Yeast Mold (YM) Agar is used for cultivating yeasts, molds and other aciduric microorganisms.
SUMMARY AND EXPLANATION
YM Agar and YM Broth are prepared according to the formulae published by Wickerham.1-3 Wickerham suggested that YM Broth acidified to pH 3.0-4.0 be used as an enrichment medium for yeasts from populations also containing bacteria and molds.
Media selectivity may be enhanced through acidification or through addition of selective agents. YM Broth may be acidified prior to sterilization. YM Agar should be sterilized without pH adjustment and sterile acid added to the sterile molten medium cooled to 45-50°C. Acidified YM Agar should not be heated. Antibiotics may be aseptically added to the sterile media. Other fungistatic materials, such as sodium propionate and diphenyl may be added to YM Agar to eliminate molds and permit the enumeration of yeasts in mixed populations.
Yeast extract is a source of trace elements, vitamins and amino acids. Malt extract is a source of carbon, protein and nutrients. Peptone is an additional source of carbon and provides nitrogen and amino acids. Dextrose provides carbon. Agar is the solidifying agent.