We currently use the following recipe, which we designed ourselves. For 12 litres of food
- Agar 96g
- Polenta 240g
- Fructose 960g
- Brewer's Yeast 1200g
- 12 litres water
- Put the agar and polenta in the pot. Add 8 litres of water and bring to a boil, stirring constantly and vigorously, over highest heat.It is important that the food reach a full boil in order to dissolve the agar.
- Turn the heat to minimum. Add the fructose and the yeast. (We usually mix these two ingredients together before adding them, on the assumption that this reduces clumping.) Simmer 10 minutes with heat on low, continuing constant stirring. Watch to make sure it doesn't boil over!
- Turn off the heat, then add the remaining 4 litres of water, still stirring constantly. The temperature should now be 70°C or just below.
- Allow to cool to below 70°C, then add (still stirring constantly!):
- 60ml 15% Nipagin in ethanol
- 90ml Propionic acid
(Nipagin = Nipagin M = tegosept M = p-hydroxybenzoic acid methyl ester)
- Dispense about 8ml per fly vial.
We have previously used a complex molasses recipe, a very simple sucrose-yeast recipe, and a glucose-yeast recipe. We disliked the molasses recipe because it had so many ingredients; we disliked the sucrose-yeast recipe because we had serious problems with Leuconostoc infections (slimy vials). This recipe seems to work at least as well as the others at supporting life, doesn't get slimy, and is easy to pump.
Depending on the specifics of your experiment, some of the details may vary, but in general, the paper and accompanying video tutorial from the Lazzaro lab provides a valuable guide to injecting flies with bacteria.
Khalil, S., Jacobson, E., Chambers, M. C., Lazzaro, B. P. Systemic Bacterial Infection and Immune Defense Phenotypes in Drosophila Melanogaster. J. Vis. Exp. (99), e52613, doi:10.3791/52613 (2015).
If you are a new member of the fly room (or an old member that needs a reminder!), please refer to this document regarding how we deal with waste in the fly room.