Smith/Birnstiel mapping of genome rearrangements in Pseudomonas aeruginosa

A novel application of the Smith/Birnstiel technique is presented for the analysis of intraspecies genomic diversity in small genomes. Rare-cutter total/N frequent-cutter partial restriction digestions are separated in N separate lanes by pulsed-field gel electrophoresis, blotted and hybridized with rare-cutter fragment ends as probes. The evaluation of the autoradiogram results in high-resolution restriction maps of 10-200 kbp regions. The technique was applied to the analysis of genome rearrangements in Pseudomonas aeruginosa strains. Comparison of the region encoding the tryptophan biosynthesis genes in the PAO and the IATS serotype 5 strains revealed that shared sequence characterized by almost identical restriction fingerprints was interrupted in the serotype 5 strain by small islands displaying strain-specific restriction site signatures. A multistep rearrangement in a hypervariable chromosome region downstream of the phn locus was detected in serial airway isolates from a patient with cystic fibrosis.