The Inoue Method for Preparation and Transformation of Competent Escherichia coli: “Ultracompetent” Cells

This protocol differs from other transformation procedures in that the bacterial culture is grown at 18°C rather than the conventional 37°C. Otherwise, the protocol is unremarkable and follows a fairly standard course. Under standard laboratory conditions, efficiencies of 1 × 10 8 to 3 × 10 8 transformed colonies/µg of plasmid DNA are typical.