TY - JOUR
T1 - Cell wall glycans mediate recognition of the dairy bacterium Streptococcus thermophilus by bacteriophages
AU - Szymczak, Paula
AU - Filipe, Sérgio Raposo
AU - Covas, Gonçalo
AU - Vogensen, Finn Kvist
AU - Neves, Ana Rute
AU - Janzen, Thomas
N1 - This work is part of an Industrial PhD project funded by Innovation Fund Denmark and Chr. Hansen A/S, grant no. 4135-00104B.
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PY - 2018/12/1
Y1 - 2018/12/1
N2 - Receptors on the cell surfaces of bacterial hosts are essential during the infection cycle of bacteriophages. To date, the phage receptors of the industrial relevant dairy starter bacterium Streptococcus thermophilus remain elusive. Thus, we set out to identify cell surface structures that are involved in host recognition by dairy streptococcal phages. Five industrial S. thermophilus strains sensitive to different phages (pac type, cos type, and the new type 987), were selected to generate spontaneous bacteriophage-insensitive mutants (BIMs). Of these, approximately 50% were deselected as clustered regularly interspaced short palindromic repeat (CRISPR) mutants, while the other pool was further characterized to identify receptor mutants. On the basis of genome sequencing data, phage resistance in putative receptor mutants was attributed to nucleotide changes in genes encoding glycan biosynthetic pathways. Superresolution structured illumination microscopy was used to visualize the interactions between S. thermophilus and its phages. The phages were either regularly distributed along the cells or located at division sites of the cells. The cell wall structures mediating the latter type of phage adherence were further analyzed via phenotypic and biochemical assays. Altogether, our data suggested that phage adsorption to S. thermophilus is mediated by glycans associated with the bacterial cell surface. Specifically, the pac-type phage CHPC951 adsorbed to polysaccharides anchored to peptidoglycan, while the 987-type phage CHPC926 recognized exocellular polysaccharides associated with the cell surface.
AB - Receptors on the cell surfaces of bacterial hosts are essential during the infection cycle of bacteriophages. To date, the phage receptors of the industrial relevant dairy starter bacterium Streptococcus thermophilus remain elusive. Thus, we set out to identify cell surface structures that are involved in host recognition by dairy streptococcal phages. Five industrial S. thermophilus strains sensitive to different phages (pac type, cos type, and the new type 987), were selected to generate spontaneous bacteriophage-insensitive mutants (BIMs). Of these, approximately 50% were deselected as clustered regularly interspaced short palindromic repeat (CRISPR) mutants, while the other pool was further characterized to identify receptor mutants. On the basis of genome sequencing data, phage resistance in putative receptor mutants was attributed to nucleotide changes in genes encoding glycan biosynthetic pathways. Superresolution structured illumination microscopy was used to visualize the interactions between S. thermophilus and its phages. The phages were either regularly distributed along the cells or located at division sites of the cells. The cell wall structures mediating the latter type of phage adherence were further analyzed via phenotypic and biochemical assays. Altogether, our data suggested that phage adsorption to S. thermophilus is mediated by glycans associated with the bacterial cell surface. Specifically, the pac-type phage CHPC951 adsorbed to polysaccharides anchored to peptidoglycan, while the 987-type phage CHPC926 recognized exocellular polysaccharides associated with the cell surface.
KW - Adsorption
KW - Bacteriophages
KW - Cell wall
KW - Glycans
KW - Polysaccharides
KW - Receptors
KW - Streptococcus thermophilus
UR - http://www.scopus.com/inward/record.url?scp=85056658951&partnerID=8YFLogxK
U2 - 10.1128/AEM.01847-18
DO - 10.1128/AEM.01847-18
M3 - Article
C2 - 30242010
AN - SCOPUS:85056658951
SN - 0099-2240
VL - 84
JO - Applied and Environmental Microbiology
JF - Applied and Environmental Microbiology
IS - 23
M1 - e01847-18
ER -