The fate of phage lambda DNA in lambda-infected minicells

Area of Science:

• Microbiology
• Molecular Biology
• Virology

Background:

• Bacteriophage lambda is a model virus extensively studied in molecular biology.
• Escherichia coli minicells are small, anucleate derivatives of E. coli used to study surface phenomena and gene expression.
• ColE1 is a well-characterized plasmid in E. coli, essential for understanding plasmid-host interactions.

Purpose of the Study:

• To investigate the fate of bacteriophage lambda DNA within Escherichia coli minicells.
• To determine the impact of phage lambda infection on ColE1 plasmid DNA synthesis.
• To characterize the initial synthesis and structural state of lambda DNA post-infection in minicells.

Main Methods:

• Infection of E. coli minicells (both plasmid-free and ColE1-harboring) with bacteriophage lambda.
• Analysis of lambda DNA binding to the minicell membrane.
• Assessment of DNA synthesis using radiolabeling techniques.
• Characterization of DNA structures (e.g., supercoiling).

Main Results:

• Demonstrated binding of lambda DNA to the minicell membrane.
• Confirmed the formation of supercoiled, covalently-closed circular lambda DNA structures.
• Observed a complete abolition of ColE1 plasmid DNA synthesis upon phage infection.
• Detected only slight, non-replicative synthesis of lambda DNA fragments shortly after infection.

Conclusions:

• Phage lambda DNA interacts with the E. coli minicell membrane, adopting a supercoiled form.
• Lambda infection effectively inhibits host plasmid replication.
• Early lambda DNA synthesis is limited and associated with fragmented DNA, suggesting a non-replicative process.