Himmelreich R, Plagens H, Hilbert H, Reiner B, Herrmann R
Zentrum für Molekulare Biologie Heidelberg, Universität Heidelberg, Germany.
Nucleic Acids Res. 1997 Feb 15;25(4):701-12. doi: 10.1093/nar/25.4.701.
The sequenced genomes of the two closely related bacteria Mycoplasma genitalium and Mycoplasma pneumoniae were compared with emphasis on genome organization and coding capacity. All the 470 proposed open reading frames (ORFs) of the smaller M.genitalium genome (580 kb) were contained in the larger genome (816 kb) of M.pneumoniae. There were some discrepancies in annotation, but inspection of the DNA sequences showed that the corresponding DNA was always present in M. pneumoniae. The two genomes could be subdivided into six segments. The order of orthologous genes was well conserved within individual segments but the order of these segments in both bacteria was different. We explain the different organization of the segments by translocation via homologous recombination. The translocations did not disturb the continuous bidirectional course of transcription in both genomes, starting at the proposed origin of replication. The additional 236 kb in M.pneumoniae,compared with theM.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 ORFs, while 76 ORFs were amplifications of ORFs existing mainly as single copies in M. genitalium. In addition, 23 ORFs containing a copy of either one of the three repetitive DNA sequences RepMP2/3, RepMP4 and RepMP5 were annotated in M.pneumoniae but not in M.genitalium,although similar DNA sequences were present. TheM.pneumoniae-specific genes included a restriction-modification system, two transport systems for carbohydrates, the complete set of three genes coding for the arginine dihydrolase pathway and 14 copies of the repetitive DNA sequence RepMP1 which were part of several different translated genes with unknown function.
对密切相关的两种细菌——生殖支原体和肺炎支原体的测序基因组进行了比较，重点在于基因组组织和编码能力。较小的生殖支原体基因组（580 kb）中所有470个提议的开放阅读框（ORF）都包含在肺炎支原体的较大基因组（816 kb）中。注释存在一些差异，但对DNA序列的检查表明，相应的DNA在肺炎支原体中总是存在的。这两个基因组可细分为六个片段。直系同源基因在各个片段内的顺序保守性良好，但两种细菌中这些片段的顺序不同。我们通过同源重组易位来解释片段的不同组织方式。这些易位并未干扰两个基因组中从提议的复制起点开始的连续双向转录过程。与生殖支原体基因组相比，肺炎支原体额外的236 kb编码了209个在生殖支原体中未鉴定出的提议ORF。在这些ORF中，110个是肺炎支原体特有的，与生殖支原体的ORF没有显著相似性，而76个ORF是生殖支原体中主要以单拷贝形式存在的ORF的扩增。此外，肺炎支原体中注释了23个含有三种重复DNA序列RepMP2/3、RepMP4和RepMP5之一拷贝的ORF，而生殖支原体中没有，尽管存在相似的DNA序列。肺炎支原体特有的基因包括一个限制修饰系统、两个碳水化合物转运系统、编码精氨酸双水解酶途径的三个基因的完整集合以及14个重复DNA序列RepMP1的拷贝，这些是几个功能未知的不同翻译基因的一部分。
