FIG. 4.

Maximum likelihood phylogenetic tree of the M components of Cbi/Nik transport systems. Genes predicted to be regulated by the nickel repressor NikR and coenzyme B₁₂ riboswitch are in blue and yellow background colors, respectively. Genomic colocalizations of cbi/nik genes with genes encoding Ni-dependent enzymes and B₁₂ biosynthesis proteins are indicated by blue and yellow dots, respectively. The color of each of the lines indicates the subunit composition of the respective nickel/cobalt transport system. Dashed lines indicate transporters containing fused M and N subunits.