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Family of class 1 integrons related to In4 from Tn1696

S R Partridge1, G D Recchia, H W Stokes

  • 1CSIRO Molecular Science, North Ryde, New South Wales 2113, Australia.

Antimicrobial Agents and Chemotherapy
|October 16, 2001
PubMed

Insights

Class 1 integrons, like In28 and In1, are mobile genetic elements found in multidrug resistance transposons. These integrons show structural variations and gene cassette content, often resulting from deletions and transposition events.

Area of Science:

  • Microbiology
  • Genetics
  • Molecular Biology

Background:

  • Class 1 integrons are key elements in the dissemination of antimicrobial resistance genes.
  • Integrons are often associated with mobile genetic elements like transposons and plasmids.
  • Previous studies have characterized various class 1 integrons, highlighting their structural diversity.

Purpose of the Study:

  • To analyze the structure and genetic context of the class 1 integron In28.
  • To compare In28 with other related integrons, such as In4 and In1.
  • To understand the mechanisms of integron evolution and gene cassette acquisition.

Main Methods:

  • Sequence analysis of the integron In28 within the transposon Tn1403.
  • Comparative analysis of integron sequences from databases.
  • Identification of flanking direct repeats and associated mobile genetic elements.

Main Results:

  • Integron In28 is located in the res site of transposon Tn1403, flanked by a 5-bp direct duplication, suggesting transposition.
  • In28 exhibits structural similarities to In4 but has undergone IS6100-mediated deletions, losing the sul1 gene and a partial IS6100 copy.
  • In28 contains the gene cassettes blaP1, cmlA1, and aadA1; In1, found in plasmid R46, also resides in a res site and shows internal deletions.
  • Database searches revealed other In4-related integrons with similar deletions, and Tn610 belongs to this group.

Conclusions:

  • Class 1 integrons display significant structural plasticity due to deletions and transposition.
  • The res site appears to be a common integration site for class 1 integrons within transposons.
  • Integron evolution involves the loss of internal sequences and genetic elements, contributing to their diversity.

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