Betts-Hampikian Helen Jennifer, Fields Kenneth A
Department of Microbiology and Immunology, University of Miami Miller School of Medicine Miami, FL, USA.
Front Microbiol. 2010 Oct 19;1:114. doi: 10.3389/fmicb.2010.00114. eCollection 2010.
Present-day members of the Chlamydiaceae contain parasitic bacteria that have been co-evolving with their eukaryotic hosts over hundreds of millions of years. Likewise, a type III secretion system encoded within all genomes has been refined to complement the unique obligate intracellular niche colonized so successfully by Chlamydia spp. All this adaptation has occurred in the apparent absence of the horizontal gene transfer responsible for creating the wide range of diversity in other Gram-negative, type III-expressing bacteria. The result is a system that is, in many ways, uniquely chlamydial. A critical mass of information has been amassed that sheds significant light on how the chlamydial secretion system functions and contributes to an obligate intracellular lifestyle. Although the overall mechanism is certainly similar to homologous systems, an image has emerged where the chlamydial secretion system is essential for both survival and virulence. Numerous apparent differences, some subtle and some profound, differentiate chlamydial type III secretion from others. Herein, we provide a comprehensive review of the current state of knowledge regarding the Chlamydia type III secretion mechanism. We focus on the aspects that are distinctly chlamydial and comment on how this important system influences chlamydial pathogenesis. Gaining a grasp on this fascinating system has been challenging in the absence of a tractable genetic system. However, the surface of this tough nut has been scored and the future promises to be fruitful and revealing.
衣原体科目前的成员包含寄生细菌，这些细菌在数亿年的时间里一直与其真核宿主共同进化。同样，所有基因组中编码的III型分泌系统也得到了优化，以适应衣原体属成功定殖的独特专性细胞内生态位。所有这些适应性变化显然是在缺乏水平基因转移的情况下发生的，而水平基因转移正是导致其他革兰氏阴性、表达III型的细菌产生广泛多样性的原因。其结果是形成了一个在许多方面都具有独特衣原体特征的系统。目前已经积累了大量信息，这些信息为衣原体分泌系统的功能以及它如何促成专性细胞内生活方式提供了重要线索。尽管总体机制肯定与同源系统相似，但衣原体分泌系统对于生存和毒力都至关重要的形象已经浮现出来。衣原体III型分泌与其他分泌存在许多明显差异，有些细微，有些则很显著。在此，我们全面综述了关于衣原体III型分泌机制的当前知识状态。我们重点关注衣原体特有的方面，并评论这个重要系统如何影响衣原体发病机制。在缺乏易于处理的遗传系统的情况下，要深入了解这个迷人的系统一直具有挑战性。然而，这个难题的表面已经有了突破口，未来有望取得丰硕成果并揭示更多奥秘。
