A suitable method for construction and cloning hybrid plasmids containing EcoRI-fragments of E. coli genome.

A convenient procedure for the isolation of specific EcoRI-fragments of E. coli genome and their amplification on Km-resistance plasmid victor CK delta11 is described. The hybrid molecules were constructued in vitro using EcoRI-digestion, followed by ligation. Then appropriated E. coli strain was transformed with ligated DNA mixture and hybrid plasmids CK delta11-arg+, CK delta11-his+, CK delta11-thr+ and CK delta11-leu+ containing loci of E. coli genome were selected by molecular cloning. The hybrid plasmids obtained consisted of one EcoRI-fragment of initial plasmid CK delta11 and one respective specific portion of E. coli genome.