This article offers a quick introduction about super optimal broth with catabolite repression or SOC medium (competent cell recovery medium), the reason to use of it after competent cell transformation, a protocol to prepare this medium, and alternative media.
In this Article:
What is SOC Medium?
Super optimal broth with catabolite repression medium or SOC medium is a microbial growth medium, used for providing nutrients and supporting the recovery of bacterial cells following transformation.
Why SOC Medium is Used in Transformation?
Transformation involves perforation of competent cells to allow DNA to enter. The heat-shock step involves quickly cooling and heating cells to create temporary pores, whereas an electric pulse causes temporary holes in the cell membrane.
To help transformed E. coli cells recover from the stress of pore formation, these cells need to live in the best growing environment. Special media, such as SOC medium, containing all nutritional requirements and growth factors, allows the transformed cells to recover optimally.
In the SOC medium, tryptone and yeast extract provide E. coli with a source of carbon and nitrogen, in addition, the medium contains minerals, vitamins and amino acids. Sodium chloride and potassium chloride in the medium maintain ion transport and osmotic balance. Magnesium sulfate is a source of magnesium ions required for some enzymatic reactions. Glucose is an additional source of carbon and energy for metabolism, supporting faster recovery and growth of E. coli.
This combination of salts, magnesium and glucose in the SOC medium stabilizes the transformed cells and supports plasmid uptake (Lessard, 2013). As a result, growing E. coli after transformation in this medium also increases the transformation efficiency.
How to Make SOC Medium?
Below is a protocol to make 100 ml of SOC medium:
- In 95 ml of dH2O, add and dissolve:
2.0 g tryptone
0.5 g yeast extract
1 ml of 1M NaCl
0.25 ml of 1M KCI
- Adjust to pH 7.0.
- Autoclave and allow it to cool to temperature below 60°C.
- Add 1 ml of filter-sterilized 2M Mg+2 (1M MgCl2 + 1M MgSO4).
- Add 1 ml of filter-sterilized 2M glucose solution.
- Add sterile dH2O to a final volume of 100 ml.
How to Store SOC Medium?
For immediate use, store it at room temperature. For long-term use, store it at 4°C.
Alternative Media for SOC Medium
After transforming competent cells, you can also use SOC medium with regular LB medium. However, the cell recovery results for your transformed E. coli can be suboptimal. Therefore, to achieve the best outcomes for E. coli recovery after transformation, use Competent Cell Recovery Medium.
What is Competent Cell Recovery Medium?
GoldBio Competent Cell Recovery Medium is a growth medium with enhanced SOC formulation, used after E. coli transformation. With this formulation, GoldBio Recovery Medium helps you to achieve the best possible recovery efficiency for your transformed cells.
How to Store Competent Cell Recovery Medium?
After receiving GoldBio Recovery Medium, store the medium at 4°C. If stored properly, the medium should be stable for at least 1 year.
How to Use Competent Cell Recovery Medium?
To use the Recovery Medium, add the medium to freshly transformed E. coli cells and incubate for up to 1 hour.
Competent Cell Recovery Medium (Catalog No. CC-300)
GoldBio Competent Cell Recovery Medium is compatible with:
DH10B Chemically Competent E. coli Cells (Catalog No. CC-100)
DH5-alpha Chemically Competent E. coli Cells (Catalog No. CC-101)
BL21 Chemically Competent E. coli Cells (Catalog No. CC-102)
BL21 (DE3) Chemically Competent E. coli Cells (Catalog No. CC. 103)
DL39 (DE3) Chemically Competent E. coli Cells (Catalog No. CC-104)
DH10B Electrocompetent E. coli Cells (Catalog No. CC-200)
DH10B-Pro™ Electrocompetent E. coli Cells (Catalog No. CC-201)
DH5-alpha Electrocompetent E. coli Cells (Catalog No. CC-203)
BL21 (DE3) Electrocompetent E. coli Cells (Catalog No. CC-204)
Bren, A., Park, J. O., Towbin, B. D., Dekel, E., Rabinowitz, J. D., & Alon, U. (2016). Glucose becomes one of the worst carbon sources for E.coli on poor nitrogen sources due to suboptimal levels of cAMP. Scientific Reports, 6(1). https://doi.org/10.1038/srep24834.
Hanahan, D. (1983). Studies on transformation of Escherichia coli with plasmids. Journal of molecular biology, 166(4), 557-580.
Nutrition and Growth of Bacteria. (2012). Textbook of bacteriology. http://textbookofbacteriology.net/nutgro.html
Radchenko, M. V., Tanaka, K., Waditee, R., Oshimi, S., Matsuzaki, Y., Fukuhara, M., Kobayashi, H., Takabe, T., & Nakamura, T. (2006). Potassium/Proton Antiport System of Escherichia coli. Journal of Biological Chemistry, 281(29), 19822–19829. https://doi.org/10.1074/jbc.m600333200.