Multilocus sequence typing scheme for the characterization of 936-like phages infecting Lactococcus lactis

Area of Science:

• Dairy Microbiology
• Bacteriophage Genomics
• Molecular Typing

Background:

• Lactococcus lactis phage infections pose significant economic threats to the dairy industry by disrupting fermentation and compromising product safety.
• Emergence of new virulent phages necessitates rapid identification methods for effective antiphage strategies.

Purpose of the Study:

• To develop and validate a multilocus sequence typing (MLST) scheme for characterizing 936-like phages, the predominant group infecting L. lactis.
• To establish a standardized method for routine phage identification within dairy processing environments.

Main Methods:

• Targeted five conserved genomic regions (packaging, morphogenesis, lysis modules) for MLST analysis.
• Analyzed 100 phages from diverse geographical origins (1971-2010) using PCR and sequence analysis.
• Compared MLST data with Restriction Fragment Length Polymorphism (RFLP) patterns.

Main Results:

• The MLST scheme demonstrated high discriminatory power, identifying 93 distinct sequence types among the 100 phages analyzed.
• The lys gene locus (endolysin) was most discriminative (65 alleles), while the mcp gene locus (major capsid protein) was most conserved (54 alleles).
• Phylogenetic analysis revealed strong correlation between sequence types and phage host range, suggesting clonal evolution.

Conclusions:

• The developed MLST scheme provides an efficient and highly discriminative tool for characterizing 936-like Lactococcus lactis phages.
• This method facilitates rapid identification of emerging phages, enabling timely adaptation of control measures in the dairy industry.
• A public database for the MLST system is available at http://pubmlst.org/bacteriophages/ for broader research use.