Differences in lactococcal cell wall polysaccharide structure are major determining factors in bacteriophage...

Area of Science:

• Microbiology
• Bacteriology
• Molecular Biology

Background:

• Lactococcus lactis cell wall polysaccharides (CWPS) are implicated in phage interactions.
• The precise nature of cell surface receptors for P335 and 936 phage groups remains elusive.
• Genetic variability exists within the CWPS biosynthesis operon of Lactococcus lactis.

Purpose of the Study:

• To elucidate the role of cell wall polysaccharides (CWPS) in Lactococcus lactis phage recognition.
• To characterize the structural differences in CWPS among Lactococcus lactis subtypes.
• To determine the specific CWPS structures that act as receptors for P335 and 936 phage groups.

Main Methods:

• Analysis of the CWPS biosynthesis operon in eight Lactococcus lactis strains.
• Purification and structural determination of acidic polysaccharide from L. lactis 3107 (subtype C2).
• Genetic manipulation of a subtype C1 L. lactis mutant by introducing genes from subtype C2.
• Phage challenge assays using recombinant and wild-type Lactococcus lactis strains.

Main Results:

• Five subtypes (C1-C5) of CWPS type C were identified based on genetic variability in the operon.
• The CWPS of L. lactis 3107 (subtype C2) has a distinct pentasaccharide repeating unit structure compared to subtype C1.
• Recombinant L. lactis expressing subtype C2 genes synthesized subtype C2 CWPS.
• Cell wall polysaccharides were confirmed as host receptors for tested P335 and 936 group phages.
• Differences in CWPS structure significantly influence phage host range.

Conclusions:

• Cell wall polysaccharides (CWPS) are the primary determinants of host cell surface receptor recognition for P335 and 936 group lactococcal phages.
• Structural variations in CWPS directly correlate with phage specificity and narrow host range.
• This research clarifies the molecular basis of phage-bacterial interactions, aiding in phage control strategies.