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Participation of the lytic replicon in bacteriophage P1 plasmid maintenance

M B Yarmolinsky1, E B Hansen, S Jafri

  • 1Laboratory of Biochemistry, National Cancer Institute, Bethesda, Maryland 20892.

Journal of Bacteriology
|September 1, 1989
PubMed

Insights

The P1 bacteriophage uses both a plasmid and a viral lytic replicon for replication. Even when the plasmid replicon is blocked, the viral lytic replicon ensures continued, albeit slower, P1 phage replication.

Area of Science:

  • Molecular Biology
  • Virology
  • Genetics

Background:

  • P1 bacteriophage replication relies on two main replicons: a plasmid replicon and a viral lytic replicon.
  • The plasmid replicon's stable, low-copy-number maintenance suggested it was the primary driver of P1 prophage replication.

Purpose of the Study:

  • To investigate the role of the viral lytic replicon in P1 bacteriophage prophage replication.
  • To determine if the lytic replicon contributes to replication when the plasmid replicon is inhibited.

Main Methods:

  • Experimental prevention of replication from the P1 plasmid replicon.
  • Analysis of prophage replication rates in the absence of plasmid replicon activity.
  • Comparison of replication in wild-type P1 and thermoinducible P1 c1.100 lysogens.

Main Results:

  • Prophage replication persisted even when the plasmid replicon's function was inhibited.
  • Residual replication was attributed to incomplete repression of the lytic replicon by the c1 immunity repressor.
  • P1 c1.100 lysogens showed significant replication at 32°C when the plasmid replicon was non-functional, with an elevated plasmid copy number.

Conclusions:

  • The P1 viral lytic replicon can independently drive prophage replication, supplementing the plasmid replicon.
  • Incomplete repression of the lytic replicon by the c1 repressor contributes to P1 plasmid maintenance.
  • The lytic replicon's auxiliary role enhances the stability of the P1 plasmid prophage.

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