Fig. 1.

Phylogenetic distribution of DndBCD homologs. The phylogenetic tree of DndBCD homologs in 1,349 strains was created using MEGA5.1 (41) with the maximum likelihood method and 500 bootstrap replications and was visualized using Archaeopteryx (42). Different genera are colored accordingly. The strains shaded red and green indicate that DndBCD homologs are associated with complete and incomplete DndFGH, respectively (i.e., the PT R-M and R⁻-M⁺ systems). The PT sequence contexts identified in some strains are displayed as noted.