Competent Cell Selection Guide

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 and formats of NEB’s strains to help select the optimal strain for a particular experiment. The free online tool, NEBcloner can also be used to help select competent cells. For more information, please visit Cloning Competent Cell Strains or E.coli Expression Strains.

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

 

Cloning Strain Properties

STRAIN PROPERTIES FEATURES CHEMICAL TRANSFORMATION EFFICIENCY
(cfu/μg)
ELECTROCOMPETENT TRANSFORMATION EFFICIENCY
(cfu/μg)
AVAILABLE FORMATS(7) OUTGROWTH MEDIUM & CONTROL PLASMID INCLUDED? STRAIN BACKGROUND LIBRARY CONSTRUCTION BLUE/WHITE SCREENING lacIq endA(2) recA DRUG RESISTANCE(5) METHYLATION PHENOTYPE
dam/dcm
  • Dam/Dcm methyltransferase free plasmid growth
1-3 x 106 n/a 50, 200 K12 cam, str, nit Dam , Dcm , M. EcoKI+
NEB Turbo (High Efficiency)
  • Fastest growth – colonies visible after 6.5 hours
  • Plasmid preparation after 4 hours
1-3 x 109 n/a 50, 200 K12 nit Dam +, Dcm+, M. EcoKI
NEB 5-alpha (High Efficiency)
  • Versatile cloning strain
  • DH5α™ derivative
1-3 x 109 (8) > 1 x 1010 50, 200, 96, 384, Strips  K12 none Dam+, Dcm+,M. EcoKI+
NEB 5-alpha F´ Iq (High Efficiency)
  • Toxic gene cloning
  • F´ strain with extremely high transformation efficiency
1-3 x 109 n/a 50, 200 K12 tet Dam+, Dcm+,M. EcoKI+
NEB 10-beta (High Efficiency)
  • Large plasmid and BAC cloning
  • DH10B™ derivative
1-3 x 109 (9) > 2x 1010 50, 200, 96 K12 str Dam +, Dcm+,M. EcoKI
NEB Stable (High Efficiency)
  • Cloning unstable inserts
  • Isolating and propagating retroviral/lentiviral clones
1-3 x 109 n/a 50, 200 K12 tet, str Dam +, Dcm+,M. EcoKI
NEB 5-alpha (Subcloning Efficiency)
  • Ideal for subcloning efficiency transformations, such as plasmid transformation or routine subcloning
> 1 x 106 n/a 400 K12   none Dam+, Dcm+,M. EcoKI+

 

Protein Expression Strain Properties

FEATURES CHEMICAL TRANSFORMATION EFFICIENC
(cfu/μg)
AVAILABLE FORMATS(7) OUTGROWTH MEDIUM & CONTROL PLASMID INCLUDED? STRAIN BACKGROUND LIBRARY CONSTRUCTION lacIq lysY endA(2) PROTEASE DEFICIENT(3) T7 RNA POLYMERASE CYTOPLASMIC DISULFIDE BOND FORMATION (4) DRUG RESISTANCE(5) METHYLATION PHENOTYPE
NEBExpress
  • Versatile non-T7 expression strain
  • Protease deficient
0.6-1 x 109 50, 200 B nit Dam +, Dcm , M.EcoKI
BL21(DE3)
  • Routine T7 expression
1-5 x 107 50, 200 B none Dam+,Dcm, M.EcoKI
Lemo21(DE3)
  • Tunable T7 expression for difficult targets
1-3 x 107 50 (1) B cam Dam+,Dcm, M.EcoKI
NiCo21(DE3)
  • Improved purity of target proteins isolated by IMAC
1-5 x 107 50 B none Dam+,Dcm, M.EcoKI
BL21
  • Routine non-T7 expression
1-5 x 107 50 B   none Dam+,Dcm, M.EcoKI
T7 Express
  • Most popular T7 expression strain
  • Protease deficient
0.6-1 x 109 50, 200 B nit Dam+,Dcm, M.EcoKI
T7 Express lysY
  • T7 expression
  • Protease deficient
  • Better reduction of basal expression
0.6-1 x 109 200 B cam, nit Dam+,Dcm, M.EcoKI
T7 Express lysY/Iq
  • T7 expression
  • Protease deficient
  • Highest level of expression control
0.6-1 x 109 200 B cam, nit Dam+,Dcm, M.EcoKI
SHuffle T7
  • T7 expression/K12 strain
  • Enhanced capacity to correctly fold proteins with multiple disulfide bonds in the cytoplasm
1 x 106 50 K12 str, spec, nit Dam+,Dcm+, M.EcoKI+
SHuffle Express
  • Protease deficient/B strain
  • Enhanced capacity to correctly fold proteins with multiple disulfide bonds in the cytoplasm
1 x 107 50 B spec(6), nit Dam+,Dcm, M.EcoKI
SHuffle T7 Express
  • T7 expression
  • Protease deficient/B strain
  • Enhanced capacity to correctly fold proteins with multiple disulfide bonds in the cytoplasm
1 x 107 50 B spec(6), nit Dam+,Dcm, M.EcoKI
SHuffle T7 Express lysY
  • T7 expression
  • Protease deficient/B strain
  • Tightly controlled expression of toxic proteins
  • Enhanced capacity to correctly fold proteins with multiple disulfide bonds in the cytoplasm
1 x 107 50 B cam, spec(6), nit Dam+,Dcm, M.EcoKI
NEBExpress Iq
  • Control of IPTG induced expression from Plac, Ptac, Ptrc and T5lac
  • Protease deficient
0.6-1 x 109 200 B cam, nit Dam+,Dcm, M.EcoKI

(1) Rhamnose solution is provided instead of SOC; control plasmid is included.
(2) Important for high-quality plasmid preparation.
(3) Lacks Lon and OmpT protease activity.
(4) Constitutively expresses a chromosomal copy of the disulfide bond isomerase DsbC.
(5) nit = nitrofurantoin, tet = tetracycline, cam = chloramphenicol, str = streptomycin, spec = spectinomycin
(6 )Resistance to low levels of streptomycin may be observed.
(7) Legend 50 = 50 µl tubes; 200 = 200 µl tubes; 96 = 96 well plate; 384 = 384 well plate; strips = 96 tube strips (50 µl/tube); 400 = 400 µl tubes
(8) 1-5 x 108 for R-format.
(9) 1-3 x 108 for P-format.