Section of Infectious Diseases, Department of Medicine, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA.
Mycoplasma Laboratory, Statens Serum Institut, Copenhagen, Denmark.
J Med Microbiol. 2012 Feb;61(Pt 2):191-197. doi: 10.1099/jmm.0.030858-0. Epub 2011 Oct 13.
Mycoplasma genitalium, a human pathogen associated with sexually transmitted diseases, is unique in that it has the smallest genome of any known free-living organism. Despite its small genome, 4.7 % of the total genomic sequence is devoted to making the MgPa adhesin operon (containing the MG190, MG191 and MG192 genes) and its repetitive chromosomal sequences (known as MgPars). The goals of this study were to investigate the location, organization and variability of trinucleotide tandem repeats (TTRs) in the MgPa operon and MgPars and to explore the possible mechanisms and role of TTR variations. By analysing the complete MgPa operon and complete or partial MgPar sequences in a collection of 15 geographically diverse clinical strains of M. genitalium, TTR sequences were identified in four regions in MG191, one region in MG192, and two or three regions in each of all nine MgPars except for MgPar 3. These TTRs were variable not only in the repeat copy number but also in the repeat unit sequence among or within strains. The key mechanisms for the TTR variations likely include recombination between MgPa and MgPars, and slipped-strand mispairing. TTR variation may represent a mechanism to maximize the variation of the MgPa operon, which is complementary to genetic variation involving segmental recombination between MgPa and MgPars, thus enhancing the organism's ability to adhere to and colonize host cells as well as evasion of the host immune system.
生殖道支原体，一种与性传播疾病相关的人类病原体，其独特之处在于它拥有所有已知自由生活生物体中最小的基因组。尽管基因组很小，但总基因组序列的 4.7%用于制造 MgPa 黏附素操纵子（包含 MG190、MG191 和 MG192 基因）及其重复染色体序列（称为 MgPars）。本研究的目的是研究 MgPa 操纵子和 MgPars 中三核苷酸串联重复（TTR）的位置、组织和可变性，并探讨 TTR 变异的可能机制和作用。通过分析 15 株地理分布不同的生殖道支原体临床分离株的完整 MgPa 操纵子和完整或部分 MgPar 序列，在 MG191 的四个区域、MG192 的一个区域以及除 MgPar3 之外的所有九个 MgPars 的两个或三个区域中鉴定出 TTR 序列。这些 TTR 不仅在重复拷贝数上，而且在菌株间或菌株内的重复单元序列上都存在变异性。TTR 变异的关键机制可能包括 MgPa 和 MgPars 之间的重组以及单链错配。TTR 变异可能代表一种最大限度地增加 MgPa 操纵子变异性的机制，这与涉及 MgPa 和 MgPars 之间片段重组的遗传变异互补，从而增强了生物体附着和定殖宿主细胞以及逃避宿主免疫系统的能力。
