Recombination between plasmids of incompatibility groups P-1 and P-2

Area of Science:

• Molecular Biology
• Microbiology
• Genetics

Background:

• R plasmids are crucial for bacterial adaptation and antibiotic resistance.
• Incompatibility group P-2 plasmids are generally restricted to Pseudomonas hosts.
• Incompatibility group P-1 plasmids exhibit a broad host range, including Escherichia coli.

Purpose of the Study:

• To investigate the potential for recombination between P-1 and P-2 R plasmids.
• To determine if P-2 plasmids can be transferred and maintained in E. coli through recombination with P-1 plasmids.

Main Methods:

• Conjugation experiments were performed using Pseudomonas aeruginosa donor strains harboring both P-1 and P-2 plasmids and E. coli K-12 recipients.
• Selection for P-2 plasmid markers was applied to identify transconjugants.
• Characterization of transconjugant plasmids included assessing marker expression, transmissibility, incompatibility properties, phage susceptibility, and molecular weight via sucrose gradient centrifugation.

Main Results:

• P-2 plasmid markers were successfully transferred to E. coli at low frequencies when P-1 plasmids were present in the donor.
• Transconjugant plasmids expressed P-2 markers and were stably maintained and serially transmissible in E. coli, exhibiting P-1 incompatibility properties.
• Recombinant plasmids displayed characteristics of both P-1 and P-2 plasmids, including altered molecular weights and susceptibility to specific phages.
• Recombination occurred independently of the Rec gene in both donor and recipient, suggesting Rec-independent mechanisms like insertion sequence interactions.

Conclusions:

• Plasmids from different incompatibility groups, such as P-1 and P-2, can recombine, expanding their host range and genetic repertoire.
• This inter-group plasmid recombination is a significant mechanism contributing to the evolution of plasmid diversity and the spread of genetic traits, including antibiotic resistance.