FIG. 2.

Phylogeny of the Xenoturbella endosymbionts (bold) inferred from Bayesian analysis of 16S rRNA gene sequences. Scale bars, 10% sequence divergence. (A) Position of the gammaproteobacterial endosymbiont among members of the class Gammaproteobacteria based on 1,301 sequence positions between E. coli positions 58 and 1,461. (B) Position of the chlamydial endosymbiont among members of the class Chlamydiae based on 1,296 sequence positions between E. coli positions 53 and 1,466. Values are neighbor-joining-based bootstrap percentages. §, short sequence added to the tree by the parsimony method. For complete versions of the trees, see Fig. S2 in the supplemental material.