Classification of the Type 1 bacteriophages. (A) Tree representation of Type 1 phage similarities, built from a hierarchical agglomerative clustering procedure applied to a matrix of similarity scores between pairs of phages (combining HHsearch probabilities and percentage of identity) and represented using the ETE2 library . The different branches of the tree were sorted into 10 Clusters, highlighted by different background colors. Phage names labelled by black circles filled in grey indicate the Myoviridae phages. Bacterial hosts of the phages are indicated in the bottom for each Cluster with the same color code as in the classification tree, in order to highlight the consistency between the Cluster and host phyla. (B) Gene organisation of a representative phage of each Cluster. A more complete view of gene organisation sorted by Clusters is presented on the Virfam webserver, in order to highlight the consistency between the Cluster and neck gene order distributions.