The unique conjugation system of IncHI3 plasmid MIP233
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Abstract:
The conjugation system of the IncHI3 plasmid MIP233 was studied using a transfer-derepressed Tn5-insertion mutant. The conjugative pili of this plasmid were short pointed rods resembling rigid pili, with a well-defined modal length. Unlike plasmids with rigid pili, the MIP233 mutant mediated a surface + liquid conjugation system. The pili were serologically different from all known pilus types including H pili, and did not act as receptors for any known pilus-specific bacteriophage. They converted the surface conjugation system of RP4 to a surface + liquid one. Antiserum to pili of the mutant plasmid inhibited transfer of the wild-type plasmid MIP233, demonstrating that it contained only one transfer system.
Insights
The IncHI3 plasmid MIP233 utilizes a unique conjugation system with short, rigid pili, facilitating both surface and liquid bacterial transfer. This system differs from known pili and bacteriophage interactions.
Area of Science:
- Bacterial genetics
- Molecular biology
- Plasmid biology
Background:
- The IncHI3 plasmid MIP233's conjugation system was investigated.
- A transfer-derepressed Tn5-insertion mutant was utilized for this study.
Purpose of the Study:
- To characterize the conjugative pili of the IncHI3 plasmid MIP233.
- To understand the conjugation mechanism mediated by MIP233.
- To determine the serological and phage receptor properties of MIP233 pili.
Main Methods:
- Analysis of a Tn5-insertion mutant of the IncHI3 plasmid MIP233.
- Characterization of conjugative pili morphology and length.
- Testing pili for serological relatedness to known types (e.g., H pili).
- Assessing pili as receptors for bacteriophages.
- Evaluating the effect of MIP233 pili on the conjugation system of another plasmid (RP4).
- Using antiserum against MIP233 pili to inhibit wild-type plasmid transfer.
Main Results:
- MIP233 pili are short, rigid rods with a defined length.
- The mutant mediated a surface and liquid conjugation system, unlike typical rigid pili plasmids.
- Pili were serologically distinct from known types and not receptors for known pilus-specific phages.
- MIP233 pili converted the RP4 surface conjugation system to a surface + liquid system.
- Antiserum confirmed a single transfer system in wild-type MIP233.
Conclusions:
- The IncHI3 plasmid MIP233 possesses a unique conjugation system with distinct pili.
- These pili mediate a dual surface and liquid transfer mechanism.
- The MIP233 conjugation system is independent of known pilus types and phage interactions.