Gene cloning and containment properties of plasmid Col E1 and its derivatives.

Colicinogenic plasmid E1 (Col E1) and Col E1 derivatives offer advantages as plasmid cloning vehicles with regard to both utility and biological containment. The Col E1 derivative pCR1 does not alter those essential characteristics of the enfeebled Escherichia coli strain x1776 that make this strain particularly useful as a host-vehicle system for recombinant DNA research.