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On the origin of the chloramphenicol resistance transposon Tn9
Abstract:
The widely studied chloramphenicol resistance (Cmr) transposon Tn9 came from phage P1Cm0. This phage, however, had acquired its Cmr marker from the R plasmid pSM14. The analysis of the physical structure of pSM14 has now revealed that this plasmid already carried Tn9 and also the tetracycline resistance transposon Tn10. Physical and functional studies indicated that Tn9 of pSM14, although capable of transposition, probably translocated to the P1 genome by reciprocal recombination processes.
Insights
The chloramphenicol resistance transposon Tn9 originated from phage P1Cm0, which acquired it from plasmid pSM14. This plasmid also contained Tn10, and Tn9 likely moved to the phage genome via recombination.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The chloramphenicol resistance (Cmr) transposon Tn9 is widely studied.
- Tn9 is known to have originated from phage P1Cm0.
- Phage P1Cm0 acquired its Cmr marker from the R plasmid pSM14.
Purpose of the Study:
- To investigate the physical structure of the R plasmid pSM14.
- To understand the origin and transfer mechanisms of the Tn9 transposon.
- To elucidate the relationship between plasmid pSM14, transposon Tn9, and phage P1Cm0.
Main Methods:
- Physical mapping of plasmid pSM14.
- Functional analysis of transposon activity.
- Comparative genomic analysis.
Main Results:
- Plasmid pSM14 was found to harbor both Tn9 and the tetracycline resistance transposon Tn10.
- Tn9 on pSM14 was capable of transposition.
- Evidence suggests Tn9 translocated from pSM14 to the P1 genome through reciprocal recombination.
Conclusions:
- The R plasmid pSM14 is the source of the Tn9 transposon found in phage P1Cm0.
- Tn9 and Tn10 coexisted on plasmid pSM14.
- Reciprocal recombination is the probable mechanism for Tn9 transfer from pSM14 to P1.