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Culture Media

GCM11.0500 - SOB Medium, 500g



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SOB Medium is a dehydrated powder for the preparation of nutritionally rich liquid medium for the preparation and transformation of E. coli. Transformation requires perforation of bacteria to allow DNA to enter the cell. To survive this process, competent cells need isotonic rich media. SOB Medium is well suited for this role. 

SOB contains all the nutritional requirements for E. coli. Tryptone and Yeast Extract are the sources for carbon, nitrogen, vitamins, minerals, and amino acids essential for growth. Sodium chloride and Potassium chloride supply essential electrolytes for transport and osmotic balance, while Magnesium sulfate serves as a source for magnesium ions.

Formulation (g/L)

  • Tryptone: 20.00
  • Yeast Extract: 5.00
  • NaCl: 0.50
  • MgSO4: 0.96
  • KCl: 0.186
  • Final pH (25°C): 7.0 ± 0.2

Add 26.6g of the dehydrated medium to one liter of distilled water. Mix well and dissolve by heating with regular agitation. Boil for 1 minute in order to dissolve completely. Dispense in appropriate containers and sterilize by autoclaving at 121°C for 15 to 20 minutes. Store at 2-8°C.



  • Optimized for the preparation and transformation of competent cells 
  • Isotonic rich medium
  • Contains all the nutritional requirements for E. coli



  • SOB Medium, 500g