“…(b) Previously published unrooted phylogeny of 6,779 RNR α sequences. 3 Host organisms of structurally characterized RNRs are shown in circles. In clockwise order, class I: Fj, Flavobacterium johnsoniae; Au, Actinobacillus ureae; Ec, Escherichia coli ; Ng, Neisseria gonorrhea; Bs, Bacillus subtilis; St: Salmonella typhimurium; Aa, Aquifex aeolicus; Pa, Pseudomonas aeruginosa ; Sc, Saccharomyces cerevisiae; Hs, Homo sapiens ; class II: Ll, Lactobacillus leichmannii; Tm, Thermotoga maritima; Rs, Rhodobacter sphaeroides ; and class III: T4 , Bacteriophage T4; Tm, Thermotoga maritima .…”