Phylogeny of some mycoplasmas from ruminants based on 16S rRNA sequences and definition of a new cluster within the hominis Group.
Almost complete (>96%) 16S rRNA sequences from 9 ruminant Mycoplasma were determined by solid-phase DNA sequencing. Polymorphisms were found in 4 of the 16S rRNA sequences, indicating 2 different rRNA operons. Seven polymorphisms were found in M. agalactiae, 3 in M. bovis, one in M. alkalescens, and one in M. bovirhinis. The sequence data were used to construct phylogenetic trees. All but one of the ruminant Mycoplasma sequenced in this work clustered in the hominis group. A close relationship was found between M. agalactiae and M. bovis, with a 99% nucleotide similarity between their 16S rRNA sequences. They were also found to be members of the M. lipophilum cluster of the hominis group. Furthermore, the 16S rRNA comparisons showed that M. alkalescens and M. canadense are closely related (>98.5%), and these species were found to cluster in the M. hominis cluster of the hominis group. Interestingly, M. bovirhinis grouped in a new phylogenetic cluster of the hominis group. The new cluster, which was supported by bootstrap percentage values, signature nucleotide analysis, and higher-order structural elements, was named the Mycoplasma synoviae cluster. Mycoplasma bovoculi, Mycoplasma conjunctivae, and Mycoplasma ovi-pneumoniae clustered in the Mycoplasma neurolyticum cluster of the hominis group. Mycoplasma alvi clustered with Mycoplasma pirum in the M. pneumoniae cluster of the pneumoniae group.