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Abstract:
Escherichia coli strains lysogenic for a thermoinducible Mu prophage (Mu cts62) undergo rapid lysis about 50 min after heat induction. Induction of Mu cts62 apparently causes damage to the host sequences in which Mu is inserted. The normal expression of A, BU, and X genes of Mu is needed for this specific deleterious effect on the prophage-containing host sequences. Mu deoxyribonucleic acid can be shown to reintegrate extensively at different sites on the host genome during the lytic cycle after prophage induction or after infection of sensitive cells by clear-plaque mutants of Mu. We estimate that approximately 10 copies of Mu deoxyribonucleic acid are inserted per chromosome during vegetative growth. The episome rescue method for detecting vegetative Mu deoxyribonucleic acid insertion, in which an episome is transferred from the lytically infected cells to F- receipient cells, can be applied to study Mu integration without requiring the host cells to survive. It also provides an easy system to isolate Mu insertions in transmissible episomes and plasmids.
Insights
Heat induction of Mu cts62 prophage in Escherichia coli causes host DNA damage and rapid lysis. Mu gene expression is essential for this effect, leading to extensive Mu DNA reintegration during the lytic cycle.
Area of Science:
- Bacteriology
- Molecular Biology
- Genetics
Background:
- Escherichia coli lysogenic for Mu cts62 prophage exhibit thermoinducible lysis.
- Prophage induction leads to host DNA damage and extensive Mu DNA replication and integration.
Purpose of the Study:
- To investigate the mechanism of Mu prophage-induced host DNA damage and lysis.
- To characterize the role of Mu genes in host sequence alteration.
- To analyze Mu DNA integration patterns during the lytic cycle.
Main Methods:
- Heat induction of Mu cts62 prophage in Escherichia coli.
- Analysis of host DNA damage and Mu gene expression.
- Detection of Mu DNA reintegration using episome rescue and transfer to F- recipient cells.
Main Results:
- Mu cts62 induction triggers rapid host cell lysis within 50 minutes.
- Expression of Mu A, BU, and X genes is critical for host sequence damage.
- Extensive Mu DNA reintegration occurs at multiple sites on the host genome.
- Approximately 10 copies of Mu DNA are inserted per chromosome during vegetative growth.
Conclusions:
- Mu prophage induction causes specific host DNA damage mediated by Mu gene products.
- Mu DNA undergoes extensive, multi-site integration into the host genome during its lytic cycle.
- The episome rescue method facilitates the study of Mu integration and isolation of Mu insertions.