NEB® Stable Competent E. coli (High Efficiency)

NEB does not add a dry ice surcharge to our competent cell shipments.

Now supplied with outgrowth medium optimized for NEB 10-beta & NEB Stable Competent E.coli ; please do not use SOC outgrowth medium.
Catalog #SizeConcentrationPriceQtyAdd to Cart
C3040I6 x 0.2 ml/tube$237.00Add to Cart
C3040H20 x 0.05 ml/tube$308.00Add to Cart
Cloning Strains


Chemically competent E. coli cells suitable for high efficiency transformation and isolation of plasmid clones containing repeat elements.


  • Transformation efficiency:
    1-3 x 10cfu/µg pUC19 DNA
  • Recommended host strain for cloning genes into retroviral/ lentiviral vectors 
  • Recommended for cloning of direct repeats and inverted repeat sequences
  • Reduced recombination of cloned DNA (recA1)
  • Efficient transformation of methylated DNA derived from eukaryotic sources or unmethylated DNA derived from PCR, cDNA and many other sources [mcrAΔ(mrr-hsdRMS-mcrBC)]
  • Activity of nonspecific endonuclease I (endA1) eliminated for highest quality plasmid preparations
  • Resistance to phage T1 (fhuA)
  • Suitable for blue/white screening with vectors capable of alpha-complementation


F' proA+B+ lacIq ∆(lacZ)M15 zzf::Tn10 (TetR) ∆(ara-leu) 7697 araD139 fhuA ∆lacX74 galK16 galE15 e14-  Φ80dlacZ∆M15 recA1 relA1 endA1 nupG rpsL (StrR) rph spoT1 ∆(mrr-hsdRMS-mcrBC)

Reagents Supplied

The following reagents are supplied with this product:

Store at (°C)Concentration
pUC19 Vector-200.05 ng/μl
NEB® 10-beta/Stable Outgrowth Medium4

Advantages and Features


  • High quality plasmid preparations due to endA mutation
  • Rapid growth recA strain
  • T1 phage resistance (fhuA)
  • Value pricing
  • Free of animal products


  • Cloning unstable inserts
  • Isolating and propagating retroviral/ lentiviral clones
  • Compatible with NEBuilder HiFi DNA Assembly, Gibson Assembly reactions as well as ligation reactions

NEB Stable enables the isolation of plasmid clones containing repetitive DNA elements:

Plasmid pUC-5xREP contains five 32-bp repeats, making it unstable in a recombination-proficient strain. A) NEB Stable competent cells or B) Stbl3 competent cells were transformed with 2 µl of a pUC-5xREP Gibson Assembly reaction containing 2.2 ng (0.00125 pmol) pUC19 vector and approximately 1 ng (0.0028 pmol) 5xREP insert. Transformed cultures were plated on LB plates containing 100 µg/ml ampicillin and incubated overnight at 30°C. The next day, colony PCR was performed using M13/pUC polylinker primers to analyze 5xREP insert stability. Figure 1 shows the results of analyzing 33 independent colonies. The correct full-length amplicon is 623bp. 
Effect of outgrowth medium on transformation efficiency

50 μl of NEB Stable competent E. coli was transformed with 100 pg of pUC19 control DNA following the provided High Efficiency Transformation Protocol with the exception of varying the outgrowth medium. NEB 10-beta/Stable Outgrowth Medium delivers the highest transformation efficiency.

Properties and Usage

Antibiotics for Plasmid SelectionWorking Concentration
Ampicillin100 μg/ml
Carbenicillin100 μg/ml
Chloramphenicol33 μg/ml
Kanamycin30 μg/ml

Storage Temperature


Shipping Notes

  • Ships on dry ice

Antibiotic Resistance

  • tetracycline
  • streptomycin


  1. STORAGE AND HANDLING: Competent cells should be stored at -80°C. Storage at -20°C will result in a significant decrease in transformation efficiency. Cells lose efficiency whenever they are warmed above -80°C, even if they do not thaw.
  2. CAUTION: This product contains DMSO, a hazardous material. Review the MSDS before handling.


  1. What are the strain properties (C3040)?
  2. What is the shelf-life for this strain?
  3. Which strain of Competent E.coli should I use for general cloning?
  4. Are NEB Stable Competent E. coli cells suitable for transformation of large plasmids and large NEBuilder® HiFi, Gibson Assembly or Golden Gate Assembly products?
  5. How should I calculate the transformation efficiency (C3040)?
  6. What is the optimal heat shock for this strain? (C3040)
  7. What volume of DNA can be added into chemically competent cells?
  8. Is NEB Stable suitable for larger plasmid transformations?
  9. Is NEB Stable a substitute for Stbl2 or Stbl3?
  10. What type of competent cells are suitable for transformation of DNA constructs created using NEBuilder® HiFi DNA Assembly Master Mix?
  11. How should I store the NEB 10-beta/Stable Outgrowth Medium?


  1. 5 Minute Transformation Protocol (C3040)
  2. High Efficiency Transformation Protocol (C3040I)
  3. High Efficiency Transformation Protocol (C3040H)
  4. Protocol for cloning DNA containing repeat elements (C3040)

Selection Charts

Usage Guidelines & Tips

Interactive Tools

Quality Control

Quality Control Assays

The following Quality Control Tests are performed on each new lot and meet the specifications designated for the product. Individual lot data can be found on the Product Summary Sheet/Datacard or Manual which can be found in the Supporting Documents section of this page. Further information regarding NEB product quality can be found here.
  • Transformation Efficiency:
    The competent cells are tested for transformation efficiency and pass minimum release criteria. Transformation efficiency is defined as the number of colony forming units (cfu) which would be produced by transforming 1 μg of plasmid into a given volume of competent cells.

Certificate of Analysis

The Certificate of Analysis (COA) is a signed document that includes the storage temperature, expiration date and quality control's for an individual lot. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]_[Lot Number]


The Specification sheet is a document that includes the storage temperature, shelf life and the specifications designated for the product. The following file naming structure is used to name these document files: [Product Number]_[Size]_[Version]

Safety Data Sheet

The following is a list of Safety Data Sheet (SDS) that apply to this product to help you use it safely.