Genomic features of ribosomal genes in Euryarchaeota. (A) Phylogeny of Euryarchaeota highlighting the position of the Methanomassiliicoccales (according to ). The seven orders of methanogens are in red. (B) Genomic organization of ribosomal genes in Euryarchaeota: 5S, 16S and 23S rRNA genes are symbolized by blue, green and orange arrows, respectively. They are indicated irrespectively of the (+) or (-) DNA strand carrying them. A plain line defines an operon organization where tRNAs (when present) are not shown, nor the number of genes encoding rRNA with the exception of the Methanomassiliicoccales. The 5S rRNA gene in bracket refers to a second 5S rRNA copy isolated from the 16S-23S-5S rRNA gene operon in Methanococcus maripaludis C5.