Cellular location of Mu DNA replicas

Area of Science:

• Molecular Biology
• Virology
• Microbiology

Background:

• Bacteriophage Mu is a temperate bacteriophage that infects Escherichia coli.
• Understanding the replication and integration of bacteriophage DNA is crucial for studying viral life cycles.
• The cellular location and form of viral DNA during lytic development are key aspects of viral replication.

Purpose of the Study:

• To determine the cellular location and physical state of bacteriophage Mu DNA during its lytic cycle in Escherichia coli.
• To investigate the association of newly synthesized Mu DNA with host cell structures.

Main Methods:

• Isolation of host nucleoids from Escherichia coli lysogens at various time points after Mu prophage induction.
• Treatment of nucleoids with RNase and SDS to unfold the structure.
• Sedimentation analysis to determine the association of Mu DNA with nucleoids.
• Comparison with DNA association in induced lambda lysogens and plasmid-containing cells.

Main Results:

• Newly replicated bacteriophage Mu DNA remains associated with host cell nucleoids throughout most of the lytic cycle, even after unfolding.
• This association persists until shortly before cell lysis.
• Extrachromosomal lambda DNA also shows association with nucleoids, while plasmid DNA largely sediments independently.

Conclusions:

• Bacteriophage Mu DNA replicas are likely integrated into host chromosomes during replication.
• Accumulation of Mu DNA within the host chromosome precedes its packaging for lysis.
• The association of extrachromosomal DNA with nucleoids warrants further investigation.