%0 Journal Article
%T Lambda Red-mediated recombinogenic engineering of enterohemorrhagic and enteropathogenic E. coli
%A Kenan C Murphy
%A Kenneth G Campellone
%J BMC Molecular Biology
%D 2003
%I BioMed Central
%R 10.1186/1471-2199-4-11
%X In this report, we have identified conditions that optimize the use of ¦Ë Red for recombineering in EHEC and EPEC. Using plasmids that contain a Ptac-red-gam operon and a temperature-sensitive origin of replication, we have generated multiple mutations (both marked and unmarked) in known virulence genes. In addition, we have easily deleted five O157-specific islands (O-islands) of EHEC suspected of containing virulence factors. We have examined the use of both PCR-generated substrates (40 bp of flanking homology) and plasmid-derived substrates (~1 kb of flanking homology); both work well and each have their own advantages. The establishment of the hyper-rec phenotype requires only a 20 minute IPTG induction period of red and gam. This recombinogenic window is important as constitutive expression of red and gam induces a 10-fold increase in spontaneous resistance to rifampicin. Other factors such as the orientation of the drug marker in recombination substrates and heat shock effects also play roles in the success of Red-mediated recombination in EHEC and EPEC.The ¦Ë Red recombineering technology has been optimized for use in pathogenic species of E. coli, namely EHEC and EPEC. As demonstration of this technology, five O-islands of EHEC were easily and precisely deleted from the chromosome by electroporation with PCR-generated substrates containing drug markers flanked with 40 bp of target DNA. These results should encourage the use of ¦Ë Red recombineering in these and other strains of pathogenic bacteria for faster identification of virulence factors and the speedy generation of bacterial mutants for vaccine development.A new method for engineering bacterial chromosomes has emerged in recent years that takes advantage of the high proficiency of bacteriophage recombination systems acting on linear DNA substrates [see reference [1] for review]. The ¦Ë Red recombination system, consisting of Bet (a ssDNA annealing protein) and Exo (a 5'-3' dsDNA exonuclease) promotes gene
%U http://www.biomedcentral.com/1471-2199/4/11