Supplementary Figure S1.
The phylogenetic tree obtained in MrBayes for the HmuY homologs from all phyla. Main bacterial lineages are marked in different colors. Eleven main groups can be recognized in the phylogenetic tree. Three big groups (G1, G3 and G5) are dominated by Bacteroidetes sequences representing various classes of this phylum: Bacteroidia, Chitinophagia, Cytophagia, Flavobacteriia, Saprospiria and Sphingobacteriia. P. gingivalis HmuY and T. forsythia Tfo are placed within the G3 clade among other Bacteroidia sequences. Groups G9 and G10 include almost exclusively Proteobacteria representatives and are placed close to group G11 including Euryarchaeota sequences and one α-proteobacterium. A monophyletic group is G7, which contains representatives of Spirochaetes. Potential horizontal gene transfers occurred likely from Euryarchaeota to a Rhizobiales bacterium (G11), from d-Proteobacteria to two Spirochaeta species (G8), from Bacteroidetes to cyanobacterium Lyngbya confervoides (G6) and cyanobacterium Hassallia byssoidea (G5) as well as from Bacteroidetes to a Verrucomicrobia bacterium, an Euryarchaeota archaeon and a γ-proteobacterium (G1). In these cases one or few sequences from one phylum are significantly clustered within many sequences of the other distantly related phylum. The full tree with support values obtained by various methods is presented in Supplementary Figure S2.