Capsular Polysaccharide Is a Receptor of a Clostridium perfringens Bacteriophage CPS1

Area of Science:

• Microbiology
• Virology
• Bacteriophage Research

Background:

• *Clostridium perfringens* is a common cause of foodborne illness.
• Bacteriophages are promising alternatives to antibiotics for combating resistant bacteria.
• Understanding phage-host interactions is crucial for developing phage-based therapies.

Purpose of the Study:

• To isolate and characterize a virulent phage targeting *Clostridium perfringens*.
• To identify the specific host receptor used by the isolated phage CPS1 for infection.
• To elucidate the role of capsular polysaccharides in phage adsorption.

Main Methods:

• Isolation and whole-genome sequencing of the *C. perfringens* phage CPS1.
• Construction and screening of a random transposon mutant library to identify resistance genes.
• Biochemical analysis of the identified gene product and its enzymatic activities.
• Competitive inhibition assays using glucosamine and galactosamine to study phage adsorption.

Main Results:

• A virulent phage, CPS1, with a small genome and short noncontractile tail was isolated.
• The gene *CPF_0486* (encoding a protein with dual GalE and Gne activities) was identified as essential for CPS1 infection.
• Mutants lacking functional *CPF_0486* showed reduced capsular polysaccharide production.
• Glucosamine and galactosamine competitively inhibited CPS1 adsorption, indicating capsular polysaccharides are the receptor.

Conclusions:

• CPS1 belongs to the *Picovirinae* subfamily of *Podoviridae*.
• Capsular polysaccharides of *C. perfringens* serve as the primary receptor for phage CPS1.
• This finding contributes to the understanding of phage-host interactions and the development of phage therapy against *C. perfringens*.