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The generation of concatemeric plasmid DNA in Bacillus subtilis as a consequence of bacteriophage SPP1 infection
1Max-Planck-Institut für Molekulare Genetik, Berlin, FRG.
Abstract:
Bacteriophage SPP1 infection of Bacillus subtilis cells bearing plasmids induces the synthesis of multigenome-length plasmid molecules. Two independent pathways can account for this synthesis. In one of those, homology to the phage genome is required, whereas in the other such homology is not a prerequisite. In wild type cells both modes overlap. In dnaB(Ts), at non permissive temperature, or in recE polA strains the main concatemeric plasmid replication mode is the homology-dependent plasmid (hdp) mode. The rate of recombination-dependent concatemeric plasmid DNA synthesis is a consequence of a phage-plasmid interaction which leads to chimeric phage::plasmid DNA. The second mode, which is an homology-independent plasmid (hip) mode seems to be triggered upon the synthesis of a phage encoded product(s) (e.g. inactivation of the exonuclease V enzyme).
Insights
Bacteriophage SPP1 infection triggers Bacillus subtilis plasmid replication through two pathways: one requiring phage genome homology and another independent of it. Both modes contribute to multigenome-length plasmid synthesis.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Bacteriophage SPP1 infects Bacillus subtilis, a common host for genetic studies.
- Plasmid replication is crucial for maintaining genetic elements within bacterial cells.
- Understanding phage-plasmid interactions is key to deciphering DNA replication and recombination mechanisms.
Purpose of the Study:
- To investigate the mechanisms by which bacteriophage SPP1 infection induces multigenome-length plasmid synthesis in Bacillus subtilis.
- To elucidate the distinct pathways involved in this induced plasmid replication.
- To characterize the roles of homology and phage-encoded factors in these pathways.
Main Methods:
- Utilizing Bacillus subtilis strains, including wild-type and mutant strains (dnaB(Ts), recE polA).
- Employing plasmid DNA and bacteriophage SPP1 for infection experiments.
- Analyzing plasmid replication modes, focusing on homology-dependent plasmid (hdp) and homology-independent plasmid (hip) pathways.
Main Results:
- Bacteriophage SPP1 infection induces multigenome-length plasmid synthesis via two pathways.
- The homology-dependent plasmid (hdp) pathway requires homology to the phage genome.
- The homology-independent plasmid (hip) pathway is triggered by phage-encoded products, potentially involving inactivation of exonuclease V.
Conclusions:
- Two distinct mechanisms, homology-dependent and homology-independent, drive plasmid concatemer formation during SPP1 infection.
- In specific mutant strains or at non-permissive temperatures, the homology-dependent pathway becomes predominant.
- Phage-plasmid interactions can lead to chimeric DNA and influence replication strategies.