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Characterization of a ColE1-like plasmid isolated from Shigella sonnei
Abstract:
A multicopy plasmid, 4.7 kb in size, was isolated from Shigella sonnei and named pKY1. This plasmid produces a colicin E1-like bacteriocin (colicin E1*) in E. coli cells. The cells harboring pKY1 are immune not only to this bacteriocin but also to colicin E1, and the cells harboring Co1E1 show immunity to colicin E1* as well. Although these two plasmid DNAs have different cleavage maps and are compatible with each other, pKY1 shows partial DNA homology with ColE1 DNA. In this paper, we report the isolation and properties of several Tn3 inserted pKY1 mutants, and propose a preliminary genetic map of pKY1. It was also found that this plasmid is not capable of self-transmission and is poorly mobilized by the F factor.
Insights
Researchers isolated plasmid pKY1 from Shigella sonnei, which produces a colicin E1-like bacteriocin and confers immunity to related colicins. Tn3 mutagenesis helped map pKY1
Area of Science:
- Microbiology
- Molecular Biology
- Bacteriophage Research
Background:
- Shigella sonnei harbors a multicopy plasmid, designated pKY1, with potential implications for bacterial interactions.
- Colicins are bacteriocins produced by Escherichia coli that exhibit antimicrobial activity, with implications for microbial ecology and pathogenesis.
- Plasmid compatibility and DNA homology are crucial factors in understanding plasmid maintenance and evolution within bacterial populations.
Purpose of the Study:
- To isolate and characterize a novel plasmid, pKY1, from Shigella sonnei.
- To investigate the bacteriocin production and immunity properties conferred by pKY1.
- To construct and analyze Tn3 insertion mutants of pKY1 to establish a preliminary genetic map.
Main Methods:
- Isolation and characterization of a 4.7 kb multicopy plasmid (pKY1) from Shigella sonnei.
- Expression of colicin E1-like bacteriocin (colicin E1*) in E. coli and assessment of immunity conferred by pKY1 and ColE1.
- Generation of Tn3 insertion mutants of pKY1 and analysis of DNA homology with ColE1 DNA.
Main Results:
- Plasmid pKY1 was isolated and shown to produce a colicin E1-like bacteriocin (colicin E1*).
- Cells harboring pKY1 exhibited immunity to both colicin E1* and colicin E1; conversely, cells with ColE1 were immune to colicin E1*.
- Despite different cleavage maps and compatibility, pKY1 displayed partial DNA homology with ColE1 DNA. Tn3 mutagenesis yielded mutants, enabling the proposal of a preliminary genetic map for pKY1.
- Plasmid pKY1 demonstrated no self-transmission capability and poor mobilization by the F factor.
Conclusions:
- Plasmid pKY1 confers unique bacteriocin production and immunity characteristics, suggesting a role in inter-bacterial competition.
- The partial DNA homology and functional cross-immunity between pKY1 and ColE1 indicate a genetic relationship.
- The development of a preliminary genetic map through Tn3 mutagenesis provides a foundation for further functional studies of pKY1.
- The inability of pKY1 to self-transmit or be efficiently mobilized suggests limited horizontal gene transfer potential via conjugation.