Isolation and characterization of a novel bacteriophage infecting Helicobacter pylori

Helicobacter pylori is a gram-negative gastric pathogen associated with several gastric diseases, including cancer. Although prophage sequences are frequently detected in H. pylori genomes, only a limited number of active bacteriophages infecting this species have been analyzed, leaving phage–host interactions poorly understood. Here, we isolated and characterized a novel temperate bacteriophage, 418T1, from the H. pylori strain VN0418. Transmission electron microscopy revealed that 418T1 has a spherical head with a short tail. The phage exhibited a relatively broad host range, forming plaques on 67.6% of the tested strains. Notably, 418T1 remained stable across a wide pH range (pH 3–11), consistent with gastric adaptation. Genomic analysis revealed a 30,690 bp linear double-stranded DNA genome with direct terminal repeats, consistent with a T7-like fixed-end DNA packaging mechanism. Intergenomic similarity analysis classified 418T1 as a novel species within the genus Schmidvirus . Comparative genomics identified two tail protein genes unique to 418T1. Functional characterization revealed that one of these proteins, VN33, specifically binds to H. pylori cells only after cell-surface lipopolysaccharide (LPS) depletion, suggesting that its target is masked by LPS. Our findings expand the current knowledge of H. pylori bacteriophages and provide new insights into phage–host interactions.