Genomic regions surrounding the orc1/cdc6.1 (A) and orc1/cdc6.2 (B) genes in the three genomes of Methanomassiliicoccales. Each homologous gene (i.e. showing more than 30% amino acid identity and an e-value < 10-5 when analyzed by blast against each other) from the 2 regions of the 3 genomes is colored differently and connected with shading. The black arrows represent genes involved in the replication process. The grey arrows represent other genes of various function with no homologue detected on the corresponding region of the 2 other genomes. “Hypoth.” refers to genes encoding hypothetical proteins.