| Mycoplasmas (class Mollicutes) are wall-less prokaryotes, among the smallest and simplest self-replicating organisms. Most mycoplasmal rRNA genes studied have a gene order similar to other prokaryotes, i.e. 5;In this thesis, the macro-restriction maps of the genomes from two closely related porcine mycoplasma species, Mycoplasma hyopneumoniae and Mycoplasma flocculare, have been constructed using field-inversion gel electrophoresis. It has been noted that M. flocculare, like M. hyopneumoniae, has a single set of rRNA genes (16S, 23S, and 5S) and an orphan 5S rRNA gene which is separated from the closely linked 16S-23S rRNA gene cluster by at least 150 kbp.;To study the transcription regulation of the orphan 5S rRNA gene, a 665 bp Xba I fragment containing this 5S rRNA gene was cloned from M. flocculare DNA. By comparing the sequence of the M. flocculare 5S rRNA gene and its flanking regions with that of the M. hyopneumoniae 5s rRNA gene, it was found that the sizes of the 5S rRNA genes from both organisms were 106 bp with a homology of 95.3%. However, the homology of the flanking regions is very low. In the ;The physical map of the genome of M. fermentans (incognitus strain), a human mycoplasma which has attracted considerable attention recently because of its frequent isolation from AIDS patients, was constructed using field-inversion gel electrophoresis. The location of the rRNA genes (16S, 23S, and 5S) was determined on this map. The M. fermentans (incognitus strain) 980 kbp genome contained two copies of each rRNA gene (16S, 23S, and 5S). The 16S and 23S rRNA genes are each closely linked as two 16S-23S rRNA gene clusters. Both 5S rRNA genes are separated from these gene clusters. Therefore, the three rRNA genes (16S, 23S, and 5S) cannot be co-transcribed.;The results from this study indicate that comparison of the rRNA gene organization can be useful to study evolution relationship among mycoplasma species. |
