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Pathogenicity islands of virulent bacteria: structure, function and impact on microbial evolution
J Hacker1, G Blum-Oehler, I Mühldorfer
1Institut für Molekulare Infektionsbiologie, Röntgenring, Würzburg, Germany. j.hacker@rzbox.uni-wuerzburg.de
Molecular Microbiology
|March 1, 1997
Summary
Pathogenicity islands (Pais) are large DNA regions in bacterial genomes that contain virulence genes. These islands are found in pathogenic bacteria but not in non-pathogenic strains, indicating their role in bacterial disease.
Area of Science:
- Microbiology
- Genetics
- Molecular Biology
Background:
- Virulence genes in pathogenic bacteria encode toxins, adhesins, and invasins.
- These genes can reside on mobile genetic elements or within specific chromosomal regions called pathogenicity islands (Pais).
- Pais are characteristic of pathogenic bacterial strains and are largely absent in non-pathogenic relatives.
Purpose of the Study:
- To describe the characteristics and genomic location of pathogenicity islands.
- To elucidate the role of pathogenicity islands in bacterial virulence and evolution.
- To understand the mechanisms of pathogenicity island acquisition and maintenance.
Main Methods:
- Comparative genomics to identify Pais in pathogenic vs. non-pathogenic strains.
- Analysis of Pais' DNA composition (e.g., G+C content) and flanking sequences.
- Investigation of Pais' association with mobile genetic elements and tRNA loci.
Main Results:
- Pathogenicity islands are large DNA segments (up to 200 kb) often containing multiple virulence genes.
- Pais exhibit distinct G+C content compared to the rest of the bacterial genome and are frequently flanked by direct repeats or insertion sequence elements.
- These islands are often integrated at tRNA loci and show evidence of horizontal gene transfer.
Conclusions:
- Pathogenicity islands are key genetic elements driving bacterial pathogenicity and evolution.
- Their structure and location facilitate their spread and integration into bacterial genomes.
- Understanding Pais is crucial for developing strategies against bacterial infections.