vial (6-8 rather than the 1-2 suggested in Kathy Matthews'
>recent posting). However, 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. So,
>if you have any modifications on the following recipe, we'd like to try them:
>Per 3 litres of water we use:
>70 g  sugar (sucrose)
>170 g  yeast (baker's yeast cake previously autoclaved to make sure it's
> dead)
>30 g  agar
>200 g  cornflour
>+ 50 ml of 10% Nipagin (0.17% final)
>The food is usually used fresh (<4 days after cooking - meanwhile stored
>in the coldroom).
>Thank you for your help
>Christos Delidakis
>Inst. of Molecular Biology & Biotechnology
>Heraklion, Greece

Bacterial slime grows well on media made with sucrose. The problem is
solved by replacing sucrose with dextrose.

John Roote.

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