Integration of PCR products and antibiotic resistance gene excision in E. coli. (A) Deletion of msbB using a PCR product with homology to the regions flanking chromosomal msbB to generate DH1M. (B) Agarose gel of PCR products generated using primers SML and SMR. Lane 1, negative control (no template DNA); lane 2, wild-type msbB locus; lane 3, integrant; lane 4, deletion mutant. (C) Chromosomal insertion of rbpA using a PCR product with homology to the ubiB-fadR intergenic region to generate DH1R. (D) Agarose gel of PCR products generated using primers UbiB F and UbiB R. Lane 1, negative control (no template DNA); lane 2, wild-type ubiB-fadR locus; lane 3, integrant; lane 4, recombinant with inserted rbpA.