One Shot Stbl3 Chemically Competent E. coli are designed for cloning direct repeats found in lentiviral expression vectors as these cells reduce the frequency of homologous recombination of direct repeats found in lentiviral vectors (ViraPower Lentiviral Expression kits) and other retroviral vectors (instability-prone HIV-based plasmids). The Stbl3 strain has been essential for many applications, including genome editing CRISPR workflows, vaccine development (including SARS-CoV-2 vaccine research), cloning, and maintaining vectors with multiple repeats (e.g., gene coding protein with repeated sequence). The transformation efficiency of One Shot Stbl3 chemically competent cells is >1 x 10⁸ cfu/μg plasmid DNA.

The Stbl3 strain is derived from the HB101 E. coli strain with a hybrid K-12 and B strain genome. It contains the recA13 allele of the recA mutation that reduces nonspecific recombination occurrence in cloned DNA. Mutations in the Stbl3 methylation-dependent restriction system (mcrB, mrr, and hsdS20) allow construction of cloning genomic DNA. This strain has endA1+, a nonspecific endonuclease I that digests DNA. The Stbl3 strain also reproducibly yields more plasmid DNA than DH strains (10-fold or more plamsmid DNA than the TOP10 strain) and sustainably produces high titer lentivirus.

One Shot Stbl3 Chemically Competent E. coli offer:
• Expected efficiency of >1 x 10⁸ transformants/μg plasmid DNA
• Optimal performance for the propagation of lentiviral vectors and maintenance of direct repeats
• Enhanced genomic DNA cloning capacity (mcrB, mrr, and hsdS20)
• Capable of producing high DNA yields 

Note: For optimal performance and to maintain plasmid with complex repeat sequences, Stbl3 cells should be cultured at 30°C. When performing plasmid DNA isolation from Stbl3 cells that have wild type endonuclease I (endA1+), ensure that buffers contain 10 mM EDTA. EDTA will inactivate the endonuclease and avoid DNA nicking and vector degradation (follow plasmid DNA purification kit instructions for endA1+ E. coli strains).

Easy-to-use One Shot format
Stbl3 Chemically Competent E. coli cells are supplied in the convenient, single-reaction One Shot format. The single-tube, single-use format allows all steps of the transformation protocol, up to plating, to take place in the same tube, thereby helping save time and prevent contamination.

Genotype
F^–mcrB mrr hsdS20(r_B–, m_B–) recA13 supE44 ara-14 galK2 lacY1 proA2 rpsL20(StrR) xyl-5 λ–leu mtl-1

Find the strain and format that fit your needs
Other Stbl strains are available with different genetic background.
The Stbl3 strain is available in MultiShot format for high throughput applications.
Explore bacterial growth media formats