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Cointegrational transduction and mobilization of gentamicin resistance plasmid pWP14a is mediated by IS140
Abstract:
The structures of two R-plasmids pWP14a and pWP12a (Tra-, Ap, Gm; 21 kb) and of several cointegrates they form with bacteriophages P1Cm and P1-15 were analyzed. In each case, replicon fusion was mediated by the element IS140 (about 0.8 kb), one copy of which resides on both plasmids adjacent to the gentamicin resistance determinant (AAC(3)-III). pWP14a cointegrated preferentially into or near the invertible C-loop structure of the P1 genome. Cointegrational mobilization of pWP14a was observed also with several conjugative R-factors. The process of replicon fusion is independent of the host's rec+ functions. Sequences homologous to IS140 are constituents of many R-factors, including RA1, R40a, R124, R144, Rts1, N3, and pJR255. IS140 also shows homology to two other sequences, IS15 delta and Tn2680, but not to other, well studied transposable elements. The ampicillin resistance determinant of pWP14a is within a Tn3-like transposon, Tn3651.
Insights
The IS140 element mediates replicon fusion between R-plasmids and bacteriophages, independent of host rec+ functions. This element is found in numerous R-factors and related to other mobile sequences, aiding in plasmid cointegration.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- R-plasmids are key vectors for antibiotic resistance gene transfer.
- Bacteriophage P1 is a well-studied model system for genetic manipulation.
- Understanding plasmid-bacteriophage interactions is crucial for controlling antimicrobial resistance.
Purpose of the Study:
- To analyze the structures of R-plasmids pWP14a and pWP12a.
- To investigate cointegrate formation between these R-plasmids and bacteriophages P1Cm and P1-15.
- To elucidate the mechanism of replicon fusion mediated by the IS140 element.
Main Methods:
- Plasmid and bacteriophage DNA analysis.
- Identification of insertion sequences involved in cointegration.
- Characterization of resistance determinants and transposons.
Main Results:
- Replicon fusion was mediated by the IS140 element (0.8 kb) present on both R-plasmids.
- pWP14a preferentially cointegrated into the P1 genome's C-loop structure.
- IS140 sequences show homology to many R-factors and other mobile elements like IS15 delta and Tn2680.
- The ampicillin resistance determinant in pWP14a is part of a Tn3-like transposon, Tn3651.
- Replicon fusion occurred independently of host rec+ functions.
Conclusions:
- IS140 is a significant mobile element mediating R-plasmid and bacteriophage cointegration.
- The findings provide insights into the mechanisms of genetic exchange and the evolution of R-plasmids.
- IS140's prevalence in various R-factors highlights its role in spreading antibiotic resistance.