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Abstract

Transposable phages (proposed family Saltoviridae) are dsDNA phages capable of generalized trans- ducon, the transfer of bacterial DNA by phages from an infected bacterium to another bacterium. Examples include the Mu and B3 phages, whose mode of acon has been described in detail at the molecular level. Despite their potenal role in mediang horizontal gene transfer between micro- biota, their known genomic diversity is limited to a small number of phages infecng a few mem- bers of Proteobacteria and Firmicutes. Here we expanded the known diversity of transposable phages. First, we idenfied transposable phage genomes in the NCBI nucleode database. Next, we dereplicated the genomes at the species level and searched for prevalent orthologous groups among their proteins. We idenfied 16 or- thologs related to 10 proteins. Using HMM profiles of those orthologs, we searched for transpos- able phages in the database of unculvated viral genomes IMG/VR and in the Gut Phage Database. Aer dereplicaon at the species level, we established a set of 635 putave transposable phages, explored their genomic diversity, reconstructed their phylogeny based on the portal protein, and ex- plored the pangenome of parcular genera associated with the human gut microbiome. The established set of putave transposable phages greatly expands the proposed Saltoviridae fam- ily from four to seven phylogenec clades. Furthermore, the expanded diversity includes phages in- fecng bacteria belonging to at least four phyla (Proteobacteria, Firmicutes, Deinococcus-Thermus, and Spirochaetes) and 47 different genera. Transposable phages were assembled from viromes de- rived from various environments, such as water, soil, and living hosts. This work significantly the known diversity and host range of transposable phages and sets the stage for further funconal characterizaon of this enigmac group of phages.