YMA Agar (Yeast Extract Mannitol Agar with Calcium Carbonate)

YMA Agar (Yeast Extract Mannitol Agar with CaCO₃) is a selective medium widely used for the isolation, cultivation, and differentiation of Rhizobium species (root nodule bacteria). The medium contains mannitol as a carbon source, yeast extract as a nitrogen and vitamin supply, and calcium carbonate for pH stabilization and detection of acid production. The presence of agar solidifies the medium, making it suitable for plate culture and colony morphology observation.

Applications:

• Cultivation and maintenance of Rhizobium spp.

• Study of root nodule bacteria in symbiotic nitrogen fixation

• Screening of acid-producing colonies (dissolution of CaCO₃)

• General microbiological research on soil bacteria

Specifications:

• Form: Powder, 250 g/bottle

• Storage: Room temperature

• Shelf Life: 3 years

Formula (per liter):

• Mannitol – 10.0 g

• CaCO₃ – 4.0 g

• KH₂PO₄ – 0.5 g

• Yeast Extract – 0.4 g

• MgSO₄·7H₂O – 0.2 g

• NaCl – 0.1 g

• Agar – 15.0 g

• Final pH: 6.8 ± 0.2 (25℃)

Preparation Instructions:

1. Weigh 30.2 g of the medium and suspend in 1 liter of distilled or deionized water.

2. Heat and boil for at least 1 minute until the agar is completely dissolved.

3. Dispense into suitable containers.

4. Sterilize by autoclaving at 121℃ for 15 minutes.

5. Cool to approximately 50℃, shake gently, and pour plates.

6. Allow to solidify and store under sterile conditions for use.