Nuclease genes occupy boundaries of genetic exchange between bacteriophages

Abstract Homing endonuclease genes (HEGs) are ubiquitous selfish elements that generate targeted double-stranded DNA breaks, facilitating the recombination of HEG sequence into break site and contributing to evolutionary dynamics HEG-encoding genomes. Bacteriophages (phages) well-documented carry HEGs, with paramount characterization HEGs being focused on those encoded by coliphage T4. Recently, it has been observed highly sampled vibriophage, ICP1, is similarly enriched distinct from T4’s. Here, we examined ICP1 diverse phages, proposing HEG-driven mechanisms contribute phage evolution. Relative T4, found a variable distribution across frequently proximal or within essential genes. We identified large regions (> 10kb) high nucleotide identity flanked deemed islands, which hypothesize be mobilized activity flanking HEGs. Finally, examples domain swapping between phage-encoded other phages satellites. anticipate have larger impact trajectory than previously appreciated future work investigating role in evolution will continue highlight these observations.