Super Optimal Broth

Super Optimal Broth (SOB medium) is a nutrient-rich bacterial growth medium used for microbiological culture, generally of "Escherichia coli". It was developed by Douglas Hanahan in 1983 and is an adjusted version of the commonly used lysogeny broth. Growth of "E. coli" in SOB or SOC medium results in higher transformation efficiencies of plasmids [Hanahan D, 1983. Studies on transformation of "Escherichia coli" with plasmids, "J Mol Biol" 166(4):557-80.] [ [http://www.sigmaaldrich.com/catalog/search/ProductDetail/SIGMA/S1797 SOC Medium] ] .

Super Optimal broth with repression (SOC) is SOB with added glucose [ [http://www.protocol-online.org/biology-forums/posts/10626more1.html] ] .

Composition

(Figures in brackets are the weight required to create 1 litre of medium)

OB

* 2% w/v bacto-tryptone (20g)
* 0.5% w/v bacto-yeast extract (5g)
* 8.56mM NaCl (0.5g) or 10mM NaCl (0.584g)
* 2.5mM KCl (0.186g)
* _ddH₂O to 1000 mL [ [http://www.changbioscience.com/protocols/recipe/SOCmedium.htm SOC medium] ] .

OC

In addition to the SOB contents, SOC also contains
* 10mM MgCl₂ (0.952g)
* 20mM glucose (3.603g)

Some users also add
* 10mM MgSO₄ [ [http://www.sigmaaldrich.com/catalog/search/ProductDetail/SIGMA/S1797 SOC medium] ] (1.204g)

Alternatively, SOC can be made by adding small amounts of concentrated magnesium chloride and glucose solutions to pre-prepared SOB.

pH adjustment

For maximum effectiveness, SOB/SOC media should have its pH adjusted to 7.0 by adding concentrated sodium hydroxide.

Finally, the medium should be autoclaved at 121°C to ensure sterility.

References