5-FOA Medium (5-Fluoroorotic Acid Medium), 5-FOA Plate, 5-FOA Selection

5-FOA (5-Fluoroorotic Acid) Medium and Agar Plate Recipe

Following recipe makes 1 liter 5-FOA plates:

Step-1: Autoclave 20 grams of agar in 750 ml double distilled water.
Step-2: Add followings into a glass beaker, and bring to 250 ml with double distilled water.

Ammonium Sulfate	5.0 g
Yeast nitrogen base without amino acid	1.7 g
Dextrose	20 g
Necessary nutritional supplements (see note 3)	X g
5-FOA	1.0 g

Warm up 5-FOA mixture in Step-2 at 55-65°C on a heat plate, stir until it dissolves ~30 min-1 h. The solubility of 5-FOA is very low in water; therefore, it is necessary to warm up the solution. Some manufacturers, i.e., US Biological, claim that 5-FOA is resistant to autoclaving. I did not try to autoclave it myself, but you can try it.

After 5-FOA containing mixture in Step-2 is completely dissolved, sterilize it by filter. Place both melted agar and 5-FOA containing solution in a water bath (50-60°C) for one hour. Finally, add 5-FOA solution onto melted agar and pour your plates. Plates may be dried at RT for 48 hours and may be kept at 4°C for long term storage.

Notes:

Do not forget to add Uracil into the plates at 20 mg/L of final concentration (Do not add too much Uracil!).
Never adjust the pH of 5-FOA containing medium. Only protonated form of 5-FOA is permeable. pH of your plates will be very acidic after adding 5-FOA.
Do not add more nutritional supplements than it is necessary; this reduces efficacy of 5-FOA plates. For example, you only need to add His, Leu, Lys and Ura supplements for strain BY4742. These supplements may be added directly from 100x stock solution.
5-FOA is very expensive reagent. I found that US Biological has the cheapest price for 5-FOA.
5-FOA is highly mutagenic to Candida albicans. This may also be the case for budding yeast. I suggest you do not leave yeast colonies on 5-FOA plates for longer than it is necessary. Wellington and Rustchenko, Yeast, 2005, Volume 22, Issue 1, Pages 57-70).

Other sources of 5-FOA is Zymo Research and Sigma. The US Biological sells the cheapest 5-FOA reagent. I do not know if purity of 5-FOA is different from each company. 5-FOA from US Biological worked great for me. Do not waste your money!

Good luck with your experiments!

Posted by Erbay Yigit on 29.June.2008, The Final Day of EURO 2008, Spain vs Germany, 1-0. Last modified on 04.September.2008.