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

Abstract

In most Gram-negative bacteria, outer membrane (OM) lipopolysaccharide (LPS) molecules carry long polysaccharide chains known as the O antigens or O polysaccharides (OPS). The OPS structure varies highly from strain to strain, with more than 188 O serotypes described in E. coli. Although many bacteriophages recognize OPS as their primary receptors, these molecules can also screen OM proteins and other OM surface receptors from direct interaction with phage receptor-binding proteins (RBP). In this review, I analyze the body of evidence indicating that most of the E. coli OPS types robustly shield cells completely, preventing phage access to the OM surface. This shield not only blocks virulent phages but also restricts the acquisition of prophages. The available data suggest that OPS-mediated OM shielding is not merely one of many mechanisms of bacterial resistance to phages. Rather, it is an omnipresent factor significantly affecting the ecology, phage–host co-evolution and other related processes in E. coli and probably in many other species of Gram-negative bacteria. The phages, in turn, evolved multiple mechanisms to break through the OPS layer. These mechanisms rely on the phage RBPs recognizing the OPS or on using alternative receptors exposed above the OPS layer. The data allow one to forward the interpretation that, regardless of the type of receptors used, primary receptor recognition is always followed by the generation of a mechanical force driving the phage tail through the OPS layer. This force may be created by molecular motors of enzymatically active tail spikes or by virion structural re-arrangements at the moment of infection.

Exploring the Bacteriophage Frontier: A Bibliometric Analysis of Clinical Trials Between 1965 and 2024

“…Overall, the analysis provides an overview of the different research areas related to bacteriophages, highlighting their potential applications in various fields, including immunology and antibacterial therapy. We found many research papers related to the topics supporting the findings of our study [21][22][23][24][25][26].…”

Large diversity in the O-chain biosynthetic cluster within populations of Pelagibacterales

“…The O-chain is a primary target for phages and might be subject to arms-race rapid evolution i.e. change much more rapidly than the rest of the genome to evade phage predation (Letarov, 2023; Mostowy and Holt, 2018). However, the data indicates that this is not achieved by swapping the whole OBC or is very rare, as only fourteen (∼7 % of the total shared OBCs) had an OBC distance that was at least half of the genomic distance, indicative of recent events ( Figure 2A ).…”