|Genotype||∆(araA-leu)7697 [araD139]B/r ∆(codB-lacI)3 = ∆lac74 galK16 galE15 e14- mcrA0 relA1 rpsL150 spoT1 mcrB1 hsdR2 λ+|
|Phenotype||Streptomycin resistant, zeocin resistant|
Useful host for primary transformation. Transforms very well by the CaCl2 method (107/µg). There is no Type I restriction; incoming DNA receives the E. coli K modification.
Lysogenized with λ wild type.
Recommended as maintenance host for plasmids containing the PL or PR promoter from phage λ.
It is recommended to grow MC1061(λ), containing pPL plasmids, at 28°C.
As this strain is deleted for the lacI repressor gene, it is not a suitable host for plasmids carrying the lac promoter or derivatives thereof, such as tac, trc, N25/O2 … promoters. In the absence of repression, continuous transcription from the lac promoter is likely to result in plasmid instability.
The zeocin resistance is most probably related to the presence of a functional recA gene (recA+).