Iverson-Cabral Stefanie L, Astete Sabina G, Cohen Craig R, Totten Patricia A
Department of Pathobiology, University of Washington, Seattle, WA 98104, USA.
Mol Microbiol. 2007 Oct;66(1):55-73. doi: 10.1111/j.1365-2958.2007.05898.x.
Mycoplasma genitalium is associated with sexually transmitted infections in men and women that, if untreated, can persist, suggesting that mechanism(s) exist to facilitate immune evasion. Approximately 4% of the limited M. genitalium genome contains repeat sequences termed MgPar regions that have homology to mgpB and mgpC, which encode antigenic proteins associated with attachment. We have previously shown that mgpB sequences vary within a single strain of M. genitalium in a pattern consistent with recombination between mgpB and MgPar sequences (Iverson-Cabral et al.). In the current study, we show that mgpC heterogeneity similarly occurs within the type strain, G-37(T), cultured in vitro and among cervical specimens collected from a persistently infected woman. In all cases, alternative mgpC sequences are indicative of recombination with MgPar regions. Additionally, the isolation of single-colony M. genitalium clonal variants containing alternative mgpB or mgpC sequences allowed us to demonstrate that mgpB and mgpC heterogeneity is associated with corresponding changes within donor MgPar regions, consistent with reciprocal recombination. Better-defined systems of antigenic variation are typically mediated by unidirectional gene conversion, so the generation of genetic diversity observed in M. genitalium by the mutual exchange of sequences makes this organism unique among bacterial pathogens.
生殖支原体与男性和女性的性传播感染有关，如果不进行治疗，感染可能会持续存在，这表明存在促进免疫逃逸的机制。在有限的生殖支原体基因组中，约4%包含被称为MgPar区域的重复序列，这些序列与mgpB和mgpC具有同源性，mgpB和mgpC编码与黏附相关的抗原蛋白。我们之前已经表明，在单个生殖支原体菌株中，mgpB序列以一种与mgpB和MgPar序列之间的重组相一致的模式发生变化（艾弗森 - 卡布拉尔等人）。在当前的研究中，我们表明，mgpC的异质性同样发生在体外培养的模式菌株G-37(T)以及从一名持续感染的女性收集的宫颈标本中。在所有情况下，替代的mgpC序列都表明与MgPar区域发生了重组。此外，分离出含有替代mgpB或mgpC序列的单菌落生殖支原体克隆变体，使我们能够证明mgpB和mgpC的异质性与供体MgPar区域内的相应变化相关，这与相互重组一致。通常，定义更明确的抗原变异系统是由单向基因转换介导的，因此在生殖支原体中通过序列的相互交换观察到的遗传多样性的产生，使得这种生物体在细菌病原体中独一无二。
