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Co-evolution of a filamentous bacteriophage and its defective interfering particles
Abstract:
Serial passage of bacteriophage f1 at high multiplicities of infection results in the appearance of defective deletion mutants (miniphage) that harbor a tandem reiteration of regions of the f1 genome near the origin of DNA replication. These miniphage interfere with the growth of wild-type f1, and cause a sharp decrease of the viable phage titer. Upon further passage, however, the titer increases again. Viable phage variants (maxiphage) appear which harbor the same tandem reiteration of DNA as the miniphage. The maxiphage are more resistant than the wild type to interference by the miniphage. In the absence of miniphage the maxiphage grow at the same rate as the wild type. The structure of the DNA reiteration gradually changes during further passage. Miniphage and maxiphage follow, in parallel, a similar course of changes in the pattern of reiteration. In miniphage the reiterations change while the deletions are conserved. Serial passage of maxiphage quickly yields miniphage, which harbor a reiteration identical to that of the parental maxiphage. Both reiteration and deletion are relevant to the mechanism of interference by miniphage. Thus serial passage of the filamentous phage affords an experimental system to study evolution of a DNA genome in test tubes. Possible mechanisms of the interference by miniphage are discussed.
Insights
Serial passage of bacteriophage f1 creates defective mutants (miniphage) that hinder wild-type growth. Further passage yields resistant variants (maxiphage), offering insights into viral genome evolution.
Area of Science:
- Molecular Biology
- Virology
- Evolutionary Biology
Background:
- Bacteriophage f1 undergoes genetic changes during serial passage.
- High multiplicities of infection can lead to defective phage mutants.
Purpose of the Study:
- To investigate the genetic alterations in bacteriophage f1 during serial passage.
- To understand the interference mechanisms between wild-type phage and defective mutants.
Main Methods:
- Serial passage of bacteriophage f1 at high multiplicities of infection.
- Analysis of DNA structures in miniphage and maxiphage variants.
- Monitoring phage titer and growth rates.
Main Results:
- Defective deletion mutants (miniphage) with tandem DNA reiterations appeared.
- Viable variants (maxiphage) with similar reiterations emerged, showing resistance to miniphage interference.
- Both miniphage and maxiphage exhibited parallel changes in DNA reiteration patterns during passage.
Conclusions:
- Tandem DNA reiteration and deletions are crucial for miniphage interference.
- Serial passage of filamentous phage provides a model for studying DNA genome evolution in vitro.
- The study elucidates mechanisms of phage-host interactions and viral adaptation.