COMPARATIVE-ANALYSIS OF THE GENOMES OF THE BACTERIA MYCOPLASMA-PNEUMONIAE AND MYCOPLASMA-GENITALIUM

The sequenced genomes of the two closely related bacteria Mycoplasma g enitalium and Mycoplasma pneumoniae were compared with emphasis on gen ome organization and coding capacity, All the 470 proposed open readin g frames (ORFs) of the smaller M. genitalium genome (580 kb) were cont ained in the larger genome (816 kb) of M. pneumoniae. There were some discrepancies in annotation, but inspection of the DNA sequences showe d that the corresponding DNA was always present in M. pneumoniae, The two genomes could be subdivided into six segments, The order of orthol ogous genes was well conserved within individual segments but the orde r of these segments in both bacteria was different, We explain the dif ferent organization of the segments by translocation via homologous re combination, The translocations did not disturb the continuous bidirec tional course of transcription in both genomes, starting at the propos ed origin of replication, The additional 236 kb in M. pneumoniae, comp ared with the M. genitalium genome, were coding for 209 proposed ORFs not identified in M. genitalium, Of these ORFs, 110 were specific to M . pneumoniae exhibiting no significant similarity to M. genitalium ORF s, while 76 ORFs were amplifications of ORFs existing mainly as single copies in M. genitalium, In addition, 23 ORFs containing a copy of ei ther one of the three repetitive DNA sequences RepMP2/3, RepMP4 and Re pMP5 were annotated in M. pneumoniae but not in M. genitalium, althoug h similar DNA sequences were present, The M. pneumoniae-specific genes included a restriction-modification system, two transport systems for carbohydrates, the complete set of three genes coding for the arginin e dihydrolase pathway and 14 copies of the repetitive DNA sequence Rep MP1 which were part of several different translated genes with unknown function.