Guide to Host Strains

Highlights

• Superior for cloning vectors containing repeats and unstable fragments, such as lentiviral, retroviral and AAV vectors.
• Lacks ability to undergo homologous recombination due to the recA mutation.
• High transformation efficiency (> 1x10⁹ cfu/ug) and available for both chemical transformation and electroporation. Ideal for library cloning.
• Compatible with Gateway Cloning because it lacks the ccdAB operon.
• T1 phage resistant due to the fhuA mutation.
• Can produce high quality plasmid DNA due to the endA mutation (plasmids won’t be digested by endonuclease).
• Can be used for blue/white screening because it expresses the omega-fragment of the LacZ gene.

Genotype

F’[∆ccdAB proAB⁺ lacI^q lacZ∆M15 zzf::Tn10 (Tet^R)] recA1 endA1 fhuA mcrA ∆(mrr-hsdRMS-mcrBC) Φ80dlacZ∆M15 ∆(ara, leu)7697 araD139 ∆lacX74 galK16 galE15 e14^- relA1 nupG rpsL (Str^R) rph spoT1

Antibiotic resistance

Streptomycin, Tetracycline

Strain origin

E. coli K-12

Highlights

• Suitable for propagating plasmids that contain the ccdB gene.
• A recA-mutated line that is suitable for cloning DNA containing direct repeats, e.g. in lentiviral, retroviral, and AAV vectors.
• Compatible with the Gateway® system to propagate Gateway® destination, donor, and supercoiled entry vectors.
• An HB101 derivative that can be efficiently transformed with methylated DNA as well as unmethylated DNA such as PCR product and cDNA.

Genotype

F  λ^- gyrA462 araC14 leuB6 Δ(gpt-proA)62 lacY1 glnX44 galK2 recA13 rpsL20(Str^R) xylA5 mtl-1 thi-1 hsdS20(r_B^- m_B^-) Δ(mrr-hsdRMS-mcrBC)

Antibiotic resistance

Streptomycin

Strain origin

E. coli HB101 (a K-12 and E. coli B hybrid)

Highlights

• A versatile strain that is ideal for routine cloning.
• Efficient transformation with unmethylated DNA such as PCR product and cDNA.

Genotype

F  λ^- Δ(argF lac)169 Φ80dlacZΔM15 phoA glnV44 gyrA96 recA1 endA1 thi-1 hsdR17(r_K - m_K⁺)

Antibiotic resistance

None

Strain origin

E. coli K-12

Highlights

• Ideal for cloning large plasmids and BACs.
• Efficient transformation with methylated DNA as well as unmethylated DNA such as PCR product and cDNA.
• High competence due to its galE15 mutation.

Genotype

F  λ^- Δ(ara-leu)7697 araD139 ΔlacX74 duplication(514341-627601) galK16 galE15 e14^-(mcrmcrA^-) Φ80dlacZΔM15 recA1 relA1 endA1 Tn10.10 nupG rpsL(Str^R) rph spoT1 Δ(mrr-hsdRMS-mcrBC)

Antibiotic resistance

Streptomycin

Strain origin

E. coli K-12

Highlights

• A widely-used strain ideal for transformation and recombinant protein expression.
• Suitable for non-T7 expression due to its T7 RNA polymerase deficiency.
• Resistant to T1 phage due to the fhuA mutation.
• Protease deficient and exhibits low acetate production when grown on high glucose.
• Can be used with cold-shock induced vectors such as pCS for bacterial protein expression.

Genotype

F-  fhuA2 ompT gal dcm lon hsdS_B(r_B^- m_B^-) [malB⁺]_K-12(λ^S)

Antibiotic resistance

None

Strain origin

E. coli B

Highlights

• A widely-used E. coli strain ideal for transformation and recombinant protein expression.
• Contains the λDE3 lysogen, which carries a lacUV5 driven T7 RNA polymerase gene. T7 promoter driven genes require IPTG induction for maximum expression.
• Suitable for T7, T7-lac, or other E. coli promoters such as lac, tac, trc, and T5 as well as pET vectors.
• Protease deficient and exhibits low acetate production when grown on high glucose.

Genotype

F-  fhuA2 ompT gal dcm lon hsdS_B(r_B^- m_B^-)λ(DE3 [lacI lacUV5-T7p07 ind1 sam7 nin5]) [malB⁺]_K-12(λ^S)

Antibiotic resistance

None

Strain origin

E. coli B

Highlights

• Can be used to propagate plasmids containing direct repeats, e.g. lentiviral, retroviral, and AAV vectors.
• Capable of cloning and expressing “deleterious” genes.
• Accurate plasmid replication due to removal of mobile DNA elements, e.g. insertion (IS) elements.
• Resistant to T1 phage due to the fhuA mutation.
• Isolated plasmid DNA is free of Endonuclease I due to the removal of the i endA gene.

Genotype

MG1655 fhuACDB(del) endA(del) + deletion of 699 additional genes, including all IS elements and cryptic prophages

Antibiotic resistance

None

Strain origin

E. coli K-12

Highlights

• Can be used to propagate plasmids containing direct repeats, e.g. lentiviral, retroviral, and AAV vectors.
• Capable of cloning and expressing “deleterious” genes.
• Accurate plasmid replication due to removal of mobile DNA elements, e.g. insertion (IS) elements.
• Resistant to T1 phage due to the fhuA mutation.
• Isolated plasmid DNA is free of Endonuclease I due to the removal of the i endA gene.

Genotype

MG1655 ΔrecA fhuACDB(del) endA(del) + deletion of 699 additional genes, including all IS elements and cryptic prophages

Antibiotic resistance

None

Strain origin

E. coli K-12

Highlights

• A yeast strain used to express and recover recombinant proteins.
• High protein yields because of P. pastoris’s high biomass and efficient protein folding and secretion signals.
• Can be used with commercially available expression systems, e.g. pPP.
• Selection of Zeocin-resistant expression vector.

Genotype

wildtype

Antibiotic resistance

None

Strain origin

P. pastoris

Highlights

• A fast-growing diploid yeast strain used to express recombinant proteins.
• Commonly used with yeast expression vectors such as pYIP, pYCP, and pYEP.
• Capable of auxotrophic selection using histidine-, leucine-, tryptophan-, and uracil-deficient media.

Genotype

MATa his3Δ1 leu2 trp1-289 ura3-52/MATa his3Δ1 leu2 trp1-289 ura3-52

Antibiotic resistance

None

Strain origin

S. cerevisiae

Highlights

• Suitable for gene expression from arabinose-inducible araBAD due to TOP10 strain’s arabinose metabolism deficiency.
• Efficient transformation with unmethylated DNA such as PCR product and cDNA.
• Can be used for blue/white screening.
• Closely related to DH10B but is not protease deficient. These can be used for the same applications.

Genotype

F^- mcrA Δ(mrr-hsdRMS-mcrBC) Φ80lacZΔM15 ΔlacX74 recA1 araD139 Δ(ara, leu)7697 galU galK rpsL(Str^R) endA1 nupG

Antibiotic resistance

Streptomycin

Strain origin

E. coli K-12

Highlights

• A widely-used Agrobacterium strain used to efficiently transform various plant species, including Arabidopsis, tobacco, and Jatropha curcas.
• Can be used with T-DNA binary vectors for experiments in which custom DNA is inserted into the host genome.

Genotype

The A. tumefaciens genome contains four replicons: a circular chromosome (2.84 Mb, Rif^R), a linear chromosome (2.07 Mb), the pAT plasmid (0.54 Mb), and the disarmed Ti plasmid pAL4404 (Str^R).

Antibiotic resistance

Streptomycin, Rifampicin

Strain origin

A. tumefaciens Ach5