Fig. 6.

Phylogeny of the radical SAM domains of 1,712 NifB sequences. The scale bar denotes 0.1 amino acid substitutions per residue site. The two black circles denote the bootstrap values of 90–100% (solid circle) and 80–89% (empty circle) and the empty triangle denotes a bootstrap value of 70–79%. We use the radical SAM domains of molybdenum biosynthesis protein (MoaA) sequences as the outgroup. The outgroup is labeled by black color. The bacterial group is labeled by blue color and the archaeal groups by dark red color. We use the IQ-TREE method to reconstruct the phylogenetic tree and ModelFinder to select the best-fit model of protein sequence evolution with ultrafast bootstrap (1,000 replicates). The model selected is LG + R10.