Fig. 2

Phylogenetic tree of Candidatus Thioglobus thermophilus and related free-living and host-associated sulfur oxidizers. Ca. T. thermophilus, the thiotrophic symbiont of Bathymodiolus thermophilus, is displayed in bold. The tree was inferred from closely related 16S rRNA gene sequences obtained from the SILVA database using the SILVA Incremental Aligner (SINA) [51] and was estimated with the 16S rRNA sequence of 46 bacteria. The final alignment covered 1138 nucleotides. Sequence alignment and phylogenetic analysis were performed using the MEGA7 software tool [52]. The phylogenetic tree was constructed using the Maximum Likelihood method based on the Tamura-Nei model implemented in MEGA7 [53]. Branch bootstrap support values were calculated using 1000 replicates and are displayed as circles (black: ≥ 90%, white: ≥ 60%). For the sake of clarity some organisms were merged into groups (wedges): ^auncultured clones (KC682721, KC682765, JQ678401, AB193934); ^bwhale fall symbionts (HE814589, HE814588, HE814591 HE814585); ^cuncultured clones (FM246509, FM246513); ^duncultured clones (JQ678344, JQ678392); ^eMytilidae symbionts (AM503921, AM503923); ^fVesicomyidae symbionts (EU403432, EU403431, CP000488* 1081274–1,082,807, AP009247* 948400–949,934); ^gLucinidae symbionts (X84979, M99448, M90415); ^htube worm symbionts (NZ_AFOC01000137* 503–2033, DQ660821, NZ_AFZB01000059* 4132–5662). The lucinid clam symbionts, the vestimentiferan tube worm symbionts, and the free-living Thiomicrospira crunogena XCL-2 were included as outgroup. Branches that are not highlighted by colors represent free-living relatives. The tree is drawn to scale, with branch lengths measured in the number of substitutions per site. *these NCBI accession numbers refer to whole genome submissions and not to individually submitted 16S rRNA gene sequences (start and stop positions of the 16S rRNA gene are given after the asterisk). JdFR: Juan de Fuca Ridge, EPR: East Pacific Rise, MAR: Mid-Atlantic Ridge, OMZ: oxygen minimum zone, MFZ: Mendocino Fracture Zone, SBB: Santa Barbara Basin, WH: Woods Hole