R2A Agar

R2A Agar

SKU: KM0082 Category: Tag:

R2A agar is used for the enumeration and cultivation of bacteria from drinking water. R2A agar developed by Reasoner and Geldreich is a low nutrient medium that can used in pour plate, spread plate, and membrane filtration methods for heterotrophic plate counts. In combination with a lower incubation temperature and longer incubation period R2A agar stimulates the growth of stressed and chlorine-tolerant bacteria. Traditionally nutritionally rich media have been used for this purpose but these media support the growth of fast-growing bacteria and may suppress slow growing or stressed bacteria found in treated water.
Enzymatic digest of casein, proteose peptone, acid hydrolysate of casein and yeast extract provide the required nitrogen, carbon and vitamins. Glucose is a fermentable carbohydrate. Dipotassium hydrogen phosphate is a buffering agent. Magnesium sulphate is a source of divalent cations and sulphate. Starch and sodium pyruvate aid in the recovery of stressed organisms.


Additional Information

Shelf Life (days)

Storage Temp (°C)

Dehydrated Medium Appearance

Prepared Medium Appearance

Dehydrated Medium Colour

Prepared Medium Colour

Dehydrated PH

Prepared PH

Product Description

Organisms Ref. No Result
Aeromonas hydrophila NCTC 8049 Growth, grey colonies
Pseudomonas aeruginosa NCTC 12903 Growth, grey colonies



Enzymatic digest of casein 0.25
Proteose peptone 0.25
Acid hydrolysate of casein 0.5
Yeast extract 0.5
Glucose 0.5
Starch 0.5
Dipotassium hydrogen phosphate 0.3
Magnesium sulphate 0.05
Sodium pyruvate 0.3
Agar 15.0
Total 18.15
*Adjusted/supplemented as required to meet performance requirements


Suspend 18.15g of the medium in one litre of deionised / purified water. Allow the medium to soak whilst mixing for 10 minutes. Sterilise at 121°C for 15 minutes with frequent stirring to completely dissolve the medium. Cool to 45-50°C and dispense into appropriate sterile containers.