Figure 5

Unrooted proML tree of 35 plasmid replication initiator protein (RepA) sequences aligning with pSZ77 RepA in PSI-BLAST. The majority of RepA sequences in the tree are either from the β-Proteobacteria (blue, 15 in all) or the γ-Proteobacteria (black, 11 in all). Also represented are α-Proteobacteria (magenta) and Chlorobi (green). The SZ/KB-1 RepA (red) do not cluster with the other two δ-Proteobacteria RepA (red) suggesting a possible origin of the pSZ77 replicon region outside of the δ-Proteobacteria. Several of the RepA are chromosome-encoded, suggesting origins from mobilizable plasmids such as IncQ. The bootstrap values at each node with >90% support, 50–90% support and <50% support are indicated by black, half-shaded, and white circles, respectively. The scale bar indicates substitutions per site (0.1 = 1 in 10 amino acid residues).