Improved antibiotic-resistance gene cassettes and omega elements for Escherichia coli vector construction and in vitro deletion/insertion mutagenesis.

Several antibiotic-resistance gene cassettes and omega elements for Escherichia coli vector construction include the aacC1, aadA+, bla, cat, nptII and tet gene cassettes, and also the omega-Gm, omega-Sm, omega-Ap, omega-Cm, omega-Km and omega-Tc elements. Both cassettes and elements are flanked by pBluescriptII plasmid multiple cloning sites (MCS) duplicated in inverted (symmetric MCS) or direct (tandem MCS) orientation. Genes that were modified in order to remove sites for the most common restriction endonucleases from their coding regions (except aacC1 and aadA+) were used for cassette and omega-element construction.