Related Experiment Videos
Lambda Red-mediated recombinogenic engineering of enterohemorrhagic and enteropathogenic E. coli
Kenan C Murphy1, Kenneth G Campellone
1Department of Molecular Genetics and Microbiology, University of Massachusetts Medical School, Worcester, MA 01655, USA. kenan.murphy@umassmed.edu
BMC Molecular Biology
|December 16, 2003
Summary
Lambda Red recombineering is now optimized for pathogenic E. coli (EHEC, EPEC). This method efficiently generates deletion mutants and aids in identifying virulence factors for vaccine development.
Area of Science:
- Microbiology
- Molecular Biology
- Bacterial Genetics
Background:
- Lambda Red recombineering is widely used in E. coli and Salmonella typhimurium for creating deletion mutants.
- Its application in pathogenic E. coli strains like Enterohemorrhagic E. coli (EHEC) and Enteropathogenic E. coli (EPEC) has yielded inconsistent results.
- This study aimed to identify factors enhancing Red recombineering efficiency in these pathogenic strains.
Purpose of the Study:
- To optimize lambda Red recombineering for efficient genetic manipulation in EHEC and EPEC.
- To identify key factors influencing the success of Red-mediated recombination in pathogenic E. coli.
- To demonstrate the utility of optimized recombineering for virulence gene studies and mutant generation.
Main Methods:
- Utilized plasmids with a Ptac-red-gam operon and a temperature-sensitive origin of replication.
- Employed both PCR-generated (40 bp homology) and plasmid-derived (approx. 1 kb homology) recombination substrates.
- Investigated the impact of IPTG induction time, drug marker orientation, and heat shock on recombination efficiency.
Main Results:
- Optimized conditions for lambda Red recombineering in EHEC and EPEC were identified.
- Multiple marked and unmarked mutations were generated in virulence genes.
- Successfully deleted five O157-specific islands (O-islands) from EHEC.
- Demonstrated that a 20-minute IPTG induction for red and gam expression is sufficient for the hyper-recombinogenic phenotype.
- Showed that constitutive expression of red and gam increases spontaneous rifampicin resistance.
Conclusions:
- Lambda Red recombineering technology is now optimized for pathogenic E. coli (EHEC, EPEC).
- The optimized method allows for precise deletion of genomic regions, such as virulence factor-containing O-islands.
- This advancement facilitates rapid identification of virulence factors and accelerates the generation of bacterial mutants for vaccine development.