TABLE 2.
Likely spirochete synapomorphies
| Character | Comments | |
|---|---|---|
| BB0254/TP0704; RecJ single-strand nuclease protein; ∼100-amino-acid insert | Occurs just after the DHH motif of these proteins and is absent in all other bacterial RecJ proteins | |
| BB0800/TP0892; NusA zinc ribbon at the extreme C terminus | Other bacteria lack this domain (some, e.g., E. coli, have in its place a duplicated modified HhH domain) | |
| BB0132/TP0018; GreA; has a long, unique N-terminal extension | The only other bacterial genus with this extension is Chlamydia | |
| BB0512/TP0408; large protein with a signal peptide-like sequence and C-terminal HTH domain | These proteins are so far seen only in spirochetes, although smaller paralogs without the large coiled-coil region are seen in spirochetes and some other bacteria (Fig. 3b) | |
| BB0827/TP0526; plant-type HrpA helicase | Present in many bacteria and eukaryotes, but the spirochete version is closer to eukaryotic forms | |
| BB0659/TP0644; archaeal-type lysyl-tRNA synthetase | Appears to have entered the common ancestor of these spirochetes from an archaeal lineage; among other bacteria, seen only in Rickettsia | |
| BB0513, BB0514/TP0973, TP0015; archaeal-type phenylalanyl-tRNA synthetase (subunits α and β) | Appears to have entered the common ancestor of these spirochetes from an archaeal lineage | |
| BB0819/TP0342; archaeal-type cytidylate kinase | Appears to have entered the common ancestor of these spirochetes from an archaeal lineage; shares a modified P-loop with the archaeal proteins | |
| BB0020/TP0542; eukaryote-type pyrophosphate-dependent phosphofructokinase | The spirochetes are the only bacteria with this form of PFK that is otherwise seen in plants and protists | |
| BB0670/TP0364; signaling protein that contains an N-terminal CheW domain and a C-terminal protein methyltransferase domain (Fig. 3). | Domain organization unique to spirochetes | |
| BB0236/TP0421; YWTD domain proteins | Apparent horizontal transfer from animals | |
| BB0063/TP0307; membrane protein with a fusion to penicillin-binding domains similar to those found in PKN2-like protein kinases | Domain organization unique to spirochetes | |
| BB0286/TP0567; small flagellar operon protein B | Protein unique to spirochetes | |
| BB0282/TP0726; small flagellar operon protein D | Among other bacteria, only Thermotoga encodes an ortholog of this protein |