View source for Super Optimal Broth

{{Short description|Culture medium used in microbiology}}
'''Super Optimal Broth''' ('''SOB medium''') is a [[nutrient]]-rich bacterial [[growth medium]] used for [[microbiological culture]], generally of ''[[Escherichia coli]]''. This nutrient-rich microbial [[broth]] contains [[peptides]], [[amino acid]]s, water soluble [[vitamins]] and [[glucose]] in a low-salt formulation. It was developed by [[Douglas Hanahan]] in 1983 and is an adjusted version of the commonly used LB medium ([[lysogeny broth]]). Growth of ''[[Escherichia coli|E. coli]]'' in SOB or SOC medium results in higher [[Transformation (genetics)|transformation]] efficiencies of [[plasmid]]s.<ref>{{Cite journal
| last1 = Hanahan | first1 = D.
| title = Studies on transformation of [[Escherichia coli]] with plasmids
| journal = Journal of Molecular Biology
| volume = 166
| issue = 4
| pages = 557–580
| year = 1983
| pmid = 6345791
| doi=10.1016/S0022-2836(83)80284-8
}}</ref><ref name=SA>[http://www.sigmaaldrich.com/catalog/search/ProductDetail/SIGMA/S1797 SOC Medium]</ref>
SOC medium can also be used to regenerate ''[[Klebsiella oxytoca]]'' [[Strain (biology)|strains]] for the improved transformation efficiency.
'''Super Optimal''' broth with [[Catabolite repression|'''Catabolite''' repression]] ('''SOC''') is SOB with [[glucose]] added to the culture medium as preferred carbon and energy source (''i.e.'', rapidly metabolizable).<ref name="protocol-online.org">http://www.protocol-online.org/biology-forums/posts/10626more1.html {{Dead link|date=February 2022}}</ref>
== Composition ==
Figures in parentheses are the masses of reagents required to prepare 1 liter of medium.
=== SOB ===
* 2 % w/v [[tryptone]] ([[tryptic]] peptides from the [[casein]] [[hydrolysis]] by [[trypsin]]) (20 g)
* 0.5 % w/v [[yeast extract]] (5 g)
* 8.56 mM [[Sodium chloride|NaCl]] (0.5 g) or 10 mM NaCl (0.584 g)
* 2.5 mM [[Potassium chloride|KCl]] (0.186 g)
* [[Purified water#Double distillation|Doubly distilled H<sub>2</sub>O]] to 1000 mL<ref>[http://www.changbioscience.com/protocols/recipe/SOCmedium.htm SOC medium]</ref>
* 10 mM [[Magnesium chloride|MgCl<sub>2</sub>]] (anhydrous: 0.952 g; hexahydrate: 2.033 g) and 10 mM [[Magnesium sulfate|MgSO<sub>4</sub>]] (anhydrous:1.204 g; heptahydrate: 2.465 g)<ref name=SA/>
=== SOC ===
In addition to the SOB contents, SOC also contains 20 mM [[glucose]] (3.603 g).
Alternatively, SOB and SOC can be prepared 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]].<ref name="protocol-online.org" /> The original literature states that the pH of the final medium should be between 6.8 and 7.0.
== Sterilization ==
Finally, the SOB medium should be [[autoclave]]d at 121&nbsp;°C to ensure [[Sterilization (microbiology)|sterility]]. The components of SOC medium should not be autoclaved together because at elevated temperature glucose can react with the [[tryptic]] peptides (see [[Maillard reaction]]), compromising the quality of the preparation. SOB and magnesium and glucose additive solutions can be autoclaved separately and mixed afterwards to the final concentrations. Complete SOC can be [[Microfiltration|filter sterilized]] through a 0.22&nbsp;μm filter.
== References ==
{{Reflist}}
[[Category:Microbiological media]]
[[Category:American inventions]]