OmpA and OmpC are critical host factors for bacteriophage Sf6 entry in Shigella

Abstract

Despite being essential for successful infection, the molecular cues involved in host recognition and genome transfer of viruses are not completely understood. Bacterial outer membrane proteins A and C co-purify in lipid vesicles with bacteriophage Sf6, implicating both outer membrane proteins as potential host receptors. We determined that outer membrane proteins A and C mediate Sf6 infection by dramatically increasing its rate and efficiency. We performed a combination of in vivo studies with three omp null mutants of Shigella flexneri, including classic phage plaque assays and time-lapse fluorescence microscopy to monitor genome ejection at the single virion level. Cryo-electron tomography of phage “infecting” outer membrane vesicles shows the tail needle contacting and indenting the outer membrane. Lastly, in vitro ejection studies reveal that lipopolysaccharide and outer membrane proteins are both required for Sf6 genome release. We conclude that Sf6 phage entry utilizes either outer membrane proteins A or C, with outer membrane protein A being the preferred receptor.

Conformational Changes Leading to T7 DNA Delivery upon Interaction with the Bacterial Receptor

“…In this model, a series of conformational changes is triggered sequentially. The first interaction of the virus with the outer membrane remains elusive, but studies on bacteriophages belonging to the Podoviridae family suggest that membrane proteins (probably porins) may be involved (22,23). This first interaction could be essential to facilitate subsequent recognition of the rough LPS viral receptor.…”

“…During infection, the phage is thought to interact first with a surface molecule that allows correct tail orientation relative to the bacterial envelope, followed by an irreversible interaction with the same or a different receptor; this second interaction is needed to trigger opening of the tail channel (20). Viruses that infect Gram-negative bacteria, such as Escherichia, Salmonella, Shigella, or Yersinia genus, often use lipopolysaccharide (LPS) 3 as a receptor, assisted by porins or outer membrane proteins (21)(22)(23). In the case of phage T7, the identity of the bacterial receptor that triggers the conformational changes in the tail is debated.…”

Bacteriophage Tailspikes and Bacterial O-Antigens as a Model System to Study Weak-Affinity Protein–Polysaccharide Interactions

“…10,30 The Sf6TSP analyzed in this work is a polysaccharide hydrolyzing enzyme. It recognizes and cleaves the specific O-antigen part of LPS as the first step of the bacteriophage Sf6 infection cycle in order to penetrate the protective polysaccharide coat of the bacteria and reach outer membrane receptors 31 . The bacteriophage is equipped with six TSP and hence displays 18 polysaccharide binding sites to assure multivalent fixation on the bacterial cell surface, whereas TSP hydrolysis and rebinding enable receptor search and lateral movement of the phage across the membrane LPS layer.…”

Variations in O-Antigen Biosynthesis and O-Acetylation Associated with Altered Phage Sensitivity in Escherichia coli 4s

“…For instance, phage SPC35 uses the Salmonella O12 antigen receptor, and phase-variable glucosylation of the O antigen confers transient SPC35 resistance to the bacteria (5). A temperate podovirus, Sf6, also uses O antigen of its host, Shigella flexneri, as a primary receptor (4). Interestingly, the Sf6 genome harbors the oac gene for O-antigen acetylase that causes O-serotype conversion of Sf6 lysogens, which precludes bacteriophage Sf6 adsorption to these cells (6).…”

“…The O antigen plays important and various roles in bacteriophage interactions with the host. Many bacteriophages employ the O antigen as a primary receptor that ensures reversible adsorption to the host cell followed by irreversible adsorption to a secondary receptor, most frequently an outer membrane protein (2)(3)(4). O-antigen modifications may prevent bacteriophage binding.…”