Interstrain transfer of the large pathogenicity island (PAPI-1) of Pseudomonas aeruginosa

Abstract

The large Pseudomonas aeruginosa pathogenicity island PAPI-1 of strain PA14 is a cluster of 108 genes that encode a number of virulence features. We demonstrate that, in a subpopulation of cells, PAPI-1 can exist in an extrachromosomal circular form after precise excision from its integration site within the 3 terminus of the tRNA Lys gene. Circular PAPI-1 can reintegrate into either of the two tRNA Lys genes, including the one that was used for integration of small pathogenicity island PAPI-2 in strain PA14. The excision requires PAPI-1-encoded integrase, a member of the tyrosine recombinase family. PAPI-1 Soj contains the conserved domains of proteins that are related to chromosome and plasmid partition. soj plays a role in maintaining PAPI-1 and mutations in soj result in the loss of PAPI-1 from P. aeruginosa. We further demonstrate that, during coculture, the PAPI-1-containing strains are able to transfer it into P. aeruginosa recipient strains that do not harbor this island naturally. After transfer, PAPI-1 integrates into either of the two tRNA Lys genes. PAPI-1 encompasses many features of mobile elements, including mobilization and maintenance modules. Together with the virulence determinants, PAPI-1 plays an important role in the evolution of P. aeruginosa, by expanding its natural habitat from soil and water to animal and human infections.evolution ͉ horizontal gene transfer ͉ integration

Accurate localization and excision of genomic islands in four strains of Pseudomonas aeruginosa and Pseudomonas fluorescens

“…Webb et al [14] extracted the replicative-form (RF) DNA of Pf4 (PAO1GI-1) from Pf4-infected cells, and used primers Pf4F and Pf4R to confirm recirculation of prophage Pf4 by the repeat sequence (3′-TGGAGCGGGCGAAGGGAATCGAACCCT-5′). This result was similar to our study, however, we selected a more precise crossing-combining approach of primers [11], and also determined that PAO1GI-1 (prophage Pf4) not only exists in the chromosome, but also can be excised from the chromosome to form a circular intermediate. Mathee et al [21] also found a similar region (RGP5) with PAO1GI-1 ( Table 4) that only determined the excision of RGP5 from the genome.…”

“…Further, the circular intermediate was not detected by Mathee et al [21] because GIs with unclear boundaries were identified and crossing-combining primers were nonspecific resulting in the inability to produce all four amplification products, including the circular intermediates. PA14GI-4, namely PAPI-1, was also determined similarly [11]. We also designed primers to determine the mobility of PAOGI-2 and Pf0-1GI-1, but our study revealed that these 2 GIs were not deleted from the chromosomes proving that Rve family proteins may not catalyze the excision of GIs.…”

“…In the current study, we selected a crossing-combining approach of primers to determine whether the GIs were mobile [11]. A set of PCR primers were designed to determine whether PAO1GI-1, Pf5GI-1, Pf5GI-2, Pf5GI-3, and Pf5GI-4 were present in the chromosome and whether they can be excised from the chromosome ( Table 2).…”

“…We show that 1 GI of P. aeruginosa PAO1 and 3 GIs of P. fluorescens Pf-5 can be excised from the chromosome to form a circular intermediate by the crossing-combining approach of primers [11]. Through the accurate localization of the GI flanking sequences, the action sites of the integrases of GIs can be predicted.…”

Epidemic Spread of Symbiotic and Non-Symbiotic Bradyrhizobium Genotypes Across California

“…The acquisition of plasmids and genomic islands has been implicated in epidemic outbreaks, including Pseudomonas aeruginosa, Staphylococcus aureus, and Yersinia spp. [6][7][8]. But in natural settings, we understand little about how bacterial strains vary in their capacity to dominate local sites or host populations or to spread among sites across ecological barriers.…”