Bacterial Strain JM109 is a useful host for transformation of pGEM? Vectors and for production of single-stranded DNA from M13 or phagemid vectors. The strain grows well and is transformed efficiently by a variety of methods. Because JM109 is recA– and lacks the E. coli K restriction system, undesirable restriction of cloned DNA and recombination with host chromosomal DNA are prevented. The endonuclease A– mutation leads to an improved yield and quality of isolated plasmid DNA.

JM109 is deficient in β-galactosidase activity due to deletions in both genomic and episomal copies of the lacZ gene. The deletion in the episomal (F? factor) copy of the lacZ gene (lacZΔM15) can be complemented by addition of a functional α-peptide encoded by a pGEM?-Z or pGEM?-Zf Vector. If complementation does not occur, bacterial colonies are white. To maintain the F?, JM109 should be grown on minimal (M-9) media supplemented with 1mM thiamine.

Genotype: endA1, recA1, gyrA96, thi, hsdR17 (r_k^–, m_k⁺), relA1, supE44, Δ( lac-proAB), [F? traD36, proAB, laqI^qZΔM15].

Features - Benefits

• Reliable: Grows well and is transformed efficiently.
• Versatile: Useful for cloning, single-stranded DNA production, and blue/white screening.
• High Yields of Plasmid DNA: The endonuclease A– mutation improves yield and quality of isolated plasmid DNA.

Applications

• Blue/white color screening of pGEM?-Z and pGEM?-Zf(+/–) Vectors in the presence of X-Gal and IPTG.