YP Agar Base Medium

YP Agar Base Medium is also used to cultivate Saccharomyces cerevisiae and other yeasts. Yeasts grow well on a medium containing only a minimal amount of glucose and salts. This medium contains glucose (with the addition of dextrose after autoclaving), salts and proteins, which favours the growth of Saccharomyces cerevisiae and reduces growing times. Yeast extract is the source of vitamins, particularly the B-group, essential for bacterial growth. Peptone provides nitrogen, vitamins, minerals and amino acids. Bacteriological agar is the solidifying agent.

Saccharomyces cerevisiae has a genome of 14 Mb containing 6000 genes arranged in 16 chromosomes, which have been completely sequenced, and thus, is a species type in microbiology and genetics studies.

Preparation

Suspend 50 grams of the dehydrated medium in 900 mL of distilled water. Mix well and dissolve by heating with frequent agitation. Boil for one minute until complete dissolution. Sterilize in autoclave at 121 °C for 15 minutes. Cool to room temperature and aseptically add 100 mL of sterile dextrose at 20%. Mix well and dispense into appropriate containers.

Instructions for use

Pour plate method:

1. Deposit 1 mL of the initial suspension and/or diluted sample in an empty Petri dish.
2. Add 12-15 mL of agar cooled to 44-47 °C in each Petri dish and mix gently moving the plate.
3. Allow the plates to solidify and incubate in an inverted position at a temperature of 25 ± 2 °C for 42-48 hours.

Streak plate method:

1. In a Petri dish, add 12-15 mL of molten agar and let it solidify.
2. Inoculate 10 µL of the initial suspension and/or diluted sample.
3. Extend the inoculum with a sterile loop on the agar surface.
4. Incubate the plates in an inverted position at a temperature of 25 ± 2 °C for 42-48 hours.

• Guide to yeast genetics and molecular biology. (1991) Ed. Christine Guthrie & Gerald Fink. Methods in Enzymology vol. 194.
• Current protocols in Molecular Biology. Eds. Ausubel, F. M. Brent, R., Kingston, R, E., Moore, D. D., Seidman, J. G., Smith J. A., and Struhl, K. 13,01.-13.2.10.
• The Yeast Genome Directory (1997, May 29) Nature Supp. to volume 387.
• The condensed protocols from molecular cloning: a laboratory manual / Joseph Sambrook, David W. Russell.