Process of infection with bacteriophage phi X174 XLI. Synthesis of defective phi X particles at 15 degrees C

Area of Science:

• Molecular Biology
• Virology
• Biochemistry

Background:

• Bacteriophage phi X174 is a small, single-stranded DNA virus.
• Viral DNA replication and assembly are complex processes.
• Understanding defective viral products can shed light on normal viral replication.

Purpose of the Study:

• To characterize the nature of single-stranded viral DNA fragments produced by phi X174-infected cells at low temperatures.
• To investigate the association of these DNA fragments with proteins.
• To determine if these structures are intermediates or end products of viral replication.

Main Methods:

• Infection of bacterial cells with bacteriophage phi X174.
• Incubation at 15 degrees C to induce DNA fragment formation.
• Analysis of cell lysates using ultracentrifugation.
• Assessment of polypeptide composition of viral particles.
• Pulse-chase experiments at 37 degrees C.

Main Results:

• Single-stranded DNA fragments, 0.2-0.9 times the size of phi X DNA, were synthesized at 15°C.
• These DNA fragments were found in heterogeneous particles (80-90S) with associated proteins.
• The protein composition of these particles was similar to mature phi X174 virions.
• Chase experiments indicated these fragments and particles are not precursors to infectious virions.

Conclusions:

• The single-stranded DNA fragments and associated 80-90S particles are defective end products of phi X174 replication at low temperatures.
• These findings suggest a potential block in viral assembly or maturation under specific conditions.
• Further research is needed to understand the precise mechanism leading to these defective particles.