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Replicon fusions promoted by insertion sequences on Pseudomonas cepacia plasmid pTGL6
Molecular & General Genetics : MGG
|August 1, 1986
Summary
Replication failure of plasmid pMR5 in Pseudomonas cepacia led to the formation of cointegrate plasmids. Insertion sequences on pTGL6 mediated these fusions, resulting in novel plasmid structures.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Plasmid pMR5 (pRP1ts) exhibited temperature-sensitive replication in Pseudomonas cepacia.
- P. cepacia 249 harbored a large 170 kb plasmid, pTGL6.
- Selection for tetracycline resistance at elevated temperatures induced plasmid instability.
Purpose of the Study:
- To investigate the formation and structure of cointegrate plasmids resulting from the fusion of pMR5 and pTGL6.
- To identify the role of insertion sequences in mediating plasmid cointegration.
Main Methods:
- Plasmid isolation and characterization from P. cepacia.
- Temperature-shift experiments to induce cointegrate formation.
- Southern hybridization to analyze plasmid structures and insertion sequence distribution.
Main Results:
- Cointegrate plasmids (pTGL100, pTGL101, pTGL102) were formed by the fusion of pMR5 and pTGL6.
- Insertion sequences IS401 and IS402 on pTGL6 promoted the formation of these cointegrates.
- Cointegrate plasmids contained additional copies of the fusion-mediating insertion sequences.
- Plasmid pTGL100 resolved into pTGL6 and a novel pMR5 derivative (pTGL105) containing IS401.
- Plasmid pTGL102 evolved through IS402-mediated fusion and IS411 transposition.
Conclusions:
- Insertion sequences play a crucial role in mediating the formation of cointegrate plasmids in P. cepacia.
- Plasmid cointegration and subsequent rearrangements can lead to the generation of novel plasmid structures and derivatives.
- The study elucidates mechanisms of plasmid evolution and genetic exchange within bacterial populations.