CHARACTERIZATION OF THE 16S RIBOSOMAL-RNA 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 capri ne pleuropneumonia, which is a goat disease of great global concern. S train F38 belongs to the so-called ''Mycoplasma mycoides cluster,'' an d the members of this cluster have many biochemical and serological pr operties in common, which makes it difficult to differentiate between them by conventional methods. Their phylogenetic interrelationships ar e thus uncertain. The 168 rRNA gene of the rmB operon from strain F38 was cloned and sequenced. The sequence was compared with the 168 rRNA sequences of related mycoplasmas, and phylogenetic trees were construc ted by parsimony analysis. A three-way ambiguity among strain F38, Myc oplasma capricolum, and Mycoplasma sp. strain PG50 was observed in the trees. This observation is in agreement with a recent proposal to rec lassify strain F38 and M. capricolum. A primer set was designed for in vitro amplification by PCR of a fragment of the 168 rRNA genes from t he M. mycoides cluster. The amplimers of strain F38 could be distingui shed easily from the corresponding amplimers from other members of the M. mycoides cluster by restriction enzyme analysis with PstI. This ob servation was utilized to design an identification system for strain F 38. Part of the 16S rRNA gene of the rrnA operon from strain F38 was a lso cloned, and several sequence differences between the two rRNA oper ons were discovered, revealing microheterogeneity between the two 16S rRNA genes of this organism.