YPD

YPD, short for Yeast extract Peptone Dextrose, is a non-selective, nutrient-rich growth medium used to culture yeasts in microbiology and molecular biology. It supports robust growth of Saccharomyces cerevisiae and many other yeasts and fungi, making it a standard baseline medium for routine maintenance, plasmid propagation, fermentation studies, and general yeast work.

Typically prepared as a liquid broth containing yeast extract (about 1% w/v), peptone (about 2% w/v), and dextrose or glucose (about 2% w/v) per liter of water, with the pH adjusted near 5.5–6.0 before sterilization. For solid medium, agar is added (commonly 2% w/v) to form YPD agar. The medium is sterilized by autoclaving and can be supplemented after cooling with additives compatible with yeast, such as adenine for auxotrophic strains, though these are not required for routine growth. Antibiotics are rarely needed in YPD since it is non-selective, but selective variants exist by combining YPD with specific agents.

Uses: YPD supports rapid, non-selective growth and is frequently used to recover yeast from stocks, grow cultures for plasmid extraction, or as a general growth medium before applying selective conditions. It is also used as a foundation for other media by adding selective agents to create selective plates or broths.

History and overview: YPD is among the most commonly used rich media in yeast research, dating from mid-20th century work on yeast cultivation. Its simplicity and robust performance contributed to its status as a standard in laboratories worldwide.