The Clostridium difficile cell wall protein CwpV confers phase-variable phage resistance

Area of Science:

• Microbiology
• Bacteriophage Biology
• Host-Pathogen Interactions

Background:

• Bacteriophages (phages) are ubiquitous viruses that infect bacteria.
• Bacteria possess diverse antiphage defense mechanisms.
• Clostridium difficile is a significant human and animal pathogen.

Purpose of the Study:

• To investigate the antiphage defense mechanisms in Clostridium difficile.
• To identify bacterial host factors conferring resistance to phage infection.
• To characterize the role of the CwpV protein in Clostridium difficile antiphage immunity.

Main Methods:

• Expression of Clostridium difficile CwpV protein in bacterial cells.
• Assessing phage infection efficiency (efficiency of plating) against CwpV-expressing strains.
• Analyzing the impact of CwpV on phage adsorption and DNA replication.
• Site-directed mutagenesis to identify functional domains of CwpV.

Main Results:

• The cell-surface protein CwpV confers significant antiphage protection in Clostridium difficile.
• CwpV exhibits differential efficacy against various phage types, with siphophages being most sensitive.
• The C-terminal domain of CwpV is crucial for its antiphage activity.
• CwpV inhibits phage DNA replication but not adsorption, suggesting a superinfection exclusion-like mechanism.

Conclusions:

• CwpV represents a novel, host-encoded, phase-variable antiphage system in Clostridium difficile.
• This system provides a new avenue for understanding bacterial resistance to phages.
• The findings have implications for phage therapy and understanding C. difficile pathogenesis.