CLONING THE RIBOSOMAL-RNA OPERONS OF MYCOPLASMA-FLOCCULARE AND COMPARISON WITH THOSE OF MYCOPLASMA-HYOPNEUMONIAE

In contrast to other mycoplasma species the 16S/23S rRNA and 5S rRNA operons of Mycoplasma flocculare and Mycoplasma hyopneumoniae map at least 150 kb apart (20% of the genome). Both operons from M. flocculare have been cloned and sequenced. The 23S rRNA gene sequence showed 96.7% homology with the corresponding gene of M. hyopneumoniae, equalling that found earlier for 16S rRNA and confirming the close phylogenetic relationships of these organisms. A possible upstream promoter was identified. Sequence elements upstream and downstream from each structural gene could form a stem needed for maturation of the immature rRNA transcript to mature 16S and 23S rRNA. We also identified two possible stem-and-loop sequences 3' to the 23S rRNA gene. The 5S rRNA gene itself also showed high homology with the corresponding structural gene of M. hyopneumoniae, although the upstream and downstream sequences were highly heterologous.