(A) Gene context of hmdA, hmdB, and hmdC. hmdA, blue; hmdB, purple; hmdC, black. (B) Chronogram of HmdB rooted with a homolog identified in the genome of Desulfitobacterium hafniense Y51 and HmdAI rooted with HmdAII from Methanococcus maripaludis S2. The scale bar represents 0.5 substitutions per site. (C) Phylogram of representative members of the radical AdoMet superfamily of enzymes. Descriptions of the functions of the various AdoMet enzymes can be found in the work of Sofia et al. (31). The depth of the collapsed clades is proportional to the diversity of the individual enzyme class. The scale bar represents 0.6 substitutions per site.