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lynda e
lynda e's picture

Does anyone have the protocol for making what is being called Agar medium S? It must meet both european and us guidelines.


Richard Taylor
Richard Taylor's picture
The media "Agar medium S" is

The media "Agar medium S" is also known as R3A. R3A is an agar supplemented with nutrients, R3A has twice the concentration of nutriants as R2A.

R2A was first described in an article entitled : "A new medium for the enumeration and subculture of bacteria from potable water." by D J Reasoner and E E Geldreich. Appl Environ Microbiol. 1985 January; 49(1): 17.

The Free Full text of the article is in Pubmed Central:

Ingredients of R3A
*1 g/L of yeast extract,
*1 g/L of Difco Proteose Peptone no. 3 (Difco Laboratories)
*1 g/L of Casamino Acids (Difco),
*1 g/L of glucose,
*1 g/L of soluble starch,
*0.6 g/L of K2HPO4,
*0.01 g/L of MgSO4 X 7H2O
*0.6 g of sodium pyruvate,
*30 g/L of agar per liter of laboratory quality water.

Adjust the pH to 7.2 with crystalline K2HPO4 or KH2PO4 and sterilize at 121 degrees C for 15 min.

This is confirmed by a Sifin datasheet:

This is not a fully defined media - it contains a number of natural products - peptone, yeast extract and agar - which makes some regulatory issues more tricky - what guidelines are you required to follow? If you're at an ealry stage of developing something in a heaivly regulated environment you might want to consider the possibilities of a completly defined media.