FIG 6.

Phylogeny of some genes involved in polysaccharide biosynthetic pathways. (A and B) Phylogenetic tree obtained with GalE and Glf, respectively. The trees were generated by the maximum likelihood method, and bootstrap values are indicated at each node of the tree. These genes are found only in a few number of Mollicutes, and the tree topology differs from the species tree. In the Mycoplasma mycoides cluster, galE and glf are found only in M. mycoides subsp. capri LC genomes as well as in Mycoplasma mycoides subsp. mycoides strains. Their closest homologues are found in the M. bovigenitalium genome or in the M. fermentans genome (for galE). This topology and the observation that galE and glf are not found in the other members of the Spiroplasma clade strongly suggest that these genes were acquired by M. mycoides subsp. capri LC and Mycoplasma mycoides subsp. mycoides by horizontal gene transfer from an M. bovigenitalium ancestor. (C) Phylogenetic tree obtained with manB homologues. The topology of this tree is similar to that of the species tree (see Fig. S2A in the supplemental material), except that some branches are missing. Notably, manB is found in all members of the Spiroplasma clade. The tree topology is indicative of a vertical transmission of this gene in all the Mollicutes in which it is found. It may have been deleted from the other genomes.