E. coli Competent Cells Technical Bulletin

Literature # TB095

E. coli Competent Cells are prepared according to a modified procedure of Hanahan. The competent cells can be used for many standard molecular biology applications. JM109 competent cells are available for convenient transformation in two efficiencies: High Efficiency at greater than 10⁸cfu/µg and Subcloning Efficiency at greater than 10⁷cfu/µg. HB101 competent cells are available in high efficiency at greater than 10⁸cfu/µg. Pro 5-alpha competent cells are available in high efficiency at greater than 10⁹cfu/μg. JM109 and Pro 5-alpha cells are ideal hosts for many molecular biology applications. HB101 cells are useful for cloning in vectors that do not require α-complementation for blue/white screening. BL21(DE3)pLysS cells can be used with protein expression vectors that are under the control of the T7 promoter, such as pET vectors. This strain is lysogenic for lambda-DE3, which contains the T7 bacteriophage gene 1, encoding T7 RNA polymerase under the control of the lacUV5 promoter. BL21(DE3)pLysS also contains the pLysS plasmid, which carries the gene encoding T7 lysozyme. T7 lysozyme lowers the background expression level of target genes under the control of the T7 promoter but does not interfere with the level of expression achieved following induction with IPTG.