Mycoplasma pneumoniae and Mycoplasma genitalium are important causative agents of infections in humans. Like all other mycoplasmas, these species possess genomes that are significantly smaller than that of other prokaryotes. Moreover, both organisms possess an exceptionally compact set of DNA recombination and repair-associated genes. These genes, however, are sufficient to generate antigenic variation by means of homologous recombination between specific repetitive genomic elements. At the same time, these mycoplasmas have likely evolved strategies to maintain the stability and integrity of their 'minimal' genomes. Previous studies have indicated that there are considerable differences between mycoplasmas and other bacteria in the composition of their DNA recombination and repair machinery. However, the complete repertoire of activities executed by the putative recombination and repair enzymes encoded by Mycoplasma species is not yet fully understood. In this paper, we review the current knowledge on the proteins that likely form part of the DNA repair and recombination pathways of two of the most clinically relevant Mycoplasma species, M. pneumoniae and M. genitalium. The characterization of these proteins will help to define the minimal enzymatic requirements for creating bacterial genetic diversity (antigenic variation) on the one hand, while maintaining genomic integrity on the other.

中文翻译：

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肺炎支原体和生殖支原体抗原变异和基因组完整性维持的机制

肺炎支原体和生殖支原体是人类感染的重要病原体。像所有其他支原体一样，这些物种的基因组明显小于其他原核生物的基因组。此外，这两种生物都拥有一组异常紧凑的 DNA 重组和修复相关基因。然而，这些基因足以通过特定重复基因组元件之间的同源重组产生抗原变异。与此同时，这些支原体可能已经进化出策略来维持其“最小”基因组的稳定性和完整性。先前的研究表明，支原体与其他细菌在 DNA 重组和修复机制的组成上存在相当大的差异。然而，由支原体物种编码的推定重组和修复酶所执行的全部活动尚未完全了解。在本文中，我们回顾了目前关于可能构成两种最临床相关的支原体物种肺炎支原体和生殖支原体 DNA 修复和重组途径一部分的蛋白质的知识。一方面，对这些蛋白质的表征将有助于确定产生细菌遗传多样性（抗原变异）的最低酶促要求，另一方面又保持基因组完整性。我们回顾了目前关于可能构成两种最临床相关的支原体物种肺炎支原体和生殖支原体 DNA 修复和重组途径一部分的蛋白质的知识。一方面，对这些蛋白质的表征将有助于确定产生细菌遗传多样性（抗原变异）的最低酶促要求，另一方面又保持基因组完整性。我们回顾了目前关于可能构成两种最临床相关的支原体物种肺炎支原体和生殖支原体 DNA 修复和重组途径一部分的蛋白质的知识。一方面，对这些蛋白质的表征将有助于确定产生细菌遗传多样性（抗原变异）的最低酶促要求，另一方面又保持基因组完整性。