A comparative genomics approach for identifying host-range determinants in Streptococcus thermophilus bacteriophages

Area of Science:

• Microbiology
• Genomics
• Bacteriology

Background:

• Phages infecting Streptococcus thermophilus pose significant challenges to dairy fermentations.
• Understanding phage-host interactions is key to managing these threats.

Purpose of the Study:

• To explore the genetic diversity of S. thermophilus phages.
• To identify genetic determinants, specifically receptor binding proteins (RBPs), linked to host specificity.
• To correlate phage RBP genotypes with bacterial receptor genotypes.

Main Methods:

• Comparative genomic analysis of 142 S. thermophilus phage genomes.
• Phylogenetic analysis of core genomes and receptor binding proteins (RBPs).
• Experimental confirmation of RBP role in host recognition using fluorescently labeled RBP.

Main Results:

• Phylogenetic analysis revealed distinct groups of S. thermophilus phages (cos, pac, 5093, 987).
• Phage host range correlated with core genome and RBP phylogeny.
• RBP binding to host strains was experimentally confirmed.
• RBP phylogeny within the cos group correlated with the host's exocellular polysaccharide operon genotype.

Conclusions:

• Receptor binding proteins (RBPs) are significant determinants of host specificity in S. thermophilus phages.
• The RBP genotype is linked to the host's exopolysaccharide operon, providing a basis for host recognition.
• These findings offer insights for developing strategies to control phage infections in dairy production.