Competent Cells for Cloning Unstable DNA

A gloved hand holding a petri dish containing blue and white bacterial colonies

Plasmids containing repetitive DNA sequences, such as those derived from retroviruses and lentiviruses, are susceptible to loss of integrity due to recombination events. In addition, GC- or AT- rich sequences (>70%) and sequences prone to the formation of secondary structures are notoriously difficult to clone. When cloning unstable DNA, choose a competent cell strain designed for the task. Bacteria with defective recombinases are more likely to faithfully replicate plasmids bearing unstable DNA inserts.

Use Stbl competent cells to avoid DNA recombination while cloning

Stbl competent cells express mutated forms of the RecA protein, rendering them recombination defective. Additional variations in genotype contribute to the ability of these strains to maintain plasmid integrity during cloning and replication. Notably, the Stbl3 strain demonstrated an exceptional maintenance of stability of an instability-prone lentiviral vector plasmid [1] and is the strain used in the seminal CRISPR-Cas9 protocol [2].

Learn more about propagating unstable DNA constructs

Compare Stbl competent cells for cloning unstable DNA

Three strains of Invitrogen Stbl competent cells are available, and each has properties that impact its performance with plasmids of various size and origin.

Product
Product	MAX Efficiency Stbl2 Chemically Competent Cells	Stbl3 Chemically Competent E. coli	ElectroMAX Stbl4 Competent Cells
Recommended for	Cloning direct repeat retroviral sequences and tandem array genes	Cloning direct repeats found in lentiviral expression vectors	Generating complex cDNA and genomic libraries
Derived from strain	E. coli JM109/J5	E. coli HB101	Stbl2/E. coli JM109/J5
Transformation efficiency	>1 x 10⁹ cfu/µg	>1 x 10⁸cfu/µg	>5 x 10⁹ cfu/µg
Type of transformation	Chemical/Heat shock	Chemical/Heat shock	Electroporation
Compatible plasmid size	>20 kb	>20 kb	>100 kb
Blue/white screening	–	–
Contains F´ episome for making single-stranded DNA	–	–
Available format(s)	5 x 200 µL/tube	21 x 50 µL/tube 1 x 96-well plate with 20 µL/well 1 x 96-tube rack with 50 µL/tube	5 x 100 µL/tube

Still not sure which Stbl competent cells are right for your experiment?

Compare genotypes of Stbl strains
Shop all Invitrogen Stbl competent cells

References

Competent cells: Featured products

In addition to competent cells, we offer a broad suite of products for the cloning workflow.

Magnified image of purple, rod-shaped bacteria

Microbial
media

Explore types of bacterial growth media to use for cloning, plasmid DNA preparation, and protein expression.

Browse media

Electroporation
cuvettes

Learn more about universal-fit electroporation cuvettes for use with competent cells.

View electroporation cuvettes

Photo of TOPO PCR cloning kit product box and content

TOPO PCR
cloning kits

Learn more about one-step PCR cloning that combines traditional restriction and ligation cloning.

View TOPO kits

Gibson Assembly
cloning kits

Gibson Assembly cloning kits provide highly efficient, seamless cloning, enabling the assembly of multiple DNA fragments of varying lengths into any vector.

Explore Gibson Assembly cloning

Resources

Have any questions on competent cells or transformation? Click on the resources listed below to access overviews, videos, genotype guides, and educational resources.