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A conjugative 'plasmid' lacking autonomous replication
Journal of General Microbiology
|October 1, 1981
Summary
IncJ plasmids, like R391, integrate into the bacterial chromosome, explaining why isolating them as separate DNA is difficult. This integration allows them to move bacterial genes in a specific direction.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- IncJ plasmids are a group of genetic elements found in bacteria.
- Previous studies have attempted to isolate plasmid DNA from strains carrying IncJ plasmids without success.
Purpose of the Study:
- To investigate the physical state of IncJ plasmids within bacterial hosts.
- To understand the reasons behind the failure to isolate IncJ plasmid DNA.
Main Methods:
- Attempts to isolate open and covalently closed circular DNA from bacterial strains containing IncJ plasmids.
- Experiments to assess the integration capability of the IncJ plasmid R391 into the Escherichia coli K12 chromosome.
- Analysis of the mobilization of chromosomal markers by the integrated IncJ plasmid.
Main Results:
- Standard methods failed to isolate IncJ plasmid DNA in its circular form.
- The IncJ plasmid R391 demonstrated the ability to integrate into the Escherichia coli K12 chromosome.
- Integrated R391 mobilized chromosomal markers directionally from a single origin.
Conclusions:
- IncJ plasmids likely exist primarily integrated within the bacterial chromosome.
- Chromosomal integration explains the persistent difficulty in isolating IncJ plasmid DNA.
- This integration mechanism may play a role in bacterial gene transfer and genome evolution.