Taxonomy of the Mycoplasma mycoides cluster

Some of the mycoplasmas found in diseases of ruminants, Mycoplasma capricolum, M. mycoides subsp. capri (PG3), bovine group 7 (PG50), strain F38 and strain Y goat show various degrees of relationship to M. mycoides subsp. mycoides (PG1) and to one another, such that they are referred to as the M. mycoides cluster. Studies using serology, DNA homology, isoenzyme analysis and two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) of proteins have been carried out on the type and reference strains of these organisms and some representative strains in an effort to resolve this cluster into well-defined taxa. An ad hoc committee set up by the Subcommittee on the Taxonomy of the Mollicutes examined the known data, but found that it led to conflicting opinions on the classification of the unspeciated strains, partly because of the lack of guidelines on the relative weight to be given to each criterion, and partly because insufficient strains of each member of the cluster had been examined. Although classifications were proposed, total agreement was not achieved on any one proposal, and the committee believes that decisions on the taxonomy would have to await the results of repeat tests, in which several representative strains of each of the six groups would be included with the type strain.