Comparative genomics of the Epsilonproteobacteria highlights a lack of gene order-based genome synteny throughout this lineage. A) Phylogenetic tree of 42 members of the Epsilonproteobacteria, based on comparison of 16S rDNA sequences. Members of the Campylobacteraceae (the genera Campylobacter, Sulfurospirillum (Sulfsp) and Arcobacter (Arcob)) are highlighted in orange, members of the Helicobacteraceae are highlighted in pink (the genera Helicobacter, Wolinella, Sulfurimonas (Sm) and Sulfuricurvum (Scu)), and other Epsilonproteobacteria are highlighted in green (the genera Nitratifractor (Nitfr), Sulfurovum, Nitratiruptor, Caminibacter (Camin) and Nautilia (Naut)). Sulfurovum sp. AR is not included in this tree as a full 16S rDNA sequence was not available from the genome sequence. B) Selected scatter plots of gene order-based genome synteny comparisons of C. jejuni NCTC 11168 with other members of the Campylobacteraceae, and H. pylori 26695 with other members of the Helicobacteraceae. The full comparisons are shown in Additional file 15: Figure S8, full information is given in Additional file 16: Table S8. Both the Campylobacteraceae and Helicobacteraceae show a rapid loss of genome synteny, even within the species Campylobacter and Helicobacter.