Bacterial Virus Forcing of Bacterial O-Antigen Shields: Lessons from Coliphages.

Area of Science:

• Microbiology
• Bacteriology
• Virology

Background:

• Gram-negative bacteria possess an outer membrane (OM) with lipopolysaccharide (LPS).
• LPS includes O-antigen polysaccharides (OPS) that exhibit high strain-specific variation, with over 188 serotypes in E. coli.
• OPS can act as phage receptors but also shield OM proteins and other receptors.

Purpose of the Study:

• To review evidence on the role of E. coli O-antigen polysaccharides (OPS) in shielding bacterial cells from bacteriophages (phages).
• To analyze how OPS influences phage-host interactions, bacterial ecology, and co-evolution.
• To explore phage mechanisms for overcoming OPS-mediated resistance.

Main Methods:

• Literature review and analysis of existing data on E. coli O-antigen polysaccharides (OPS) and bacteriophage (phage) interactions.
• Examination of evidence for OPS as a primary shield against phage infection.
• Investigation of phage strategies to penetrate or bypass the OPS layer.

Main Results:

• Most E. coli OPS types effectively shield cells, preventing phage access to the OM surface.
• This shielding impacts not only virulent phages but also prophage acquisition.
• OPS-mediated shielding is a significant factor in E. coli ecology and phage-host co-evolution.

Conclusions:

• OPS-mediated OM shielding is a crucial and widespread mechanism of bacterial resistance to phages in E. coli and likely other Gram-negative bacteria.
• Phages have evolved diverse mechanisms to overcome OPS barriers, including RBP recognition of OPS or alternative receptors.
• Phage infection involves generating mechanical force to penetrate the OPS layer, via motors or structural changes.