Characterization of Lactococcus lactis phage antigens

Area of Science:

• Microbiology
• Molecular Biology
• Immunology

Background:

• Lactococcal phages pose significant challenges in dairy fermentation.
• Phage phi 197 is a representative of a common group of lactococcal phages with a distinct morphology.
• Developing rapid and specific phage detection methods is crucial for industrial applications.

Purpose of the Study:

• To construct fusion proteins for an immunoenzymatic phage detection test.
• To identify and characterize immunogenic epitopes of lactococcal phage phi 197.
• To map and sequence phage-specific DNA fragments encoding these epitopes.

Main Methods:

• Cloning random phage DNA fragments upstream of the lacZ gene on a plasmid vector to create fusion proteins.
• Screening recombinant plasmids for fusion protein synthesis and reaction with anti-phage antibodies.
• Mapping and sequencing phage-specific DNA fragments encoding identified epitopes.
• Raising antibodies against a specific hybrid protein to identify a minor phage protein.
• Testing antibody cross-reactivity with related phages.

Main Results:

• Fusion proteins were successfully constructed, reacting with polyclonal antibodies and conferring a Lac+ phenotype.
• Three distinct phage epitopes were identified, encoded by DNA fragments mapped to three locations on the phage genome.
• A denaturation-resistant and highly immunogenic epitope was identified from plasmid pOA17.
• This epitope is associated with a 46-kDa minor phage protein and is well-conserved in related lactococcal phages.

Conclusions:

• The identified epitope is a promising target for developing a specific and sensitive immunoenzymatic detection test for lactococcal phages.
• The developed method can be applied to detect a conserved epitope within a widespread group of lactococcal phages.
• This research contributes to improved phage control strategies in the dairy industry.