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Identification of oriT and a recombination hot spot in the IncA/C plasmid backbone

Anna Hegyi1, Mónika Szabó1, Ferenc Olasz1

  • 1Agricultural Biotechnology Institute, National Agricultural Research and Innovation Centre, 4. Szent-Györgyi Albert str., Gödöllő, Hungary.

Scientific Reports
|September 8, 2017
PubMed

Insights

Researchers identified the origin of transfer (oriT) locus on IncA/C plasmids, crucial for spreading antibiotic resistance in bacteria. This finding helps understand how resistance genes move between bacterial cells.

Area of Science:

  • Molecular Biology
  • Genetics
  • Microbiology

Background:

  • Antibiotic resistance is rapidly spreading in pathogenic bacteria, facilitated by mobile genetic elements like plasmids.
  • IncA/C plasmids are broad-host-range conjugative plasmids known to carry resistance genes, but their transfer mechanisms are poorly understood.
  • The precise location and function of the origin of transfer (oriT) on these plasmids remain unidentified.

Purpose of the Study:

  • To identify and characterize the origin of transfer (oriT) locus on IncA/C plasmids.
  • To investigate the functional elements within the oriT region responsible for plasmid transfer.
  • To identify other functional loci on the IncA/C plasmid backbone.

Main Methods:

  • Bioinformatic analysis of sequenced IncA/C plasmids.
  • Identification of conserved sequence motifs and regulatory regions.
  • Functional assays to test transfer activity of identified DNA regions.

Main Results:

  • A single oriT locus was identified immediately upstream of the mobI gene, essential for plasmid transfer.
  • The functional oriT spans approximately 150 bp, featuring an AT-rich region with multiple repeats.
  • A distinct 70-bp core domain within oriT retains significant transfer activity, containing specific repeat structures.
  • A second recombination site, mimicking oriT function, was identified and characterized as a RecA-independent recombination locus.

Conclusions:

  • The study precisely locates the oriT on IncA/C plasmids, elucidating a key step in their conjugative transfer.
  • The identified oriT structure provides insights into the molecular mechanisms of plasmid dissemination.
  • A novel recombination site distinct from oriT was discovered, contributing to the understanding of plasmid dynamics.

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