PLoS Patho：揭示泳动现象或更易于鼠伤寒沙门菌进行感染靶点的选择

近日，国际著名杂志<em>PLoS Pathogens</em>在线刊登了瑞士苏黎世联邦理工学院研究者的最新研究成果“Near Surface Swimming of Salmonella Typhimurium Explains Target-Site Selection and Cooperative Invasion”，文章中，研究者揭示了泳动现象或更易于鼠伤寒沙门菌进行感染靶点的选择。

鼠伤寒沙门菌（S. Typhimurium）是一种重要的人畜共患病原菌，其感染发病率居沙门菌感染的首位，常见于婴幼儿发病，而且可引发医院感染和暴发性食物中毒，病死率非常之高。以特许进入位点为靶点是细菌感染的重要一步，目前这种目标机制并不清楚。

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因此，文章中，研究者分析了S. Typhimurium的靶位选择性，这种肠病源细菌拥有细菌细胞表面配基和三型分泌系统，对于结合宿主非常重要，往往可以引发疾病。

使用建立好的组织模型培养系统，研究者发现了鞭毛驱使的运动可以促使细菌发生泳动（swimming motility），这就使得细菌更加容易扫描到宿主表面，从而进行吸附，进一步感染。这种表面泳动现象是细菌独特的拓扑学特性，如圆细胞和细胞褶皱。这也就解释了S. Typhimurium如何识别特殊的把微点来吸附至宿主细胞膜从而引发感染。

更有意思的是，细菌这种泳动是通过特殊的物理原理来引发的运动，因此，研究者的研究发现为能动致病菌的感染以及其治疗提供了一定的思路。 
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<a title="" href="http://dx.doi.org/doi:10.1371/journal.ppat.1002810" target="_blank">doi:10.1371/journal.ppat.1002810</a>
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<br/><strong>Near Surface Swimming of Salmonella Typhimurium Explains Target-Site Selection and Cooperative Invasion</strong><br/>


Benjamin Misselwitz1#, Naomi Barrett1#, Saskia Kreibich1, Pascale Vonaesch1, Daniel Andritschke1, Samuel Rout1, Kerstin Weidner1, Milos Sormaz2, Pascal Songhet1, Peter Horvath3, Mamta Chabria4, Viola Vogel4, Doris M. Spori2, Patrick Jenny5, Wolf-Dietrich Hardt1*

Targeting of permissive entry sites is crucial for bacterial infection. The targeting mechanisms are incompletely understood. We have analyzed target-site selection by S. Typhimurium. This enteropathogenic bacterium employs adhesins (e.g. fim) and the type III secretion system 1 (TTSS-1) for host cell binding, the triggering of ruffles and invasion. Typically, S. Typhimurium invasion is focused on a subset of cells and multiple bacteria invade via the same ruffle. It has remained unclear how this is achieved. We have studied target-site selection in tissue culture by time lapse microscopy, movement pattern analysis and modeling. Flagellar motility (but not chemotaxis) was required for reaching the host cell surface in vitro. Subsequently, physical forces trapped the pathogen for ~1.5–3 s in “near surface swimming”. This increased the local pathogen density and facilitated “scanning” of the host surface topology. We observed transient TTSS-1 and fim-independent “stopping” and irreversible TTSS-1-mediated docking, in particular at sites of prominent topology, i.e. the base of rounded-up cells and membrane ruffles. Our data indicate that target site selection and the cooperative infection of membrane ruffles are attributable to near surface swimming. This mechanism might be of general importance for understanding infection by flagellated bacteria.

<br/>来源：生物谷

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