Subcellular reorganization upon phage infection reveals stepwise assembly of viral particles from membrane-associated...

Area of Science:

• Microbiology
• Structural Biology
• Virology

Background:

• Viruses are obligate intracellular parasites that hijack host cell machinery.
• Bacteriophage infection mechanisms within the crowded bacterial cytoplasm are not fully understood.
• Viral-induced compartments are crucial for genome replication and assembly.

Purpose of the Study:

• To investigate the spatial organization and viral assembly of SPP1 phage-infected bacteria.
• To elucidate the molecular mechanisms of viral replication and progeny production in situ.
• To provide comprehensive insights into the complete viral assembly pathway within a cellular context.

Main Methods:

• Electron cryo-tomography (cryo-ET) was used to visualize SPP1-infected bacteria under near-native conditions.
• High-resolution imaging allowed for the detailed observation of viral structures and cellular reorganization.
• In situ analysis provided mechanistic insights into viral DNA packaging and capsid assembly.

Main Results:

• A large viral DNA (vDNA) compartment, devoid of ribosomes and lacking a surrounding membrane or shell, was identified.
• Novel intermediates in virus assembly were observed, including procapsid precursors at the cytoplasmic membrane.
• SPP1 infection involves stepwise vDNA packaging within the compartment and subsequent capsid maturation and storage.

Conclusions:

• The study provides comprehensive mechanistic insights into the complete SPP1 viral assembly pathway directly within the bacterial cell.
• Specific steps of viral assembly are coordinated within the reorganized bacterial cytoplasm.
• The findings enhance our understanding of viral strategies for host cell manipulation and progeny production.