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DNA segments of the IncX plasmid R485 determining replication and incompatibility with plasmid R6K
Abstract:
The expression of incompatibility properties between the IncX plasmids R6K and R485 of Escherichia coli was examined. For small autonomously replicating derivatives of both plasmid elements, the requirements for incompatibility expression include a functional R485 replicon and an active R6K beta-origin region. Functional R6K alpha and gamma origins are not directly involved in incompatibility expression between R6K and R485. A trans-acting replication system was constructed for plasmid R485. It consists of a 3.2-(kb) DNA fragment of R485 that specifies a product(s) in trans which supports replication from an R485 origin plasmid. A minimal R485 origin region of 591 bp was derived utilizing this trans-acting replication system and the nucleotide sequence of this origin region determined. The most striking feature of the sequence is the presence of six tandem 22-bp nucleotide sequence direct repeats.
Insights
Incompatibility between Escherichia coli IncX plasmids R6K and R485 requires a functional R485 replicon and R6K beta-origin. This study identified a minimal R485 origin with six direct repeats.
Area of Science:
- Molecular Biology
- Microbiology
- Genetics
Background:
- Incompatibility between plasmids prevents their coexistence in the same cell.
- Understanding plasmid incompatibility is crucial for molecular biology and biotechnology applications.
- The IncX plasmids R6K and R485 in Escherichia coli exhibit incompatibility properties.
Purpose of the Study:
- To investigate the molecular basis of incompatibility between IncX plasmids R6K and R485.
- To identify the specific regions and elements involved in the incompatibility phenotype.
- To characterize the minimal origin of replication for plasmid R485.
Main Methods:
- Construction of autonomously replicating derivatives of R6K and R485 plasmids.
- Analysis of incompatibility expression by monitoring plasmid coexistence.
- Development of a trans-acting replication system for R485.
- Nucleotide sequencing of the R485 origin region.
Main Results:
- Incompatibility expression requires a functional R485 replicon and the R6K beta-origin.
- R6K alpha and gamma origins are not directly involved in R6K/R485 incompatibility.
- A minimal R485 origin of 591 bp was identified.
- The minimal R485 origin contains six tandem 22-bp direct repeats.
Conclusions:
- The R6K beta-origin and R485 replicon are key determinants of incompatibility between these IncX plasmids.
- The identified R485 origin sequence provides insights into plasmid replication and incompatibility mechanisms.
- The direct repeats in the R485 origin may play a role in replication or incompatibility.