Spread of Pathogenicity Islands in Escherichia coli

Escherichia coli The species Escherichia coli comprises non-pathogenic, commensal bacterial strains belonging to the normal gut microbiota of humans and many animals, but also pathogenic strains, which cause different types of intestinal or extraintestinal infections in man and animals. Single factors and mechanisms involved in pathogenesis of extraintestinal pathogenic E. coli (ExPEC) have been analyzed in detail for many years. Horizontal gene transfer is a key step in the evolution of bacterial pathogens. Besides phages and plasmids, pathogenicity islands (PAIs) are subjected to horizontal transfer. The transfer mechanisms of PAIs within a certain bacterial species or between different species are still not well understood.

In a new study the authors applied a phylogenetic approach using multilocus sequence typing on HPI-positive and -negative natural E. coli isolates representative of the species diversity to infer the mechanism of horizontal HPI transfer within the E. coli species. In each strain, the partial nucleotide sequences of 6 HPI–encoded genes and 6 housekeeping genes of the genomic backbone, as well as DNA fragments immediately upstream and downstream of the HPI were compared. This revealed that the HPI is not solely vertically transmitted, but that recombination of large DNA fragments beyond the HPI plays a major role in the spread of the HPI within E. coli species. In support of the results of the phylogenetic analyses, they demonstrated that HPI can be transferred between different E. coli strains by F-plasmid mediated mobilization. Sequencing of the chromosomal DNA regions immediately upstream and downstream of the HPI in the recipient strain indicated that the HPI was transferred and integrated together with HPI–flanking DNA regions of the donor strain. The results of this study demonstrate for the first time that conjugative transfer and homologous DNA recombination play a major role in horizontal transfer of a pathogenicity island within the species E. coli.

Role of Intraspecies Recombination in the Spread of Pathogenicity Islands within the Escherichia coli Species. 2009 PLoS Pathog 5(1): e1000257

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2 Responses to Spread of Pathogenicity Islands in Escherichia coli

  1. Clayton says:

    Dr. Cann,

    Firstly, thanks for your continued efforts to post relevant and timely stories. While my comment is not directly related to this post I was actually wondering if there was a search feature for your blog? Maybe I am just blind, but I have looked for one to no avail. A search feature (*if not already available) would be extremely useful seeing as how it would take a considerable amount of time to click through the archives to find what I want. Please disregard and accept my apologies if I have failed to see the obvious. Finally, while I don’t frequently comment on the site I do read the posts and access the linked papers when possible. I know that you would appreciate more user feedback and will try my best to take the time to comment in the future.
    Thanks,

    -Clayton

  2. ajcann says:

    Yes! The link is the top left of each page (“Search”).

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