Prediction of leaderless mRNAs in the Epsilonproteobacteria suggests evolutionary conversion to and from leaderless mRNAs. A) The presence or absence of a leaderless mRNA can result in fusion or separation of cistrons, as shown for the leaderless cj0153c gene and the leadered H. pylori hp0553 ortholog. The dRNA-seq profiles for the cj0155c-cj0151c and hp0551-hp0555 genes show that cj0153c gene has a TSS with a σ70 -10 sequence, whereas hp0551-hp0555 is transcribed as a single multicistronic mRNA, and hp0553 has a potential ribosome binding site (RBS). The translational start site (ATG, GTG or TTG, brown), the proposed σ70 -10 sequence (red), and the proposed RBS (blue) are shown for examples from Campylobacteraceae (orange), Helicobacteraceae (pink) and other Epsilonproteobacteria (green). B) Prediction of leaderless mRNAs in the Epsilonproteobacteria, based on the sequences directly upstream of the translational start codon of 23 genes which are leaderless mRNAs in either or both C. jejuni NCTC 11168 and H. pylori 26695. The 5' UTRs were scored for the presence of gnTAnaAT or AG-rich RBS-like sequences, as shown in Figures 1C and 5A. The full set of annotated sequences and gene numbers is available in Additional file 17: Table S9. Predictions are colour-coded: yellow for of a leaderless mRNA, blue for a ribosome binding site, grey for the absence of an ortholog, and white when neither a RBS nor a suitable -10 sequence was detected. Members of the Campylobacteraceae are indicated in orange, members of the Helicobacteraceae in pink, and other Epsilonproteobacteria in green, and are ordered by the number of predicted leaderless mRNAs they have in common with C. jejuni. The genes are given at the top, with orange representing C. jejuni, pink H. pylori. A WebLogo representation of the upstream sequences and startcodons is shown for leaderless mRNAs and RBS-containing 5′ UTRs.