Fig. 1.

Simplified phylogeny of 3,535 Nif/Vnf/AnfH sequences. The scale bar denotes 0.1 amino acid substitutions per residue site. The solid and empty black circles denote the bootstrap supports of 90–100% and 80–89%, respectively, and the empty triangle denotes a bootstrap value of 70–79%. The outgroup is labeled by black color. The bacterial group is labeled by blue color and archaeal groups by dark red color. We use the light-independent protochlorophyllide reductase subunit L (Bch/ChlL) and chlorophyllide a reductase subunit X (BchX) sequences as the outgroup. We use the IQ-TREE method to reconstruct phylogenetic trees and ModelFinder to select the best-fit model of protein sequence evolution with ultrafast bootstrap (1,000 replicates). The model selected according to the BIC is LG + R10.