YPD or YEDP (Yeast Extract Peptone Dextrose) medium

• 20 g/L peptone or tryptone
• 10 g/L yeast extract
• 20 g/L glucose (or other sugar)
• Optional: 20 g/L agar for solid medium (*)

Prepare maximum half of the flask volume, so no more than 500 mL in an 1 L flask. This prevents boil over and makes it easier to pour from the bottle. Mix components in a Schott flask, add water and shake well to dissolve all the the powder. Clean the balance if dirty. Clean the spoons and put them on the drying rack. Use the deionized water. Using the tap water in the lab is also ok. We do not check or set pH for this medium. The dry components can also be mixed in a bottle and prepared using a microwave oven, see YPDpowder.

(*) Mark the flask with AGAR with big letters on the side of the flask.

Add a small piece (0.5 - 1 cm) autoclave tape on the lid. Put the flask on the autoclave trolley and fill in the form. Sr. Luis will put the flask in the 50°C incubator to cool down after autoclaving.

Alternatively, YPD can be made from sterile stock solutions, 50 mL :

• 25 mL P40Y20
• 2 mL Glucose (50% w/v = 500 g/L = 20x)
• Sterile water to 50 mL dH2O

Mix in a sterile 50 mL Falcon tube in a Laminar flow cabinet or next to a Bunsen burner. Ordinary tap water can be used since tap water was used to produce the yeast extract and the peptone in the first place. There is normally no need to set the pH, it should be around 7.

This medium can also be prepared in dry form and then mixed with water and heated using a microwave oven: YPDpowder.

Pour the plates after the medium has cooled down.

Reuse the plastic bag that the plates came from to store the plates.

Antibiotics

Add antibiotics after cooling down the media bottle to ~50°C (cold enough to touch).

Fatty acid supplementation

Add Tween and Myristic acid for growth of fas- mutants. Add the components to the medium before autoclaving. Media becomes slightly cloudy from these ingredients.

YPDlight or 1/2-strength YPD or 0.5xYPD

This is like YPD but with half of the peptone and yeast extract. This medium is good for selection using zeocin or phleomycin which are salt sensitive antibiotics.

• 10 g/L peptone (1/2 of the usual amount, same as LB)
• 5 g/L yeast extract (1/2 of the usual amount, same as LB)
• 20 g/L Glucose
• 20 g/L Agar

ypX

For scoring slow growth it can be an advantage to reduce the yeast extract and peptone to 1/10th of the usual concentration to reduce background growth. The medium below has been successfully used to score slow growth on D-xylose for recombinant yeast strains.

• 1 g/L yeast extract
• 2 g/L peptone
• 20 g/L D-xylose
• 20 g/L Agar

YPE

Like YPD but 2% ethanol instead of glucose. Prepare YPD without glucose, add 20 mL 96 % ethanol after cooling down to <50°C.

• 2% EtOH
• 2% peptone
• 1% yeast extract

YPA

• 2% potassium acetate (KAc)
• 2% peptone
• 1% yeast extract

Excellent for inducing high levels of respiration in cells prior to sporulation (UNIT 13.2).