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A natural mutant of plasmid RP4 that confers phage resistance and reduced conjugative transfer
L B Kornstein1, V L Waters, R C Cooper
1Sanitary Engineering and Environmental Health Research Laboratory, University of California, Berkeley.
Abstract:
A natural isolate of RP4 (PRC#116) acquired from the Stanford University Plasmid Reference Center differed from the wild-type Incompatibility Group P plasmid in several respects. Cells of Escherichia coli harboring PRC#116 were resistant to the IncP pili-specific bacteriophage PRD1 and GU5, and transferred this plasmid at a lower efficiency than the wild-type RP4. Phage sensitivity was restored, and transfer considerably improved in PRC#116+ bacteria transformed with plasmid constructs containing the origin of transfer (oriT region) of RP4. Mutant RP4 plasmids equivalent to PRC#116 were selected at a high frequency from an RP4+ E. coli population infected with PRD1 indicating that this RP4 variant may be the product of a very common mutation of the wild-type plasmid.
Insights
A natural plasmid isolate (PRC#116) showed resistance to specific bacteriophages and reduced transfer efficiency compared to wild-type RP4. Restoring the origin of transfer region improved these traits, suggesting a common mutation in the plasmid.
Area of Science:
- * Molecular Biology
- * Microbiology
- * Genetics
Background:
- * The Incompatibility Group P (IncP) plasmid RP4 is a well-characterized conjugative plasmid.
- * Natural plasmid variants can arise through mutations affecting plasmid function and host interactions.
Purpose of the Study:
- * To characterize a natural isolate of RP4 (PRC#116) and compare its properties to the wild-type.
- * To investigate the genetic basis for the observed differences in phage resistance and transfer efficiency.
Main Methods:
- * Phenotypic characterization of Escherichia coli strains harboring PRC#116 and wild-type RP4.
- * Bacteriophage sensitivity assays using PRD1 and GU5.
- * Plasmid transfer efficiency measurements.
- * Complementation experiments using plasmid constructs with the RP4 origin of transfer (oriT region).
Main Results:
- * The natural isolate PRC#116 conferred resistance to bacteriophages PRD1 and GU5 in E. coli.
- * PRC#116 exhibited significantly lower plasmid transfer efficiency compared to wild-type RP4.
- * Introduction of the RP4 oriT region into PRC#116 restored phage sensitivity and improved transfer efficiency.
Conclusions:
- * The natural isolate PRC#116 possesses altered characteristics, including phage resistance and reduced transfer efficiency.
- * The origin of transfer region is implicated in the observed phenotypic differences.
- * The high frequency of selecting PRC#116-like mutants suggests a common mutational pathway in RP4.