CopyCutter EPI400 E. coli cells reduce the copy number of many common plasmid vectors (including pUC, pBR, and pET) by 25-fold, allowing “toxic” genes or unstable DNA sequences to be more easily cloned. As seen in the accompanying figure, the highly toxic regB gene was successfully cloned into a pET11 vector only when recombinants were transformed into CopyCutter cells. The cells offer high efficiency (>1 × 10⁹ cfu/μg of pUC19), recA, endA, and mcrA deficient, and compatible with blue/white color screening. If increased DNA yields are desired during purification, the copy number of the plasmid can be increased using CopyCutter Induction Solution.