title: Spontaneous and transient defence against bacteriophage by phase-variable glucosylation of O-antigen in Salmonella enterica serovar Typhimurium.
abstract: As natural killers of bacteria, bacteriophages have forced bacteria to develop a variety of defence mechanisms. The alteration of host receptors is one of the most common bacterial defence strategies against phage infection, which completely blocks phage attachment but comes at a potential fitness cost to the bacteria. Here, we report the cost-free, transient emergence of phage resistance in Salmonella enterica subspecies enterica serovar Typhimurium through a phase-variable modification of the O-antigen. Phage SPC35 typically requires BtuB as a host receptor but also uses the Salmonella O12-antigen as an adsorption-assisting apparatus for the successful infection of S. Typhimurium. The α-1,4-glucosylation of galactose residues in the O12-antigen by phase variably expressed O-antigen glucosylating genes, designated the (LT)             (2)  gtrABC1 cluster, blocks the adsorption-assisting function of the O12-antigen. Consequently, it confers transient SPC35 resistance to Salmonella without any mutations to the btuB gene. This temporal switch-off of phage adsorption through phase-variable antigenic modification may be widespread among Gram-negative bacteria-phage systems.
authors.affiliation: Department of Food and Animal Biotechnology, Seoul, Korea.
authors.forename: Minsik
authors.initials: M
authors.lastname: Kim
authors.forename: Sangryeol
authors.initials: S
authors.lastname: Ryu
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001435:Bacteriophages / Q000502:physiology*; D006031:Glycosylation; D019081:O Antigens / Q000235:genetics / Q000378:metabolism*; D011991:Receptors, Virus / Q000235:genetics / Q000378:metabolism*; D012486:Salmonella typhimurium / Q000235:genetics / Q000378:metabolism* / Q000821:virology*; D053585:Virus Attachment
chemical_list: D001426:Bacterial Proteins; D019081:O Antigens; D011991:Receptors, Virus