Genotypes and genetic markers of E. coli competent cells

The genotype of an E. coli strain is an important aspect of competent cells in that it determines whether the cells can be grown on specific media, whether they may be used for transformation with specific DNA types, and whether they are appropriate for certain cloning strategies. Find the genotypes and the genetic markers described in the tables below for Invitrogen competent cells available from Thermo Fisher Scientific.

Genotypes of Invitrogen competent cells

 

Bacterial strainGenotype
BL21-AIF–ompT hsdSB (rB–, mB–) gal dcm araB::T7RNAP-tetA
BL21(DE3)F–ompT hsdSB (rB–, mB–) gal dcm (DE3)
BL21(DE3)pLysSF–ompT hsdSB (rB–, mB–) gal dcm (DE3) pLysS(CamR)
BL21(DE3)pLysE F–ompT hsdSB (rB–, mB–) gal dcm (DE3) pLysE(CamR)
BL21 Star(DE3) F–ompT hsdSB (rB–, mB–) gal dcm rne131 (DE3)
BL21 Star(DE3)pLysSF–ompT hsdSB (rB–, mB–) gal dcm rne131 (DE3) pLysS(CamR)
ccdB Survival 2F–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araΔ139 Δ(ara-leu)7697 galU galK rpsL(StrR) endA1 nupG fhuA::IS2
DH5αF– φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17(rK–, mK+) phoA supE44 λ–thi-1 gyrA96 relA1
DH5α-EF– φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17(rK–, mK+) gal–phoA supE44 λ–thi-1 gyrA96 relA1
DH5α-T1RF– φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17 (rK–, mK+) phoA supE44 λ–thi-1 gyrA96 relA1 tonA
DH5αF′IQF– φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17 (rK–, mK+) phoA supE44 λ–thi-1 gyrA96 relA1/F′ [proAB+lacIqZΔM15 zzf::Tn5(KmR)]
DH10BF–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara-leu)7697 galU galK λ–rpsL(StrR) nupG
DH10B T1RF–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara-leu)7697 galU galK λ–rpsL(StrR) nupG tonA
DH10Bac F–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara-leu)7697 galU galK λ–rpsL nupG / bMON14272 / pMON7124
DH12Sφ80ΔlacZΔM15 mcrA Δ(mrr-hsdRMS-mcrBC) araD139 Δ(ara-leu)7697 Δ(lacX74 galU galK rpsL(StrR) nupG recA1 / F′ [proAB+lacIqZΔM15 Tn10(TetR)]
INV110F′ [traD36 proAB lacIqlacZΔM15] rpsL (StrR) thr leu endA thi-1 lacY galK galT ara tonA tsx dam dcm supE44 Δ(lac-proAB) Δ(mcrC-mrr)102::Tn10(TetR)
INVαF′ F′ endA1 recA1 hsdR17 (rK–, mK+) supE44 thi-1 gyrA96 relA1 φ80lacZΔM15 Δ(lacZYA-argF)U169 λ–
Mach1 T1RF– φ80lacZΔM15 ΔlacX74 hsdR(rK–, mK+) ΔrecA1398 endA1 tonA
MC1061/P3F–hsdR(rK–, mK+) araD139 Δ(araABC-leu)7679 galU galK ΔlacX74 rpsL(StrR) thi mcrB / P3: KanR AmpR (am) TetR (am)
OmniMAX 2 T1RF′ [proAB+lacIqlacZΔM15 Tn10(TetR) Δ(ccdAB)] mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 Δ(lacZYA-argF)U169 endA1 recA1 supE44 thi-1 gyrA96 (NalR) relA1 tonA panD
PIR1F–∆lac169 rpoS(am) robA1 creC510 hsdR514 endA recA1 uidA(∆MluI)::pir-116
PIR2F–∆lac169 rpoS(am) robA1 creC510 hsdR514 endA recA1 uidA(∆MluI)::pir
Stbl2 F–mcrA Δ(mcrBC-hsdRMS-mrr) recA1 endA1 lon gyrA96 thi supE44 relA1 λ– Δ(lac-proAB)
Stbl3 F–mcrB mrr hsdS20(rB–, mB–) recA13 supE44 ara-14 galK2 lacY1 proA2 rpsL20(StrR) xyl-5 λ–leu mtl-1
Stbl4 mcrA Δ(mcrBC-hsdRMS-mrr) recA1 endA1 gyrA96 gal–thi-1 supE44 λ–relA1 Δ(lac-proAB) / F′ [proAB+lacIqZΔM15 Tn10(TetR)]
TOP10F–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araD139 Δ(ara-leu)7697 galU galK λ–rpsL(StrR) endA1 nupG
TOP10F′F′ [lacIq, Tn10(TetR)] mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araD139 Δ(ara-leu)7697 galU galK rpsL(StrR) endA1 nupG
TOP10/P3F–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araD139 Δ(ara-leu)7697galU galK rpsL(StrR) endA1 nupG λ– / P3: KanR AmpR (am) TetR (am)
Previously available strains

Previously available strains

 

StrainGenotypeAlternatives*
BL21-SIF– ompT lonhsdSB(rB–, mB–) gal dcm endA1 proUp::T7 RNAP::malQ-lacZTetSOther BL21 strains
ccdB Survival T1RF–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araΔ139 Δ(ara-leu)7697 galU galK rpsL(StrR) endA1 nupG tonA::Ptrc-ccdAccdB Survival 2 T1R
DB3.1F–gyrA462 endA1 Δ(sr1-recA) mcrB mrr hsdS20(rB–, mB–) supE44 ara-14 galK2 lacY1 proA2 rpsL20(StrR) xyl-5 λ–leu mtl1
DH11SmcrA Δ(mrr-hsd RMS-mcr BC) Δ(lac-proAB) Δ(recA1398) deoR[ZTS1] rpsL(StrR) srl–thi–supE / F′ [proAB+lacIqZΔM15]DH12S
DH5F–endA1 recA1 hsdR17(rK–, mK+) deoR thi-1 supE44 λ–gyrA96 relA1Other DH5α strains
DH5α-FTF–endA1 recA1 hsdR17(rK–, mK+) deoR thi-1 supE44 λ–gyrA96 relA1
DH5αFF′ φ80dlacZΔM15 Δ(lacZYA-argF)U169 endA1 recA1 hsdR17(rK–, mK+) deoR thi-1 phoA supE44 λ– gyrA96 relA1
DH5αMCRF–mcrA Δ(mrr-hsdRMS-mcrBC) φ80dlacZΔM15 Δ(lacZYA-argF)U169 endA1 recA1 deoR thi-1 phoA supE44 λ–gyrA96 relA1
DM1F–dam-13::Tn9(CamR) dcm mcrB hsdR–M+gal1 gal2 ara lac thr leu tonA tsxr Suo λ–
(also reported as ara dam dcm gal1 gal2 hsdR lac leu mcrB thr tonA tsx zac::Tn9(CamR))		INV110
HB101F–mcrB mrr hsdS20(rB–, mB–) recA13 supE44 ara14 galK2 lacY1 proA2 rpsL20(StrR) xyl5 λ–leu mtl1DH10B, TOP10, or Stbl3 (for lentiviral vectors)
LMG194F– ΔlacX74 galE thi rpsL(StrR) ΔphoA (PvuII) Δara714 leu::Tn10–
RR1 (recA+ version of HB101)F–mcrB mrr hsdS20(rB–, mB–) supE44 ara14 galK2 lacY1 proA2 rpsL20(StrR) xyl5 λ–leu mtl1–

*For recommendations for alternative strains, please check the competent cells selection guide, visit our Competent Cells Support Center, or contact our technical support team.

Keys to the genetic markers

 

Genetic markerDescription, phenotype, or benefit
(am)
  • Amber (UAG) mutation
  • See also supE and supF
AmpR
(also written ApR)
ara-14
araB
araC14
araD139		 (The hyphen in ara-14 indicates the exact locus is unknown.)
Δ(ara-leu)7697
  • Deletion of genes for biosynthesis of leucine from valine
  • Strain requires amino acid supplements to grow on synthetic minimal medium
argF
  • Mutation in the ornithine carbamoyltransferase gene
  • Blocks ability to make arginine
bMON14272
  • Parent bacmid (baculovirus shuttle vector) in DH10Bac
  • Harbors mini-F replicon, kanamycin resistance gene, attTn7 site, and lacZα complementation factor
CamR
(also written CmR)
  • Resistant to chloramphenicol
ccdA
ccdB
  • Encodes two genes from the F′ episome for control of cell death
  • Allows positive selection of colonies from successful cloning
(The ccdB protein causes gyrase-mediated DNA cleavage, while ccdA negates ccdB toxicity.)
creC510
(also called phoM)
  • Mutation of a gene involved in phosphate limitation
  • Expresses CreC constitutively
dam
  • Mutation in the DNA adenine methylase gene
  • Eliminates methylation of adenines at 5’ GATC 3’
  • Allows restriction with methylation sensitive enzymes
dcm
  • Mutation in the DNA cytosine methylase gene
  • Eliminates methylation of internal cytosines at 5’ CCWGG 3’
  • Allows restriction with methylation sensitive enzymes
(DE3)
  • λ lysogen that encodes T7 RNA polymerase
  • Induces expression in T7-driven expression systems
deoR
  • Mutation for constitutive expression of genes for deoxyribose synthesis
  • Involved in transport and catabolism of deoxyribonucleosides
  • Allows uptake of large plasmids
endA
  • Mutation in the nonspecific endonuclease I gene
  • Improves quality of isolated plasmid DNA
F–
  • Strain does not contain an F episome (also called fertility factor)
F+, F′, or Hfr
  • Strain contains an F episome (also called fertility factor)
  • Encodes strand-like structure called pili on the outer membrane of E. coli
  • May carry lacIq, lacZ∆M15, and an antibiotic resistance marker
  • Allows M13 phage infection
  • Enables ssDNA generation
(F+ usually designates a single-copy double-stranded circular extrachromosomal plasmid, F′ denotes harboring of additional genes on the F factor, and Hfr indicates chromosomal integration.)
fhuA
  • Mutation in the ferric hydroxamate uptake (also known as ferrichrome outer membrane transporter) gene
  • See tonA
galK
  • Mutation in the galactokinase gene
  • Blocks catabolism of galactose
  • Strain cannot grow using galactose as the sole carbon source
galU
  • Mutation in the glucose-1-phosphate uridylyltransferase gene
  • Blocks catabolism of galactose
  • Strain cannot grow using galactose as the sole carbon source
glnT
  • See supF
glnV
  • See supE
gyrA96
hflA150
  • Inactivation of a specific protease due to loss of function mutation
  • Results in high-frequency lysogeny by lambda (λ)
hsdRMS (The genetic marker may contain the allele number (e.g., hsdR17) and phenotype (e.g., (rK–, mK+), where r is for restriction, m for methylation, and the subscript K for the parental strain E. coli K12).)
IS2
  • Insertion element 2
KanR
(also called KmR)
λ–
  • Deletion of lambda (λ) lysogen
lacIq
  • Mutation in the lac repressor gene for constitutive expression
  • Inhibits transcription from the lac promoter, which can be overcome by IPTG addition
  • Allows controlled gene expression from promoters that carry the lac operator
(The superscript q indicates a constitutive mutation.)
lacY
  • Mutation in the galactoside permease gene
  • Blocks lactose utilization
∆lacX74
Δ(lacZYA-argF)U169
(also called ΔlacZU169)
  • Deletion of a chromosomal region including the lac operon and argF in the allele U169
  • Enhances resistance to hydrogen peroxide
lacZ′
  • 3′ deletion in lacZ
lacZ∆M15
leuB
  • Mutation in the β-isopropylmalate dehydrogenase gene
  • Strain requires leucine for growth on minimal medium
lon
  • Mutation in the lon (ATPase-dependent protease) gene
  • Reduces degradation of expressed recombinant proteins
mcrA
mcrBC
mrr
NalR
nupG
  • Mutation in a nucleoside transport gene
  • Increases plasmid uptake
ompT
  • Mutation in the ompT (outer membrane protease) gene
  • Reduces degradation of expressed recombinant proteins
φ80
  • Carries lambdoid prophage φ80
P3
  • 60 kb low-copy plasmid
  • Harbors ampicillin and tetracycline resistance genes with amber mutations
  • Allows selection of supF-containing plasmids
  • Confers kanamycin resistance
phoA
pir
pLys
pMON7124
  • pBR322-derived helper plasmid in DH10Bac
  • Carries transposase genes for insertion of the donor plasmid mini-Tn7 into the parent bacmid bMON14272
proAB
  • Mutation in proline metabolism genes A and B
  • Strain requires proline for growth on minimal medium
Ptrc-ccdA
  • ccdA transcription driven by the trc promoter
  • Allows propagation of ccdB-containing plasmids
recA1
recA13
  • Mutations in genes for general recombination of DNA
  • Enables cloning of unstable DNA, e.g., sequences with repeats
relA
  • Mutation in a regulatory gene for coupling between transcription and translation
  • Allows RNA synthesis in limiting amino acid concentrations or in the absence of protein synthesis (i.e., relaxed phenotype)
RNAP
rne131
  • Mutation in the RNase E gene
  • Helps prevent mRNA degradation
robA1
  • Mutation in the right oriC-binding protein gene
rpoS
  • Mutation in the RNA polymerase sigma factor gene
  • Abolishes expression of some stress-induced proteases
  • Improves yield of certain recombinant proteins at high temperature
rpsL
  • Mutation in the 30S ribosomal protein small subunit S12 gene
  • Confers resistance to streptomycin (which targets the 30S subunit)
StrR
(also written SmR)
supE
(also called glnV)
  • Suppresses the amber (UAG) mutation
  • Suppressor tRNA inserts glutamine at the mutation site
  • Required for growth of strains with amber mutations and phage display systems
supF
(also called tyrT)
  • Suppresses the amber (UAG) mutation
  • Suppressor tRNA inserts tyrosine at the mutation site
  • Required for growth of strains with amber mutations and phage display systems
TetR
(also written TcR)
Tets
(also written TcS)
thi-1
  • Mutation in a thiamine metabolism gene
  • Strain requires thiamine for growth on minimal medium
(The hyphen in thi-1 indicates the exact locus is unknown.)
thr
  • Mutation in a threonine metabolism gene
  • Strain requires threonine for growth on minimal medium
Tn5 (KmR)
  • Transposon that confers resistance to kanamycin
Tn9 (CamR)
Tn10 (TetR)
tonA
(also called fhuA)
  • Mutation in an outer membrane iron uptake receptor gene
  • Confers resistance to the lytic bacteriophage T1, T5, and φ80
traD36  
  • Mutation in a transfer factor gene
  • Prevents transfer of F′ episome
tsx
  • Confers resistance to phage T6 and the polypeptide bacteriocin colicin K
uidA(∆MluI)
  • Mutation in the β-glucuronidase gene between MluI restriction sites
xyl-5
  • Mutation in a xylose metabolism gene
  • Blocks xylose utilization
zac
  • Transposon insertion at the chromosomal map position 2-3 min
zzf::Tn5
  • Insertion (::) of Tn5 on the F plasmid
(zzf denotes an insertion mutation on the F′ episome.)
Competent cell genotypes

Genotypes of Invitrogen competent cells

 

Bacterial strainGenotype
BL21-AIF–ompT hsdSB (rB–, mB–) gal dcm araB::T7RNAP-tetA
BL21(DE3)F–ompT hsdSB (rB–, mB–) gal dcm (DE3)
BL21(DE3)pLysSF–ompT hsdSB (rB–, mB–) gal dcm (DE3) pLysS(CamR)
BL21(DE3)pLysE F–ompT hsdSB (rB–, mB–) gal dcm (DE3) pLysE(CamR)
BL21 Star(DE3) F–ompT hsdSB (rB–, mB–) gal dcm rne131 (DE3)
BL21 Star(DE3)pLysSF–ompT hsdSB (rB–, mB–) gal dcm rne131 (DE3) pLysS(CamR)
ccdB Survival 2F–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araΔ139 Δ(ara-leu)7697 galU galK rpsL(StrR) endA1 nupG fhuA::IS2
DH5αF– φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17(rK–, mK+) phoA supE44 λ–thi-1 gyrA96 relA1
DH5α-EF– φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17(rK–, mK+) gal–phoA supE44 λ–thi-1 gyrA96 relA1
DH5α-T1RF– φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17 (rK–, mK+) phoA supE44 λ–thi-1 gyrA96 relA1 tonA
DH5αF′IQF– φ80lacZΔM15 Δ(lacZYA-argF)U169 recA1 endA1 hsdR17 (rK–, mK+) phoA supE44 λ–thi-1 gyrA96 relA1/F′ [proAB+lacIqZΔM15 zzf::Tn5(KmR)]
DH10BF–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara-leu)7697 galU galK λ–rpsL(StrR) nupG
DH10B T1RF–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara-leu)7697 galU galK λ–rpsL(StrR) nupG tonA
DH10Bac F–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 endA1 araD139 Δ(ara-leu)7697 galU galK λ–rpsL nupG / bMON14272 / pMON7124
DH12Sφ80ΔlacZΔM15 mcrA Δ(mrr-hsdRMS-mcrBC) araD139 Δ(ara-leu)7697 Δ(lacX74 galU galK rpsL(StrR) nupG recA1 / F′ [proAB+lacIqZΔM15 Tn10(TetR)]
INV110F′ [traD36 proAB lacIqlacZΔM15] rpsL (StrR) thr leu endA thi-1 lacY galK galT ara tonA tsx dam dcm supE44 Δ(lac-proAB) Δ(mcrC-mrr)102::Tn10(TetR)
INVαF′ F′ endA1 recA1 hsdR17 (rK–, mK+) supE44 thi-1 gyrA96 relA1 φ80lacZΔM15 Δ(lacZYA-argF)U169 λ–
Mach1 T1RF– φ80lacZΔM15 ΔlacX74 hsdR(rK–, mK+) ΔrecA1398 endA1 tonA
MC1061/P3F–hsdR(rK–, mK+) araD139 Δ(araABC-leu)7679 galU galK ΔlacX74 rpsL(StrR) thi mcrB / P3: KanR AmpR (am) TetR (am)
OmniMAX 2 T1RF′ [proAB+lacIqlacZΔM15 Tn10(TetR) Δ(ccdAB)] mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 Δ(lacZYA-argF)U169 endA1 recA1 supE44 thi-1 gyrA96 (NalR) relA1 tonA panD
PIR1F–∆lac169 rpoS(am) robA1 creC510 hsdR514 endA recA1 uidA(∆MluI)::pir-116
PIR2F–∆lac169 rpoS(am) robA1 creC510 hsdR514 endA recA1 uidA(∆MluI)::pir
Stbl2 F–mcrA Δ(mcrBC-hsdRMS-mrr) recA1 endA1 lon gyrA96 thi supE44 relA1 λ– Δ(lac-proAB)
Stbl3 F–mcrB mrr hsdS20(rB–, mB–) recA13 supE44 ara-14 galK2 lacY1 proA2 rpsL20(StrR) xyl-5 λ–leu mtl-1
Stbl4 mcrA Δ(mcrBC-hsdRMS-mrr) recA1 endA1 gyrA96 gal–thi-1 supE44 λ–relA1 Δ(lac-proAB) / F′ [proAB+lacIqZΔM15 Tn10(TetR)]
TOP10F–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araD139 Δ(ara-leu)7697 galU galK λ–rpsL(StrR) endA1 nupG
TOP10F′F′ [lacIq, Tn10(TetR)] mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araD139 Δ(ara-leu)7697 galU galK rpsL(StrR) endA1 nupG
TOP10/P3F–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araD139 Δ(ara-leu)7697galU galK rpsL(StrR) endA1 nupG λ– / P3: KanR AmpR (am) TetR (am)
Previously available strains

Previously available strains

 

StrainGenotypeAlternatives*
BL21-SIF– ompT lonhsdSB(rB–, mB–) gal dcm endA1 proUp::T7 RNAP::malQ-lacZTetSOther BL21 strains
ccdB Survival T1RF–mcrA Δ(mrr-hsdRMS-mcrBC) φ80lacZΔM15 ΔlacX74 recA1 araΔ139 Δ(ara-leu)7697 galU galK rpsL(StrR) endA1 nupG tonA::Ptrc-ccdAccdB Survival 2 T1R
DB3.1F–gyrA462 endA1 Δ(sr1-recA) mcrB mrr hsdS20(rB–, mB–) supE44 ara-14 galK2 lacY1 proA2 rpsL20(StrR) xyl-5 λ–leu mtl1
DH11SmcrA Δ(mrr-hsd RMS-mcr BC) Δ(lac-proAB) Δ(recA1398) deoR[ZTS1] rpsL(StrR) srl–thi–supE / F′ [proAB+lacIqZΔM15]DH12S
DH5F–endA1 recA1 hsdR17(rK–, mK+) deoR thi-1 supE44 λ–gyrA96 relA1Other DH5α strains
DH5α-FTF–endA1 recA1 hsdR17(rK–, mK+) deoR thi-1 supE44 λ–gyrA96 relA1
DH5αFF′ φ80dlacZΔM15 Δ(lacZYA-argF)U169 endA1 recA1 hsdR17(rK–, mK+) deoR thi-1 phoA supE44 λ– gyrA96 relA1
DH5αMCRF–mcrA Δ(mrr-hsdRMS-mcrBC) φ80dlacZΔM15 Δ(lacZYA-argF)U169 endA1 recA1 deoR thi-1 phoA supE44 λ–gyrA96 relA1
DM1F–dam-13::Tn9(CamR) dcm mcrB hsdR–M+gal1 gal2 ara lac thr leu tonA tsxr Suo λ–
(also reported as ara dam dcm gal1 gal2 hsdR lac leu mcrB thr tonA tsx zac::Tn9(CamR))		INV110
HB101F–mcrB mrr hsdS20(rB–, mB–) recA13 supE44 ara14 galK2 lacY1 proA2 rpsL20(StrR) xyl5 λ–leu mtl1DH10B, TOP10, or Stbl3 (for lentiviral vectors)
LMG194F– ΔlacX74 galE thi rpsL(StrR) ΔphoA (PvuII) Δara714 leu::Tn10–
RR1 (recA+ version of HB101)F–mcrB mrr hsdS20(rB–, mB–) supE44 ara14 galK2 lacY1 proA2 rpsL20(StrR) xyl5 λ–leu mtl1–

*For recommendations for alternative strains, please check the competent cells selection guide, visit our Competent Cells Support Center, or contact our technical support team.

Keys to genetic markers

Keys to the genetic markers

 

Genetic markerDescription, phenotype, or benefit
(am)
  • Amber (UAG) mutation
  • See also supE and supF
AmpR
(also written ApR)
ara-14
araB
araC14
araD139		 (The hyphen in ara-14 indicates the exact locus is unknown.)
Δ(ara-leu)7697
  • Deletion of genes for biosynthesis of leucine from valine
  • Strain requires amino acid supplements to grow on synthetic minimal medium
argF
  • Mutation in the ornithine carbamoyltransferase gene
  • Blocks ability to make arginine
bMON14272
  • Parent bacmid (baculovirus shuttle vector) in DH10Bac
  • Harbors mini-F replicon, kanamycin resistance gene, attTn7 site, and lacZα complementation factor
CamR
(also written CmR)
  • Resistant to chloramphenicol
ccdA
ccdB
  • Encodes two genes from the F′ episome for control of cell death
  • Allows positive selection of colonies from successful cloning
(The ccdB protein causes gyrase-mediated DNA cleavage, while ccdA negates ccdB toxicity.)
creC510
(also called phoM)
  • Mutation of a gene involved in phosphate limitation
  • Expresses CreC constitutively
dam
  • Mutation in the DNA adenine methylase gene
  • Eliminates methylation of adenines at 5’ GATC 3’
  • Allows restriction with methylation sensitive enzymes
dcm
  • Mutation in the DNA cytosine methylase gene
  • Eliminates methylation of internal cytosines at 5’ CCWGG 3’
  • Allows restriction with methylation sensitive enzymes
(DE3)
  • λ lysogen that encodes T7 RNA polymerase
  • Induces expression in T7-driven expression systems
deoR
  • Mutation for constitutive expression of genes for deoxyribose synthesis
  • Involved in transport and catabolism of deoxyribonucleosides
  • Allows uptake of large plasmids
endA
  • Mutation in the nonspecific endonuclease I gene
  • Improves quality of isolated plasmid DNA
F–
  • Strain does not contain an F episome (also called fertility factor)
F+, F′, or Hfr
  • Strain contains an F episome (also called fertility factor)
  • Encodes strand-like structure called pili on the outer membrane of E. coli
  • May carry lacIq, lacZ∆M15, and an antibiotic resistance marker
  • Allows M13 phage infection
  • Enables ssDNA generation
(F+ usually designates a single-copy double-stranded circular extrachromosomal plasmid, F′ denotes harboring of additional genes on the F factor, and Hfr indicates chromosomal integration.)
fhuA
  • Mutation in the ferric hydroxamate uptake (also known as ferrichrome outer membrane transporter) gene
  • See tonA
galK
  • Mutation in the galactokinase gene
  • Blocks catabolism of galactose
  • Strain cannot grow using galactose as the sole carbon source
galU
  • Mutation in the glucose-1-phosphate uridylyltransferase gene
  • Blocks catabolism of galactose
  • Strain cannot grow using galactose as the sole carbon source
glnT
  • See supF
glnV
  • See supE
gyrA96
hflA150
  • Inactivation of a specific protease due to loss of function mutation
  • Results in high-frequency lysogeny by lambda (λ)
hsdRMS (The genetic marker may contain the allele number (e.g., hsdR17) and phenotype (e.g., (rK–, mK+), where r is for restriction, m for methylation, and the subscript K for the parental strain E. coli K12).)
IS2
  • Insertion element 2
KanR
(also called KmR)
λ–
  • Deletion of lambda (λ) lysogen
lacIq
  • Mutation in the lac repressor gene for constitutive expression
  • Inhibits transcription from the lac promoter, which can be overcome by IPTG addition
  • Allows controlled gene expression from promoters that carry the lac operator
(The superscript q indicates a constitutive mutation.)
lacY
  • Mutation in the galactoside permease gene
  • Blocks lactose utilization
∆lacX74
Δ(lacZYA-argF)U169
(also called ΔlacZU169)
  • Deletion of a chromosomal region including the lac operon and argF in the allele U169
  • Enhances resistance to hydrogen peroxide
lacZ′
  • 3′ deletion in lacZ
lacZ∆M15
leuB
  • Mutation in the β-isopropylmalate dehydrogenase gene
  • Strain requires leucine for growth on minimal medium
lon
  • Mutation in the lon (ATPase-dependent protease) gene
  • Reduces degradation of expressed recombinant proteins
mcrA
mcrBC
mrr
NalR
nupG
  • Mutation in a nucleoside transport gene
  • Increases plasmid uptake
ompT
  • Mutation in the ompT (outer membrane protease) gene
  • Reduces degradation of expressed recombinant proteins
φ80
  • Carries lambdoid prophage φ80
P3
  • 60 kb low-copy plasmid
  • Harbors ampicillin and tetracycline resistance genes with amber mutations
  • Allows selection of supF-containing plasmids
  • Confers kanamycin resistance
phoA
pir
pLys
pMON7124
  • pBR322-derived helper plasmid in DH10Bac
  • Carries transposase genes for insertion of the donor plasmid mini-Tn7 into the parent bacmid bMON14272
proAB
  • Mutation in proline metabolism genes A and B
  • Strain requires proline for growth on minimal medium
Ptrc-ccdA
  • ccdA transcription driven by the trc promoter
  • Allows propagation of ccdB-containing plasmids
recA1
recA13
  • Mutations in genes for general recombination of DNA
  • Enables cloning of unstable DNA, e.g., sequences with repeats
relA
  • Mutation in a regulatory gene for coupling between transcription and translation
  • Allows RNA synthesis in limiting amino acid concentrations or in the absence of protein synthesis (i.e., relaxed phenotype)
RNAP
rne131
  • Mutation in the RNase E gene
  • Helps prevent mRNA degradation
robA1
  • Mutation in the right oriC-binding protein gene
rpoS
  • Mutation in the RNA polymerase sigma factor gene
  • Abolishes expression of some stress-induced proteases
  • Improves yield of certain recombinant proteins at high temperature
rpsL
  • Mutation in the 30S ribosomal protein small subunit S12 gene
  • Confers resistance to streptomycin (which targets the 30S subunit)
StrR
(also written SmR)
supE
(also called glnV)
  • Suppresses the amber (UAG) mutation
  • Suppressor tRNA inserts glutamine at the mutation site
  • Required for growth of strains with amber mutations and phage display systems
supF
(also called tyrT)
  • Suppresses the amber (UAG) mutation
  • Suppressor tRNA inserts tyrosine at the mutation site
  • Required for growth of strains with amber mutations and phage display systems
TetR
(also written TcR)
Tets
(also written TcS)
thi-1
  • Mutation in a thiamine metabolism gene
  • Strain requires thiamine for growth on minimal medium
(The hyphen in thi-1 indicates the exact locus is unknown.)
thr
  • Mutation in a threonine metabolism gene
  • Strain requires threonine for growth on minimal medium
Tn5 (KmR)
  • Transposon that confers resistance to kanamycin
Tn9 (CamR)
Tn10 (TetR)
tonA
(also called fhuA)
  • Mutation in an outer membrane iron uptake receptor gene
  • Confers resistance to the lytic bacteriophage T1, T5, and φ80
traD36  
  • Mutation in a transfer factor gene
  • Prevents transfer of F′ episome
tsx
  • Confers resistance to phage T6 and the polypeptide bacteriocin colicin K
uidA(∆MluI)
  • Mutation in the β-glucuronidase gene between MluI restriction sites
xyl-5
  • Mutation in a xylose metabolism gene
  • Blocks xylose utilization
zac
  • Transposon insertion at the chromosomal map position 2-3 min
zzf::Tn5
  • Insertion (::) of Tn5 on the F plasmid
(zzf denotes an insertion mutation on the F′ episome.)

References

  1. Casali N (2003) Escherichia coli Host Strains. In: Casali N, Preston A (editor), E. coli Plasmid Vectors: Methods and Applications. Totowa: Humana Press, pp 27–48.
  2. Raleigh EA, Elbing K, Brent R (2002) Selected Topics from Classical Bacterial Genetics, In: Ausubel FM, Brent R, Kingston RE et al. (editors), Current Protocols in Molecular Biology. Brooklyn: Wiley, Unit 1.4.
  3. Maloy SR, Hughes KT (2007) Strain Collections and Genetic Nomenclature. In: Methods in Enzymology. San Diego: Academic Press, 421:3–8.
  4. E. coli Genetic Resources at Yale CGSC
  5. Berlyn MK (1998) Linkage map of Escherichia coli K-12, edition 10: the traditional map. Microbiol Mol Biol Rev 62(3):814–984.
  6. Schaechter M et al. (2001) Escherichia coli and Salmonella 2000: the view from here. Microbiol MolBiol Rev 65(1):119–130.

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