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Molecular characterization of the class II multiresistance transposable element Tn1403 from Pseudomonas aeruginosa
1Département de Microbiologie, Faculté de Médecine, Université Laval, Québec, Canada.
Abstract:
Transposon Tn1403 is a 19.9-kb multiresistance class II transposable element originally found on the RPL11 plasmid from a clinical isolate of Pseudomonas aeruginosa. It encodes resistance to ampicillin (PSE-1 beta-lactamase), streptomycin and spectinomycin (aadA and aphC), and chloramphenicol (cat). It has structural homology with the tnpM and tnpI sequences of Tn21 and inverted repeats and res and tnpR sequences of Tn501, but it has no structural homology nor functional complementation with the resolvase gene of Tn21 or Tn3. Sequence analysis revealed long inverted repeats at each extremity of Tn1403 containing 38-bp inverted repeats that were 97.4% similar to those of Tn1721 and 5-bp direct repeats. Transposition assays showed a low frequency of transposition (3.5 x 10(-6)) compared with that of Tn3 (3.3 x 10(-3)) and no resolution of cointegrates.
Insights
Transposon Tn1403, a multiresistance element in Pseudomonas aeruginosa, confers resistance to ampicillin, streptomycin, spectinomycin, and chloramphenicol. Its low transposition frequency and lack of cointegrate resolution distinguish it from related elements.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Transposon Tn1403 is a class II transposable element identified on the RPL11 plasmid in a clinical isolate of Pseudomonas aeruginosa.
- It confers resistance to multiple antibiotics: ampicillin (PSE-1 beta-lactamase), streptomycin and spectinomycin (aadA and aphC), and chloramphenicol (cat).
Purpose of the Study:
- To characterize the genetic structure and transpositional behavior of Tn1403.
- To compare Tn1403 with other known transposable elements like Tn21, Tn501, Tn1721, and Tn3.
Main Methods:
- Sequence analysis of Tn1403 to identify structural features and homologies.
- Transposition assays to quantify its frequency and assess cointegrate resolution capabilities.
Main Results:
- Tn1403 exhibits structural homology with Tn21 (tnpM, tnpI) and Tn501 (inverted repeats, res, tnpR) but lacks homology/complementation with the Tn21/Tn3 resolvase gene.
- Sequence analysis revealed long inverted repeats at its extremities, with 38-bp inverted repeats 97.4% similar to Tn1721 and 5-bp direct repeats.
- Transposition assays demonstrated a low transposition frequency (3.5 x 10(-6)) compared to Tn3 (3.3 x 10(-3)) and no resolution of cointegrates.
Conclusions:
- Tn1403 is a distinct multiresistance transposon with unique structural and functional characteristics.
- Its low transposition efficiency and inability to resolve cointegrates suggest a limited role in rapid dissemination of resistance genes compared to other class II transposons.