Horizontal transfer of Yersinia high‐pathogenicity island by the conjugative RP4 attB target‐presenting shuttle plasmid

Abstract

SummaryThe high-pathogenicity island (HPI) encodes a highly efficient yersiniabactin system of iron acquisition responsible for mouse lethality in Yersinia . Although the HPI is widely disseminated among Enterobacteriaceae it lacks functions necessary for its replication and transmission. Therefore, the mechanism of its horizontal transfer and circulation is completely obscure. On the other hand, the HPI is a genetically active island in the bacterial cell. It encodes a functional recombinase and is able to transpose to new targets on the chromosome. Here we report on a possible mechanism of the HPI dissemination based on site-specific recombination of the excised HPI with the attB -presenting ( asn tRNA gene) RP4 promiscuous conjugative shuttle plasmid. The resulting cointegrate can be transferred by conjugation to a new host, where it dissociates, and the released HPI integrates into any unoccupied asn tRNA gene target in the genome. This mechanism has been proven both with the 'mini' island carrying only the attP recognition site and genes coding for recombination enzymes and with the complete HPI labelled with an antibiotic resistance marker. After acquisition of the mobilized complete form of the HPI, the ability of the HPI-cured Yersinia enterocolitica WA-TH -strain to produce yersiniabactin has been restored. Such 'trapping' of pathogenicity islands and subsequent shuffling to new hosts by a conjugative replicon carrying a suitable attB site could be applied to other functional integrative elements and explain wide dissemination of PAIs.

Characterization of Integrative and Conjugative Element ICEKp1-Associated Genomic Heterogeneity in aKlebsiella pneumoniaeStrain Isolated from a Primary Liver Abscess

“…However, the HPI carried in the ICE was restricted to a single E. coli strain, and conjugative transfer of this ICE has not been demonstrated. Another study reported a possible mechanism of HPI dissemination based on site-specific recombination of the excised HPI with the attB-presenting RP4 conjugative shuttle plasmid (2). The authors hypothesized that the general model for "trapping" the PAI on a conjugative plasmid bearing an attB site could also explain the dissemination of other PAIs.…”

Independent acquisition of site-specific recombination factors by asn tRNA gene-targeting genomic islands

“…asn tRNA gene (Antonenka et al, 2005). The number of cointegrate-carrying clones after conjugation reflects the initial ability of each construct to excise from the host chromosome and to cointegrate with the RP4 attB shuttle plasmid In the case of pKR529 orf1-5r and pKR529 orf2 constructs, we observed the highest transfer efficiency (25 Â 10 À7 -29 Â 10 À7 ) compared to 47 Â 10 À8 -55 Â 10 À8 observed with the constructs that did not carry the functional ORF2.…”

“…Typically bacteria were cultivated in Luria-Bertani (LB) medium or on LB agar plates (Difco Laboratories, Detroit, Michigan) at 28 1C for Yersinia or 37 1C for E. coli. Antonenka et al (2005) Plasmid construct for excisionase protein purification…”

Reticulate evolution is favored in influenza niche switching

“…In contrast to clonal adaptation through genetic drift over time, reticulate evolutionary processes allow an organism to acquire independently evolved genetic material that can confer new fitness-enhancing traits. Examples include the acquisition of cell surface receptor adaptations (point mutations) in viruses (3) and antibiotic resistance (single genes) (4) and pathogenicity islands (or gene clusters) in bacteria (5). Host switching, defined as a pathogen moving from one host species into another, represents a fitness barrier to microbial pathogens.…”