Science Buddies: "Ask an Expert"

I have recently been making media for fruit flies, except after a day or two it starts producing mold. I have used different vials and I made sure the tools I used were sterile. Any tips or suggestions, thank you.

Hi - I used to make fruit fly media when I was in college for a genetics lab. The media we used was from a science supply company and I know it had a mold inhibitor in it. I checked on line and found several reference to home made media that all used some ingredient to inhibit mold. One recipe can be found at:

http://voices.yahoo.com/recipe-fruit-fl ... 26364.html

Good luck with your project!

Hello Yvette,

Thank you very much for the feedback, I did some research and heard Methylparaben was good at preventing mold. Do you have any experience using methylparaben?

Hi - no, I do not have experience using methylparaban. Do you have time to purchase a lab grade medium that comes ready to mix already containing the mold inhibitor? Or try the recipe with the vinegar?

Good luck!

Hi Gioro,

I would avoid the use of methyl paraben as a preservative in your fruit fly medium as it is estrogenic and at certain doses can be toxic to the fly larvae. There is an accumulating body of evidence that it can also promote cancer in humans.

Gu Wei (2009), Toxicity and Estrogen Effects of Methyl Paraben on Drosophila melanogaster, Food Science 30 (1): 252–254.

Wróbel AM, Gregoraszczuk EL. Differential effect of methyl-, butyl- and propylparaben and 17β-estradiol on selected cell cycle and apoptosis gene and protein expression in MCF-7 breast cancer cells and MCF-10A non-malignant cells. J Appl Toxicol. 2014 Jan 30. doi: 10.1002/jat.2978.

Many cosmetics are starting to advertise as being paraben-free.

The medium that Yvette suggested is a good one and uses vinegar as an acidifying agent. The lower pH inhibits mold growth.

When i made Drosophila medium in school we used corn meal instead of potato flakes and boiled it and let it cool before adding the yeast. You have to stir the mixture while it is heating so that it doesn't burn, but i think maybe the boiling kills some of the mold spores. Our medium was fine for several weeks with no mold and the flies grew and multiplied well.

Hope this helps you and your flies.

Sybee