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 Construc-
tion(2)
Cloning/
Sub
Cloning
Blue/
White
Screening
laclq lysY endA¯(3) Protease
Deficient(4)
F' recA¯ T7 RNA Polymerase Cytoplasmic
disulfide
bond
formation(5)
Drug
Resistance(6)
Cloning Strains
dam-/dcm- Competent E. coli C2925I
C2925H
1-3x106 K12 cam, str, nit
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 tet
NEB® 10-beta Competent E. coli (High Efficiency) C3019I
C3019H
1-3x109 K12 str
NEB® Stable Competent E. coli (High Efficiency) C3040I
C3040H
1-3 x 109 K12 tet, str
Protein Expression Strains
NEBExpress® Competent E. coli (High Efficiency) C2523I
C2523H
0.6-1x109 B nit
BL21(DE3) Competent E. coli C2527I
C2527H
1-5x107 B
Lemo21(DE3) Competent E. coli C2528J 1-3x107 B cam
NiCo21(DE3) Competent E. coli C2529H 1-5x107 B
BL21 Competent E. coli C2530H 1-5x107 B
T7 Express Competent E. coli (High Efficiency) C2566I
C2566H
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
SHuffle® T7 Competent E. coli C3026J 1 x 106 K12 str, spec, nit
SHuffle® Express Competent E. coli C3028J 1 x 107 B spec(7), nit
SHuffle® T7 Express Competent E. coli C3029J 1 x 107 B spec(7), nit
SHuffle® T7 Express lysY Competent E. coli C3030J 1 x 107 B Cam, spec(7), nit
NEBExpress® Iq Competent E. coli (High Efficiency) C3037I 0.6-1x109 B cam, nit
  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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