Role of pathogenicity island‐associated integrases in the genome plasticity of uropathogenic Escherichia coli strain 536

Abstract

SummaryThe genome of uropathogenic Escherichia coli isolate 536 contains five well-characterized pathogenicity islands (PAIs) encoding key virulence factors of this strain. Except PAI IV536, the four other PAIs of strain 536 are flanked by direct repeats (DRs), carry intact integrase genes and are able to excise sitespecifically from the chromosome. Genome screening of strain 536 identified a sixth putative asnWassociated PAI. Despite the presence of DRs and an intact integrase gene, excision of this island was not detected. To investigate the role of PAI-encoded integrases for the recombination process the int genes of each unstable island of strain 536 were inactivated. For PAI I 536 and PAI II536, their respective P4-like integrase was required for their excision. PAI III536 carries two integrase genes, intA, encoding an SfX-like integrase, and intB, coding for an integrase with weak similarity to P4-like integrases. Only intB was required for site-specific excision of this island. For PAI V536, excision could not be abolished after deleting its P4-like integrase gene but additional deletion of the PAI II536-specific integrase gene was required. Therefore, although all mediated by P4-like integrases, the activity of the PAI excision machinery is most often restricted to its cognate island. This work also demonstrates for the first time the existence of a cross-talk between integrases of different PAIs and shows that this cross-talk is unidirectional.

Shaping a bacterial genome by large chromosomal replacements, the evolutionary history of Streptococcus agalactiae

“…Conjugative transfer and the replacement of hundreds of kilobases of bacterial chromosomes already have been described under laboratory conditions, but their impact on natural populations remained largely unknown (32). This work demonstrates that large conjugal exchanges have contributed significantly to the genome dynamics of S. agalactiae and strengthen the role of integrative conjugative elements in the dynamics of bacterial chromosomes (33,34). The outcome of such extensive exchanges probably depends on complex selection processes allowing transconjugants to outcompete the parental strains.…”

A subset of mucosa-associated Escherichia coli isolates from patients with colon cancer, but not Crohn's disease, share pathogenicity islands with urinary pathogenic E. coli

“…The SSH sequences included sequences that matched parts of the UPEC strain 536 PAIs PAI I 536 , PAI III 536 , PAI IV 536 , PAI V 536 and PAI VI 536 (Dobrindt et al, 2002;Brzuszkiewicz et al, 2006;Hochhut et al, 2006) and the UPEC strain CFT073 PAIs PAI I CFT073 (Guyer et al, 1998) and PAI II CFT073 (Rasko et al, 2001).…”

“…DQ126339), but for which there is no publication. Three further SSH sequences matched integrases, including one (SSH229-26) that matched a P4-like PAI-associated integrase similar to those implicated in playing an important role in the plasticity of E. coli genomes (Hochhut et al, 2006;Manson & Gilmore, 2006).…”

tDNA locus polymorphism and ecto-chromosomal DNA insertion hot-spots are related to the phylogenetic group of Escherichia coli strains

“…Indeed, the activity of integrase genes found in several genomic islands and involved in genomic islands mobility is likely to depend upon the DNA structure (Cali et al, 2004;Hochhut et al, 2006;Lesic et al, 2004;Pribil & Haniford, 2003;Radman-Livaja et al, 2006). Interestingly, several tDNA loci with high scores such as alaX, glyY, lysQ, proM, thrT, valW or glnX had DNA curvature profiles different from those of a number of loci with low scores such as asn loci, pheU, metV, pheV and serW.…”