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Bacteriophages (or phages) represent a persistent threat to the success and reliability of food fermentation processes. Recent reports of phages that infect Streptococcus thermophilus have highlighted the diversification of phages of this species. Phages of S. thermophilus typically exhibit a narrow range, a feature that is suggestive of diverse receptor moieties being presented on the cell surface of the host. Cell wall polysaccharides, including rhamnose-glucose polysaccharides and exopolysaccharides have been implicated as being involved in the initial interactions with several phages of this species. Following internalization of the phage genome, the host presents several defences, including CRISPR-Cas and restriction and modification systems to limit phage proliferation. This review provides a current and holistic view of the interactions of phages and their S. thermophilus host cells and how this has influenced the diversity and evolution of both entities. [ABSTRACT FROM AUTHOR]

Summary: Available 3D structures of bacteriophage modules combined with predictive bioinformatic algorithms enabled the identification of adhesion modules in 57 siphophages infecting Streptococcus thermophilus (St). We identified several carbohydrate‐binding modules (CBMs) in so‐called evolved distal tail (Dit) and tail‐associated lysozyme (Tal) proteins of St phage baseplates. We examined the open reading frame (ORF) downstream of the Tal‐encoding ORF and uncovered the presence of a putative p2‐like receptor‐binding protein (RBP). A 21 Å resolution electron microscopy structure of the baseplate of cos‐phage STP1 revealed the presence of six elongated electron densities, surrounding the core of the baseplate, that harbour the p2‐like RBPs at their tip. To verify the functionality of these modules, we expressed GFP‐ or mCherry‐coupled Tal and putative RBP CBMs and observed by fluorescence microscopy that both modules bind to their corresponding St host, the putative RBP CBM with higher affinity than the Tal‐associated one. The large number of CBM functional domains in St phages suggests that they play a contributory role in the infection process, a feature that we previously described in lactococcal phages and beyond, possibly representing a universal feature of the siphophage host‐recognition apparatus. [ABSTRACT FROM AUTHOR]