Phylogeny of the Mycoplasma mycoides cluster based on analysis of five conserved protein-coding sequences and possible implications for the taxonomy of the group.

A phylogenetic tree of the Mycoplasma mycoides cluster was inferred from a set of concatenated sequences from five housekeeping genes (fusA, glpQ, gyrB, lepA and rpoB). The relevance of this phylogeny was reinforced by detailed analysis of the congruence of the phylogenies derived from each of the five individual gene sequences. Two subclusters were distinguished. The M. mycoides subcluster comprised M. mycoides subsp. mycoides biotypes Small Colony (SC) and Large Colony (LC) and M. mycoides subsp. capri. The latter two groups could not be clearly separated, which supports previous proposals that they be united into a single taxonomic entity. The Mycoplasma capricolum subcluster included M. capricolum subsp. capricolum, M. capricolum subsp. capripneumoniae and Mycoplasma sp. bovine group 7 of Leach, a group of strains that remains unassigned. This group constituted a distinct branch within this cluster, supporting its classification as a subspecies of M. capricolum. Mycoplasma cottewii and Mycoplasma yeatsii clustered in a group that was distinct from Mycoplasma putrefaciens and they were all clearly separated from the M. mycoides cluster. In conclusion, this approach has allowed us to assign phylogenetic positions to all members of the M. mycoides cluster and related species and has proved the need to adjust the existing taxonomy. Furthermore, this method may be used as a reference technique to assign an unequivocal position to any particular strain related to this cluster and may lead to the development of new techniques for rapid species identification.