Figure 4.

Joint phylogenetic tree of Psu and Sid proteins. The values shown on the branches are the result of ultrafast bootstraps and show a good support for the most important nodes. The columns on the right indicate, from left to right, the Type of set (A, B or C), the variant (only shown for sets of Type B, with Type A and all Type C variants shown as white spaces) and the bacterial species. Red arrows indicate the early branching clades that correspond to cluster VII in figure 3b. Purple arrow indicates the clade corresponding to P4-like elements detected in Serratia and Yersinia bacterial hosts, that are absent in the Psu sub-tree. The Newick tree file is included as electronic supplementary material, file S5.