Characterization of the 16S rRNA genes from Mycoplasma sp. strain F38 and development of an identification system based on PCR.

Mycoplasma sp. (strain F38) is the causative agent of contagious caprine pleuropneumonia, which is a goat disease of great global concern. Strain F38 belongs to the so-called "Mycoplasma mycoides cluster," and the members of this cluster have many biochemical and serological properties in common, which makes it difficult to differentiate between them by conventional methods. Their phylogenetic interrelationship are thus uncertain. The 16S rRNA gene of the rrnB operon from strain F38 was cloned and sequenced. The sequence was compared with the 16S rRNA sequences of related mycoplasmas, and phylogenetic trees were constructed by parsimony analysis. A three-way ambiguity among strain F38, Mycoplasma capricolum, and Mycoplasma sp. strain PG50 was observed in the trees. This observation is in agreement with a recent proposal to reclassify strain F38 and M. capricolum. A primer set was designed for in vitro amplification by PCR of a fragment of the 16S rRNA genes from the M. mycoides cluster. The amplimers of strain F38 could be distinguished easily from the corresponding amplimers from other members of the M. mycoides cluster by restriction enzyme analysis with PstI. This observation was utilized to design an identification system for strain F38. Part of the 16S rRNA gene of the rrnA operon from strain F38 was also cloned, and several sequence differences between the two rRNA operons were discovered, revealing microheterogeneity between the two 16S rRNA genes of this organism.