Revisiting the host adhesion determinants of Streptococcus thermophilus siphophages

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