N conjugative transfer system of plasmid pCU1

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• The IncN group plasmid pCU1 in Escherichia coli K-12 mediates mating and plasmid DNA transfer.
• Understanding the genetic basis of these functions is crucial for microbial genetics and biotechnology.

Purpose of the Study:

• To delineate the specific DNA region responsible for mating and DNA transfer functions of the IncN plasmid pCU1.
• To identify the genetic elements within the transfer (tra) region involved in N pilus production and phage sensitivity.

Main Methods:

• Transposon Tn5 mutagenesis was employed to analyze the pCU1 plasmid's transfer region.
• Complementation tests were performed to determine the function of different segments within the tra region.
• Deletion derivatives and molecular cloning were used to assess the minimal DNA required for specific phenotypes.

Main Results:

• A 19.4-kilobase (kb) segment of the 39-kb pCU1 plasmid specifies mating and DNA transfer functions.
• A subset of this region, comprising six complementation groups, determines sensitivity to bacteriophages IKe and PRD1 and N pilus production.
• This 19.4-kb region can be interrupted by up to 2 kb of irrelevant DNA without losing the Tra phenotype.

Conclusions:

• The 19.4-kb transfer region of the IncN plasmid pCU1 contains essential genes for pilus formation and phage sensitivity.
• Specific genetic elements within this region are sufficient for N pilus production and bacteriophage recognition.
• The findings provide insights into the genetic organization and functional domains of plasmid transfer systems.