SD + 5-Fluorocytosine Medium
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1. Dissolve 6.7 g of yeast nitrogen base with ammonium sulfate and without amino acids, 20 g of dextrose, and 5-fluorocytosine (5FC) in 100 mL of deionized water. Filter-sterilize.
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In the absence of adenine and uracil, the final concentration of 5FC should be 100 µm. In the presence of adenine and uracil (based on the genotype of the yeast strain being plated), the final concentration of 5FC should be 1 mm. 5FC solutions should be made up fresh to limit spontaneous deamination to 5FC, which reduces the effectiveness of the counter selection for resistance to 5FC.
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2. Autoclave 20 g of Bacto agar in 900 mL of deionized water.
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3. Add the filter-sterilized solution to the autoclaved agar; mix thoroughly, and pour the medium into Petri dishes.
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5FC-containing media are best used fresh but, if necessary, can be stored for several months at 4 °C in the dark.
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This recipe is adapted from Hartzog et al. (2005).
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