Bacteria have numerous distinctive groups of phage–plasmids with conserved phage and variable plasmid gene repertoires

Abstract Plasmids and temperate phages are key contributors to bacterial evolution. They usually regarded as very distinct. However, some elements, termed phage–plasmids, known be both plasmids phages, e.g. P1, N15 or SSU5. The number, distribution, relatedness characteristics of these phage–plasmids poorly known. Here, we screened for elements among ca. 2500 12000 identified 780 across diverse phyla. We grouped 92% them by similarity gene repertoires eight defined groups 18 other broader communities elements. existence large suggests that ancient. Their large, the average element is larger than an phage plasmid, they include slightly more homologs plasmids. analyzed pangenomes genetic organization each group found genes conserved co-localized within distinct groups, whereas with in much variable most accessory genes. Phage–plasmids a sizeable fraction sequenced (?7%) (?5%), could have roles bridging divide between mobile