Figure 1.

Phylogenetic relationships among the Osedax symbionts, based on the 16S rRNA gene. Additional sequences were obtained from GenBank and aligned using the ARB automated alignment tool with subsequent manual refinements. Taxa in bold denote those discussed in detail in this paper. The bacterial 16S rRNA-encoding sequences in the metagenomic sequencing reads for Osedax symbiont Rs1 were extracted using rRNASelector program. Fragments that showed overlap with an rRNA (>60 bp; HMM profile with E-value lower than 10⁻⁵) were identified as rRNA-coding regions. The 16S rRNA gene of the symbiont Rs2 sample was acquired via manual assembly of the 16S rRNA community sequence data, before metagenomic sequencing. For near full-length representatives and closest relatives, neighbor-joining analysis was conducted with Olsen distance correction. Colwellia piezophila (AB094412) was used as the outgroup. A more detailed phylogeny can be found in Salathe and Vrijenhoek (2012).