BldB and Hpb phylogenies. Maximum likelihood trees constructed from amino acid sequences of BldB homologs (left) and Hpb homologs (right). Sequence names indicate strain identity via locus tags. Values on edges represent SH-based local support values. The branch length represents evolutionary distance using the Gamma20 model within FastTree 2 . Additional length is given to some branches with dashed lines to allow room for bootstrap values. Adjacent bldB and hpb genes are indicated in the two trees by numbered boxes to the right of the trees. Not all occurrences of bldB or hpb are accompanied by the other gene, as is the case with bldB originally characterized from Streptomyces griseus NBRC 13350 (SGR_1796.BldB). Box 7, highlighted in red, indicates incongruence between bldB and corresponding hpb gene phylogeny suggesting horizontal acquisition or gene conversion at one of these loci. Boxes 12.1 and 12.2, highlighted in blue, show an instance where bldB was duplicated locally without accompanying duplication of hpb.