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
1-3x109 K12 nit
NEB® 5-alpha Competent E. coli (High Efficiency) C2987U
1-3x109 K12 none
NEB® 5-alpha F' Iq Competent E. coli (High Efficiency) C2992I
1-3x109 K12 tetracycline
NEB® 10-beta Competent E. coli (High Efficiency) C3019I
1-3x109 K12 str
dam-/dcm- Competent E. coli C2925I
1-3x106 K12 cam, nit, str
NEB® Stable Competent E. coli (High Efficiency) C3040I
1-3 x 109 K12 tetracycline, streptomycin
Protein Expression Strains
NEB® Express Competent E. coli (High Efficiency) C2523I
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
0.6-1x109 B nit
T7 Express lysY Competent E. coli (High Efficiency) C3010I
0.6-1x109 B cam, nit
T7 Express lysY/Iq Competent E. coli (High Efficiency) C3013I
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
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.
Loading Spinner