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  • Strain Properties

    There are many properties to consider when choosing a strain for your experiments. Requirements such as plasmid preparation, blue/white screening, cytoplasmic disulfide bond formation, and fast colony growth necessitate specific strain choices. The following selection chart highlights the characteristics of NEB’s strains to help select the optimal strain for a particular experiment.

    CAUTION: Chemically Competent E. coli contain DMSO, a hazardous material. Review the MSDS before handling.

    ProductNEB #Transform Efficiency (cfu/µg)⁽¹⁾StrainT1 Phage ResistantLibrary Construction⁽²⁾Cloning/Sub CloningBlue/White ScreeninglaclqlysYEndonucleaseI Deficient⁽³⁾Protease Deficient⁽⁴⁾F'RecA¯T7 RNA PolymeraseCytoplasmic disulfide bond formation⁽⁵⁾Drug Resistance⁽⁶⁾
    Cloning Strains
    NEB Turbo Competent E. coli (High Efficiency)C29841-3x109K12nit
    NEB 5-alpha Competent E. coli (High Efficiency)C29871-3x109K12none
    NEB 5-alpha F'Iq Competent E. coli (High Efficiency)C29921-3x109K12tetracycline
    NEB 10-beta Competent E. coli (High Efficiency)C30191-3x109K12str
    dam-/dcm- Competent E. coliC29251-3x106K12cam, str and nit
    Protein Expression Strains
    NEB Express Competent E. coli (High Efficiency)C25230.6-1x109Bnit
    NEB Express Iq Competent E. coli (High Efficiency)C30370.6-1x109Bcam and nit
    T7 Express Competent E. coli (High Efficiency)C25660.6-1x109Bnit
    T7 Express Iq Competent E. coli (High Efficiency)C30160.6-1x109Bcam and nit
    T7 Express lysY Competent E. coli (High Efficiency)C30100.6-1x109Bcam and nit
    T7 Express lysY/Iq Competent E. coli (High Efficiency)C30130.6-1x109Bcam and nit
    T7 Express Crystal Competent E. coli (High Efficiency)C30220.6-1x109Bnit
    SHuffle® T7 Competent E. coliC30261 x 106K12str and spec
    SHuffle® Express Competent E. coliC30281 x 107Bspec
    SHuffle® T7 Express Competent E. coliC30291 x 107Bspec⁽⁷⁾
    SHuffle® T7 Express lysY Competent E. coliC30301 x 107Bcam and spec⁽⁷⁾
    BL21 Competent E. coliC25301-5x107B
    BL21(DE3) Competent E. coliC25271-5x107B
    NiCo21(DE3) Competent E. coliC25291-5x107B
    Lemo21(DE3) Competent E. coliC25281-3x107Bcam
    1. TE given are for high-efficiency chemically competent strains. TE for electrocompetent strains are 1-4 x 1010cfu/mg. TE for subcloning strains are >1 x 106.
    2. Restriction-deficient strain.
    3. Important for plasmid preparation.
    4. Lacks Lon and OmpT protease activity
    5. Constitutively expresses a chromosomal copy of the disulfide bond isomerase DsbC.
    6. nit = nitrofurantoin, tet = tetracycline, cam = chloramphenicol, str = streptomycin, spec = spectinomycin
    7. Resistance to low levels of streptomycin may be observed.