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.

Product NEB # Transform Efficiency (cfu/µg)⁽¹⁾ Strain T1 Phage Resistant Library Construction⁽²⁾ Cloning/Sub Cloning Blue/White Screening laclq lysY EndonucleaseI Deficient⁽³⁾ Protease Deficient⁽⁴⁾ F' RecA¯ T7 RNA Polymerase Cytoplasmic disulfide bond formation⁽⁵⁾ Drug Resistance⁽⁶⁾
Cloning Strains
NEB® Turbo Competent E. coli (High Efficiency) C2984I
C2984H
1-3x109 K12 nit
NEB® 5-alpha Competent E. coli (High Efficiency) C2987U
C2987R
C2987P
C2987I
C2987H
1-3x109 K12 none
NEB® 5-alpha F' Iq Competent E. coli (High Efficiency) C2992I
C2992H
1-3x109 K12 tetracycline
NEB® 10-beta Competent E. coli (High Efficiency) C3019I
C3019H
1-3x109 K12 str
dam-/dcm- Competent E. coli C2925I
C2925H
1-3x106 K12 cam, nit, str
NEB® Stable Competent E. coli (High Efficiency) C3040I
C3040H
1-3 x 109 K12 tetracycline, streptomycin
Protein Expression Strains
NEB® Express Competent E. coli (High Efficiency) C2523I
C2523H
0.6-1x109 B nit
NEB® Express Iq Competent E. coli (High Efficiency) C3037I 0.6-1x109 B cam, nit
T7 Express Competent E. coli (High Efficiency) C2566I
C2566H
C2566AA
C2566A
0.6-1x109 B nit
T7 Express lysY Competent E. coli (High Efficiency) C3010I
C3010AA
C3010A
0.6-1x109 B cam, nit
T7 Express lysY/Iq Competent E. coli (High Efficiency) C3013I
C3013AA
C3013A
0.6-1x109 B cam, nit
T7 Express Crystal Competent E. coli (High Efficiency) C3022I 0.6-1x109 B nit
SHuffle® T7 Competent E. coli C3026J 1 x 106 K12 nit, spec, str
SHuffle® Express Competent E. coli C3028J 1 x 107 B nit, spec, str
SHuffle® T7 Express Competent E. coli C3029J 1 x 107 B nit, spec⁽⁷⁾, str
SHuffle® T7 Express lysY Competent E. coli C3030J 1 x 107 B cam, nit, spec⁽⁷⁾, str
BL21 Competent E. coli C2530H 1-5x107 B
BL21(DE3) Competent E. coli C2527I
C2527H
1-5x107 B
NiCo21(DE3) Competent E. coli C2529H 1-5x107 B
Lemo21(DE3) Competent E. coli C2528J 1-3x107 B cam
  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.
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