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Narrow-host-range IncP plasmid pHH502-1 lacks a complete IncP replication system
1Department of Genetics, University of Birmingham, UK.
Abstract:
Plasmid pHH502-1 shows incompatibility only towards members of the IncP group, but has a narrower host range than typical members of that group. In contrast to other IncP plasmids its replication was not affected by a high-copy-number plasmid carrying the replication origin (oriV) of IncP plasmid RK2. Southern blotting of pHH502-1 revealed homology to oriV, consistent with its incompatibility phenotype, but no homology to trfA, the essential replication gene of RK2. Thus it is probable that pHH502-1 does not possess a functional IncP replication system, accounting for its restricted host range. A restriction map of pHH502-1 was constructed and the mercury-resistance determinant was localized to Tn735, which also carries the trimethoprim-resistance determinant and is related to Tn21. The presence of a korB-like function on pHH502-1 was also demonstrated.
Insights
Plasmid pHH502-1 exhibits IncP incompatibility but has a limited host range due to a non-functional IncP replication system. Its mercury and trimethoprim resistance genes are located on the Tn735 transposon.
Area of Science:
- Molecular Biology
- Genetics
- Microbiology
Background:
- Plasmid pHH502-1 displays incompatibility with IncP group plasmids.
- It possesses a narrower host range compared to typical IncP plasmids.
Purpose of the Study:
- To investigate the replication mechanism and host range determinants of plasmid pHH502-1.
- To characterize the genetic elements responsible for antibiotic resistance and incompatibility.
Main Methods:
- Southern blotting to detect DNA homology.
- Restriction mapping to determine plasmid structure.
- Analysis of replication origin (oriV) and essential replication genes (trfA).
Main Results:
- pHH502-1 showed homology to oriV but not to trfA, suggesting a non-functional IncP replication system.
- The mercury and trimethoprim resistance determinants were localized to Tn735, a transposon related to Tn21.
- A korB-like function was identified on pHH502-1.
Conclusions:
- The restricted host range of pHH502-1 is likely due to its defective IncP replication system.
- Plasmid pHH502-1 carries antibiotic resistance genes on the Tn735 transposon, indicating potential for horizontal gene transfer.