Horizontal Gene Transfer

Volume 532 of the series Methods in Molecular Biology pp 103-125

The Integron/Gene Cassette System: An Active Player in Bacterial Adaptation

  • Maurizio LabbateAffiliated withDepartment of Chemistry and Biomolecular Sciences, Macquarie University
  • , Rebecca Josephine CaseAffiliated withHarvard Center for the Environment (HUCE) and Microbiology and Molecular Genetics, Harvard Medical School, Harvard University
  • , Hatch W. StokesAffiliated withDepartment of Chemistry and Biomolecular Sciences, Macquarie University

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The integron includes a site-specific recombination system capable of integrating and expressing genes contained in structures called mobile gene cassettes. Integrons were originally identified on mobile elements from pathogenic bacteria and were found to be a major reservoir of antibiotic-resistance genes. Integrons are now known to be ancient structures that are phylogenetically diverse and, to date, have been found in approximately 9% of sequenced bacterial genomes. Overall, gene diversity in cassettes is extraordinarily high, suggesting that the integron/gene cassette system has a broad role in adaptation rather than being confined to simply conferring resistance to antibiotics. In this chapter, we provide a review of the integron/gene cassette system highlighting characteristics associated with this system, diversity of elements contained within it, and their importance in driving bacterial evolution and consequently adaptation. Ideas on the evolution of gene cassettes and gene cassette arrays are discussed.


Integron gene cassette antibiotic-resistance attC