Mechanisms responsible for a PhiX174 mutant's ability to infect Escherichia coli by phosphorylation

Area of Science:

• Virology
• Microbiology
• Molecular Biology

Background:

• Viral host range expansion is crucial for understanding virus-host interactions.
• The PhiX174 bacteriophage typically infects Escherichia coli C, requiring specific lipopolysaccharide (LPS) for entry.
• Understanding the mechanisms of viral entry is key to controlling viral infections and evolution.

Purpose of the Study:

• To investigate the genetic and molecular basis for the expanded host range of the PhiX174 bacteriophage mutant JACS-K.
• To identify the specific viral changes that enable infection of bacterial strains lacking the native lipopolysaccharide (LPS) receptor.
• To elucidate the role of virion surface modifications in overcoming host specificity barriers.

Main Methods:

• Comparative analysis of PhiX174 bacteriophage strains (wild-type and JACS-K).
• Bacterial infection assays using Escherichia coli C and Escherichia coli K-12.
• Genetic sequencing and protein analysis to identify mutations in the JACS-K strain.

Main Results:

• The PhiX174 mutant JACS-K demonstrated an expanded host range, successfully infecting both Escherichia coli C and Escherichia coli K-12.
• Escherichia coli K-12 lacks the specific lipopolysaccharide (LPS) typically required for PhiX174 wild-type infection.
• A single amino acid conversion from alanine to threonine on the JACS-K virion surface was identified as the key mutation responsible for the altered host range.

Conclusions:

• The mutation conferring an alanine to threonine change on the virion surface is directly responsible for the expanded host range of PhiX174 JACS-K.
• This finding highlights the critical role of specific viral surface proteins and their modifications in determining viral tropism and host specificity.
• The study provides insights into viral adaptation mechanisms and the potential for bacteriophages to overcome host immune defenses or receptor limitations.