Hello Messaoudi Djamel

For amplifying a lentiviral plasmid containing an active ccdB gene, you may use a specialized E. coli strain, DB3.1 or One Shot ccdB Survival, that is resistant to the ccdB protein's toxicity.

The DB3.1 strain carries a specific mutation (gyrA462) in its DNA gyrase gene, which is the target of the ccdB toxin. This mutation makes the gyrase resistant to ccdB and allows the bacteria to grow and propagate plasmids containing the toxic gene.

The One Shot ccdB Survival is a commercially available strain from Thermo Fisher Scientific that is also resistant to ccdB toxicity. It is functionally like DB3.1 for propagating plasmids with an active ccdB gene.

The details are provided in the link below.

https://www.thermofisher.com/order/catalog/product/A10460

Best,

Alternatively, any E. coli strain that carries the F' episome will also confer ccdB survival since the F' carries the ccd operon and expresses the antitoxin. Examples of such strains are JM109 or JM110, NEB Stable, XL1-Blue, XL10-Gold and a variety of others. They will be marked as F' (and not as F-) in a typical genotype.

Malcolm Nobre Thank you for your answer. However, both strains are not recommended for amplifying unstable DNA such as lentiviral plasmids. That’s why I’m wondering if there is a strain that combines both characteristics (ccdB resistance and suitability for amplifying unstable DNA).

Michael J. Benedik Thank you for your answer. I'm using NEB stable as receiving bacteria for cloning. so with NEB Stable, I obtained rather mixed results. When I transform NEB Stable with the Ltv plasmid carrying ccdB, I get many false positives (even in bacteria transformed with the undigested plasmid), although they are F– and therefore should not be resistant to ccdB. This was confirmed when I transformed them with a standard (non-lentiviral) plasmid carrying ccdB, where I obtained almost no colonies. I also re-sequenced my LTV-ccdB plasmid, and it does contain the ccdB cassette derived from the non-lentiviral plasmid. So I'm a bit confused about it

NEB Stable is an F' strain so it should be resistant to ccdB. Be careful, there are a number of different STBL strains out there, I think STBL2 and STBL3 are F- but NEB Stable carries an F'.