Strains for cloning:

The strains for cloning are recombination deficient.

DH5-a
F–, ø80dlacZΔM15, Δ(lacZYA-argF)U169, deoR, recA1, endA1, hsdR17(rK –, mK+), phoA, supE44, λ–, thi-1, gyrA96, relA1

XL-1(blue)
recA1, endA1, gyrA96, thi-1, hsdR17(r K-,mK +), supE44, relA1,l-, [F' proAB, lacIq Z ΔM15, Tn10(Tetr )].

GM2163
F-dam-13::Tn 9 dcm-6 hsdR2 leuB6 his-4 thi-1 ara-14 lacY1 galK2 galT22 xyl-5 mtl-1 rpsL136 tonA31 tsx-78 supE44McrA - McrB-
This strain lacks dam methylation. Isolate plasmids from this strain to have them without dam methylation, e. g. for XbaI sites


KC8
hsdR leuB600 trpC9830 pyr::Tn5 hisB463 lacDeltaX74 strA galU galK
E. coli KC8 carries the trpC, leuB, and hisB mutations for complementation to yeast TRP1, LEU2, and HIS3 wild-type genes, respectively.

M15
 NaI[s] Str[s] Rif[s] Thi[-] lac[-] Ara[+] Gal[+] Mtl[-] F[-] RecA[+] Uvr[+] Lon[+]

SG13009
NaI[s] Str[s] Rif[s] Thi[-] lac[-] Ara[+] Gal[+] Mtl[-] F[-] RecA[+] Uvr[+] Lon[+]

TG1
F’traD36 lacIqΔ(lacZ)M15 proA+B+ /supE Δ(hsdM-mcrB)5 (rk - mk - McrB-) thi Δ(lac-proAB)


Strains for protein expression:

Do not keep these strains for longer than one week, since the host cells recombine the plasmids. Clones containing expression plasmids tend to lose the protein expression despite maintaining the AmpR. Always use freshly transformed clones (not older than one week).

BL21(DE)
E. coli B, F- , dcm, ompT, hsdS(rB -mB -), gal l(DE3).
This strain has to be employed for vectors with a T7 promoter e. g. pET vectors. Contains the T7 RNA polymerase gene under control of the lacUV5 promoter. The polymerase gene is integrated into the bacterial chromosome from l(DE3). Induce expression with IPTG. Use for non-toxic protein expression (Stratagene).

BL21 Star (DE3)
E. coli B / r, - ompT hsdSB (rB-mB-) gal dcm rne131 (DE3) This strain is useful for expression of heterologous non-toxic proteins. Derived from BL21 (DE3) with all previous mentioned properties. Contains the additional rne131 gene mutation, which encodes a RNase E that lacks the ability to degrade mRNA, while maintaining rRNA maturation ability. This results in an allover higher mRNA stability thus facilitating a higher level of protein translation.

BL21 rosetta2
F- opmT hsdSB(rB-mB-) gal dcm pRARE2(CamR)
contains a CamR plasmid that encodes rare tRNAs for following codons: AUA, AGG AGA, CUA, CCC, GGA, CGG

BL21 codon plus (Stratagene)
The genotype is not completely clear, e. g. DE3??. The cells contain a CamR plasmid that encodes tRNAs for two rare codons (Arg, Pro). TetR has not been tested!
E. coli B, F-ompT hsdS(rB mB) dcm+ TetR gal lambda endA Hte [argU proL CamR]