This protocol outlines the steps to make a standard yeast-glucose medium for Drosophila melanogaster cultures. It can be scaled up or down depending on the number of cultures needed.
Prepare Methylparaben Solution: Dissolve 4g of methylparaben in a small amount of ethanol to prevent fungal growth in the medium.
Mix Dry Ingredients: In a large pot, combine the agar, cornmeal, yeast, glucose, and soy flour if using. Mix these dry ingredients thoroughly to ensure even distribution.
Add Water: Slowly add 1 liter of water to the dry ingredients while stirring continuously to prevent lumps. Ensure that the mixture is homogeneous.
Cook the Mixture: Heat the mixture on a stove or hot plate, stirring constantly to prevent sticking and burning. Bring the mixture to a boil, then simmer for about 10 minutes until the agar is completely dissolved, and the mixture thickens.
Cool Down: Allow the mixture to cool down to approximately 60°C (140°F). This is important to prevent the degradation of some components, especially the methylparaben.
Add Preservatives: Once the mixture has cooled to the appropriate temperature, add the methylparaben solution and a few drops of propionic acid to the mixture. Stir thoroughly to ensure even distribution.
Dispense: Carefully pour the medium into sterile culture bottles or vials. The amount of medium you add will depend on the size of the container and your experimental needs.
Sterilize: If not using immediately, the prepared diet can be sterilized in an autoclave and then stored at room temperature until needed. Ensure the bottles are loosely capped before autoclaving to avoid pressure build-up.
Cool and Store: Allow the medium to cool and solidify before capping the bottles tightly. Store the prepared diet in a cool, dark place until ready to use.
Inoculate with Flies: Once the medium is prepared and cooled, you can add fruit flies to the vials or bottles for rearing or experimental use.