A broad-host-range Flp-FRT recombination system for site-specific excision of chromosomally-located DNA sequences: application for isolation of unmarked Pseudomonas aeruginosa mutants

Gene. 1998 May 28;212(1):77-86. doi: 10.1016/s0378-1119(98)00130-9.


An improved method for gene replacement in Pseudomonas aeruginosa was developed. The method employs several new gene replacement vectors that incorporate (1) the counterselectable sacB marker, (2) a lacZ alpha-allele for blue-white screening, (3) the pUC18/19 vectors multiple cloning site with 10 unique restriction sites, (4) an oriT for conjugation-mediated plasmid transfer and (5) carbenicillin, gentamicin (Gm) and tetracycline selectable markers. A cassette was constructed that contains a GmR selectable marker next to the green fluorescent protein structural gene, with both markers being flanked by Flp recombinase target (FRT) sites. The FRT cassette was used to insertionally inactivate the cloned P. aeruginosa pabC gene encoding aminodeoxychorismate lyase. After conjugal transfer into P. aeruginosa, plasmid integrants were selected, and deletion of unwanted DNA sequences was promoted by sucrose counterselection. The FRT cassette was excised with high frequencies (close to 100%) from the chromosome after conjugal transfer of a Flp recombinase-expressing plasmid; this sacB-containing plasmid was subsequently cured by sucrose counterselection, resulting in an unmarked P. aeruginosa delta pabC strain.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Chromosome Mapping
  • DNA Nucleotidyltransferases / genetics
  • DNA Primers / genetics
  • DNA, Bacterial / genetics*
  • Escherichia coli / genetics
  • Genes, Bacterial
  • Genetic Markers
  • Genetic Techniques
  • Genetic Vectors
  • Molecular Sequence Data
  • Mutation*
  • Plasmids / genetics
  • Pseudomonas aeruginosa / genetics*
  • Recombination, Genetic*


  • DNA Primers
  • DNA, Bacterial
  • Genetic Markers
  • DNA Nucleotidyltransferases
  • FLP recombinase

Associated data

  • GENBANK/AF047518
  • GENBANK/AF047519
  • GENBANK/AF048702