help with food (fwd)

[Terrence Lyttle]

    I have two solutions which you might try.  I am pretty sure you have a 
problem with the bacterium leuconostoc.  The slime is actually the 
polysaccharide coat from the bacterium.  Solution #1 is to switch to 
using dextrose as your sugar source.  Leuconostoc cannot metabolize 
dextrose to make the coat, and since it is the coat that is causing the 
trouble (suffocating the larvae and eggs and dessicating the adults), 
your cultures should go better.  Two problems with this approach are (1) 
after many generations on this sugar source, many fly strains begin to 
weaken (a nutritional problem?), and (2) this does not really eliminate 
the bacterium, so the infection can come back even stronger if you have 
to switch back to a sucrose based food.
   The second solution works better in the long run.  Spray the surface 
of your food after it cools with a suspension of the yeast (live) Candida 
crusiae (you can get this from American Type Culture).  This is an 
excellent food source for Drosophila, grows aggressively, and in our 
hands, quickly outcompetes the bacterial infection, eliminating it as a 
problem after only a couple of generations.  I recommend this approach 
highly.  We use this Candida strain regularly on our cultures now, and 
the flies really love it (it smells good to researchers as well!)  Please 
note that this Candida species is not a problem for humans, in particular 
it does not cause the problem for women that some Candida species are 
responsible for.  Good luck!

 On Sun, 21 May 1995 delidakis at nefeli.imbb.forth.gr wrote:

> 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

Terry Lyttle
Department of Genetics and Molecular Biology
University of Hawaii