Guide to Host Strains

VB UltraStable


  • 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.


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

Antibiotic Resistance

streptomycin, tetracycline

Strain Origin

E. coli K-12