E.coli XL2-Blue MRF′ strain, competent cells

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Genotype andBackground

Δ(mcrA)183 Δ(mcrCB-hsdSMR-mrr)173 endA1supE44 thi-1 recA1 gyrA96 relA1 lac [F′ proAB lacIqZΔM15 Tn10 (Tetr) Amy Camr].

(Genes listed signify mutant alleles. Genes on the F′episome, however, are wild-type unless indicated otherwise.)

XL2-Blue MRF′ ultracompetent cells* are high-efficiencyderivatives of XL1-Blue MRF' supercompetent cells. Using ultracompetent celltechnology, it has achieved transformation efficiencies greater than 5 × 10 9 cfu/μg of pUC18DNA, making these cells an ideal choice for high-efficiency cloning. The XL-2Blue MRF' (Minus Restriction) strain is deficient in all known restrictionsystems (McrA-, McrCB-, McrF-, Mrr-, HsdR-), preventingcleavage of cloned DNA that carries cytosine and/or adenine methylation, whichis often present in eukaryotic DNA and cDNA. XL2-Blue MRF′ cells arerestriction-minus [Δ(mcrA)183, Δ(mcrCB-hsdSMR-mrr)173], and areendonuclease (endA), and recombination (recA) deficient. The lacIqZΔM15 gene on the F′episome allows blue-white screening for recombinant plasmids.

            Antibiotic Resistance

XL2-Blue MRF' cells are tetracycline and chloramphenicol resistant.