The conservation of dif sequences. This figure shows the conservation quantities at each position of dif sequence in each phylum or class (Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes, α-Proteobacteria, β-Proteobacteria, γ-Proteobacteria, and δ-Proteobacteria). The black bars represent the degree of conservation in single-chromosome genomes, and the gray bars represent that of organisms harboring multiple chromosomes. The labels "XerC domain" and "XerD domain" in these graphs represent the binding sites of these proteins. The X-axis represents the nucleotide positions in the dif sequence, and the Y-axis represents the nucleotide conservation quantity. Y-axis values were normalized to percentages.