biostudies-literatureUnknown11(18)Byers SMHBacteriophages (phages) are viruses that can kill bacteria, thereby editing and shaping microbial communities. The telomere phages are a curious form using telomere-like structures to replicate their genomes as linear extrachromosomal elements. Here, we find that telomere phages are widely distributed in bacteria, being highly prevalent in <i>Klebsiella</i> species. We establish a model system to investigate telomere phage biology by isolating the virions of telomere phages and infecting naïve strains to create isogenic lines with and without a phage. We find that only a small set of telomere phage proteins is expressed in phage-host cells, including a toxin-the telocin-that kills other <i>Klebsiella</i> strains. We identify and validate a set of telocins in the genomes of other prevalent Science advanceseadt1627https://www.ebi.ac.uk/biostudies/studies/S-EPMC12042878biostudies-literatureTelomere bacteriophages are widespread and equip their bacterial hosts with potent interbacterial weapons.PMC12042878Rocker ALithgow TShort FLTan KSByers SMHSteele JRRosas NCLi YTaiaroa GSchittenhelm RBDunstan RAWilksch JJNguyen TNTfalseTelomere bacteriophages are widespread and equip their bacterial hosts with potent interbacterial weapons.Bacteriophages (phages) are viruses that can kill bacteria, thereby editing and shaping microbial communities. The telomere phages are a curious form using telomere-like structures to replicate their genomes as linear extrachromosomal elements. Here, we find that telomere phages are widely distributed in bacteria, being highly prevalent in <i>Klebsiella</i> species. We establish a model system to investigate telomere phage biology by isolating the virions of telomere phages and infecting naïve strains to create isogenic lines with and without a phage. We find that only a small set of telomere phage proteins is expressed in phage-host cells, including a toxin-the telocin-that kills other <i>Klebsiella</i> strains. We identify and validate a set of telocins in the genomes of other prevalent 2025-01-01T00:00:00Z2025 May2026-06-03T02:42:30.37Z2025-07-06T03:06:00.694ZS-EPMC120428784030561410.1126/sciadv.adt1627