Specific Interaction of Novel Friunavirus Phages Encoding Tailspike Depolymerases with Corresponding Acinetobacter...

Area of Science:

• Microbiology
• Virology
• Biochemistry

Background:

• Acinetobacter baumannii is a critical priority nosocomial pathogen due to its increasing antibiotic resistance.
• Capsular polysaccharides (CPSs) are key virulence factors and receptors for bacteriophages infecting A. baumannii.
• Structural diversity of CPSs contributes to the pathogen's adaptability and resistance.

Purpose of the Study:

• To isolate and characterize novel bacteriophages targeting specific A. baumannii capsular types.
• To investigate the enzymatic activity and specificity of bacteriophage tailspike depolymerases (TSDs).
• To elucidate the structures of oligosaccharides resulting from CPS cleavage by TSDs.

Main Methods:

• Isolation and characterization of eight novel A. baumannii bacteriophages.
• Genomic analysis of bacteriophages, identifying them as members of the Friunavirus genus.
• Cloning, expression, and purification of TSD deletion mutants.
• Structural elucidation of oligosaccharides using NMR spectroscopy and mass spectrometry.

Main Results:

• Eight novel lytic phages targeting distinct A. baumannii capsular types (K2/K93, K32, K37, K44, K48, K87, K89, K116) were identified.
• The phages belong to the Friunavirus genus within the Autographiviridae family, with genomes ranging from 41,105-42,402 bp.
• Recombinant TSDs were shown to be glycosidases that specifically cleave A. baumannii CPSs via a hydrolytic mechanism.
• Structural analysis revealed that TSDs cleave the linkage between capsular polysaccharide repeat units (K-units).

Conclusions:

• Novel bacteriophages and their tailspike depolymerases offer specific mechanisms for targeting A. baumannii.
• The structural diversity of TSDs is crucial for phage specificity and should guide phage cocktail development.
• Understanding TSD-CPS interactions provides insights into phage therapy strategies against A. baumannii infections.