title: Simple generation of site-directed point mutations in the Escherichia coli chromosome using Red(R)/ET(R) Recombination.
abstract: BACKGROUND
  Introducing point mutations into bacterial chromosomes is important for further progress in studies relying on functional genomics, systems- and synthetic biology, and for metabolic engineering. For many investigations, chromosomal systems are required rather than artificial plasmid based systems.
  
  
  RESULTS
  Here we describe the introduction of a single point mutation into the Escherichia coli chromosome by site-directed mutagenesis without leaving any selection marker. We used Red(R)/ET(R) Recombination in combination with rpsL counter-selection to introduce a single point mutation into the E. coli MG1655 genome, one of the widely used bacterial model strains in systems biology. The method we present is rapid and highly efficient. Since single-stranded synthetic oligonucleotides can be used for recombination, any chromosomal modification can be designed.
  
  
  CONCLUSIONS
  Chromosomal modifications performed by rpsL counter-selection may also be used for other bacteria that contain an rpsL homologue, since Red(R)/ET(R) Recombination has been applied to several enteric bacteria before.
authors.affiliation: Ludwig-Maximilians-Universität München, Department Biologie I, Bereich Mikrobiologie, Maria-Ward-Str, 1a, D-80638 München, Germany. heermann@lmu.de.
authors.forename: Ralf
authors.initials: R
authors.lastname: Heermann
authors.forename: Tim
authors.initials: T
authors.lastname: Zeppenfeld
authors.forename: Kirsten
authors.initials: K
authors.lastname: Jung