In article <3899B72A.7B98F2DC at gen.cam.ac.uk>, j.roote at gen.cam.ac.uk wrote:
> 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
> before egg-laying
> 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.
If Hamp Carson is right about the problem being bacterial (although our
bacterial infestations were usually of the milky-white-slime ilk), perhaps
some of these tested-fly-compatible antibiotic combos may help:
We would apply one of 4 combinations of antibiotics to every batch of
food, rotating them to prevent the bacteria from developing resistance.
1) Ampicillin + chloramphenicol (each at 50 ug/ml final) Stock solutions =
each @ 1000x, Amp in water, CAM in EtOH. Mix just before using to avoid
precipitation of the CAM.
2) Gentamycin + Doxycycline (each at 50 ug/ml final) Stock = each @ 1000x
in water, can make as a mixed stock.
3)Amoxicillin + Cefamandole (100 ug/ml and 150 ug/ml respectively) Stock =
each @ 1000x in water, can make as a mixed stock. (pH may need to be
raised slightly for complete suspension.)
4) Hexamethylene tetramine, mandelate salt (= methenamine mandelate)
(4 mg/ml) Stock = 400 mg/ml (Yes, that's 0.4 g/ml!)
Store stock solutions in aliquots at -20oC.
DO NOT add antibiotics to hot food, as this will seriously affect their
potency. Add as a dilution from stock to the surface once the food has
solidified to give the final concentrations shown. For convenience, we
dilute the stocks so that we add 70 ul of solution to vials and 500 ul of
solution to bottles -- note that this enables you to make a single
dilution (assuming your bottles contain about 7 times as much food as the
vials) -- and dry the food as long as needed.
It's something of a pain in the posterior, but so is losing lines. Hope
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