Small Staphylococcus aureus plasmids are transduced as linear multimers that are formed and resolved by replicative...

Area of Science:

• Molecular Biology
• Microbiology
• Genetics

Background:

• Bacteriophages, like phi 11, can mediate generalized transduction, transferring bacterial DNA between hosts.
• Staphylococcal plasmids are extrachromosomal genetic elements crucial for bacterial adaptation and virulence.
• Understanding plasmid transduction mechanisms is vital for genetic manipulation and controlling bacterial populations.

Purpose of the Study:

• To elucidate the molecular mechanisms underlying the transduction of staphylococcal plasmids by the generalized transducing phage phi 11.
• To investigate the role of plasmid replication and phage functions in the generation of transducing particles.
• To characterize the structure and formation of high frequency transducing (Hft) particles.

Main Methods:

• Analysis of molecular processes during staphylococcal plasmid transduction by phage phi 11.
• Generation and characterization of plasmid::phage chimeras.
• Investigation of DNA replication and recombination events involved in transduction.

Main Results:

• Plasmid transduction occurs via linear concatemers requiring plasmid-initiated replication but not interplasmid recombination.
• Insertion of phage DNA fragments into plasmids dramatically increases transduction frequency, forming Hft particles.
• Hft particles contain tandem repeats of plasmid::phage chimeras, produced through active plasmid replication.

Conclusions:

• Phage functions interacting with replicating plasmid DNA likely generate concatemers.
• Homologous recombination between chimeric and phage concatemers introduces an efficient pac site, driving high-frequency transduction.
• Transduced DNA is converted to supercoiled form and then monomers, dependent on the plasmid replication system.