Home Resources Selection Charts Competent Cell Selection Guide

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) F´    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) n/a 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) F´ 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.