Operonization in archaeal genomes. (A) Phylogeny of 65 sequenced archaea and proportion of operon genes in each of the genomes. A species tree was constructed based on the concatenated alignments of ∼78 COGs by using FastTree (Price et al. 2010) and was retrieved from MicrobesOnline (Dehal et al. 2010). The species tree was drawn using the Interactive Tree of Life (Letunic and Bork 2007). Abbreviations for the strain names are listed in Supplemental Table S1. Four phylogenetically diverse strains which were mapped and compared by transcriptome architectures are colored in red (Pfu, Pyrococcus furiosus DSM 3638; Sso, Sulfolobus solfataricus P2; Mmp, Methanococcus maripaludis S2; Hsa, Halobacterium salinarum NRC-1). (B) Plot of optimal growth temperature [data from Prokaryotic Growth Temperature Database (Huang et al. 2004)] versus proportion of operon genes of each of 65 archaeal genomes. Color symbols denote different phyletic classes [green triangle down, Euryarchaeota—Halobacteria; yellow circle, Euryarchaeota—Methanogens (Methanobacteria, Methanococci, Methanomicrobia, and Methanopyri); blue triangle up, Euryarchaeota—hyperthermophiles (Thermococci); pink star, Crenarchaeota—Hyperthermophiles (Thermoprotei); gray diamond, Nanoarchaeota and Euryarchaeota—Archaeoglobi, Thermoplasmata]. (C) Classification of 100 conserved operons in the four extremophiles.
