RpoS controls the Vibrio cholerae mucosal escape response.
RpoS controls the Vibrio cholerae mucosal escape response.
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DOI：
10.1371/journal.ppat.0020109
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发表时间：
2006-10
期刊：
影响因子：
6.7
通讯作者：
Schoolnik, Gary K
中科院分区：
文献类型：
--
作者：
Nielsen, Alex Toftgaard;Dolganov, Nadia A;Otto, Glen;Miller, Michael C;Wu, Cheng Yen;Schoolnik, Gary K
霍乱弧菌通过在小肠上皮定殖期间分泌毒素而引起严重的小肠疾病。虽然感染过程的初始阶段已经得到了深入的研究，但最后阶段却很少受到关注。霍乱弧菌O1感染的兔回肠袢的共聚焦显微镜捕获了感染过程中的一个独特阶段：接种后12小时，细菌从上皮表面分离并进入充满液体的管腔。指定的“粘膜逃逸反应”，这种现象需要RpoS，固定相交替西格玛因子。定量体内定位测定证实了rpoS表型，并表明它也需要HapR。从回肠袢液和粘液中分离的细菌的表达谱显示许多趋化性和运动性基因的显著Rpos依赖性上调与细菌从上皮表面的迁移一致。在静止期培养物中，RpoS也需要上调趋化性和运动性基因，用于产生鞭毛，以及用于细菌在低营养群板中的移动。hapR突变体产生接近正常数量的鞭毛细胞，但明显不如野生型亲本能动。在毒性诱导条件下的体外生长过程中，rpoS突变体产生的霍乱毒素比野生型亲本多10至100倍。尽管rpoS突变体仅引起回肠环中编码霍乱毒素的基因的少量过度表达，但与野生型相比，其导致液体积聚增加30%。总之，这些结果表明，粘膜逃逸反应是由Rpos依赖的遗传程序，激活趋化性和运动功能。此外，这可能与毒性基因表达减少相一致，从而为生物体生命周期的下一阶段做好准备。霍乱弧菌是一种致病微生物，主要在第三世界国家引起严重的肠道疾病。虽然这种微生物的致病性已经被深入研究了世纪，但大多数研究都集中在感染的初始阶段，特别是肠道定植和毒力基因表达。然而，感染过程的最后阶段很少受到关注。在目前的手稿中，作者使用兔回肠袢霍乱模型来显示这种生物体在感染后期如何从上皮表面脱离并迁移到腔液中，作者将这一过程称为“粘膜逃逸反应”。这项研究确定，第一次，如何替代饥饿西格玛因子RpoS调节这一过程。这个遗传程序的特点包括参与运动和趋化功能的基因的戏剧性诱导。该研究进一步确定RpoS是毒力基因表达的重要调节因子，并表明粘膜逃逸反应可能与毒力基因表达的减少相一致。这项工作对于了解这种重要的人类病原体生命周期中关键且未被充分认识的步骤至关重要：它从肠道中退出，以及这如何使其准备好传播到环境水库或新的人类宿主中。
Vibrio cholerae causes a severe diarrhoeal disease by secreting a toxin during colonization of the epithelium in the small intestine. Whereas the initial steps of the infectious process have been intensively studied, the last phases have received little attention. Confocal microscopy of V. cholerae O1-infected rabbit ileal loops captured a distinctive stage in the infectious process: 12 h post-inoculation, bacteria detach from the epithelial surface and move into the fluid-filled lumen. Designated the “mucosal escape response,” this phenomenon requires RpoS, the stationary phase alternative sigma factor. Quantitative in vivo localization assays corroborated the rpoS phenotype and showed that it also requires HapR. Expression profiling of bacteria isolated from ileal loop fluid and mucus demonstrated a significant RpoS-dependent upregulation of many chemotaxis and motility genes coincident with the emigration of bacteria from the epithelial surface. In stationary phase cultures, RpoS was also required for upregulation of chemotaxis and motility genes, for production of flagella, and for movement of bacteria across low nutrient swarm plates. The hapR mutant produced near-normal numbers of flagellated cells, but was significantly less motile than the wild-type parent. During in vitro growth under virulence-inducing conditions, the rpoS mutant produced 10- to 100-fold more cholera toxin than the wild-type parent. Although the rpoS mutant caused only a small over-expression of the genes encoding cholera toxin in the ileal loop, it resulted in a 30% increase in fluid accumulation compared to the wild-type. Together, these results show that the mucosal escape response is orchestrated by an RpoS-dependent genetic program that activates chemotaxis and motility functions. This may furthermore coincide with reduced virulence gene expression, thus preparing the organism for the next stage in its life cycle. Vibrio cholerae, a pathogenic microbe, causes a severe diarrhoeal disease mainly in Third World countries. Although the pathogenicity of this organism has been intensively studied for more than a century, most research has focused on the initial stages of the infection, especially colonization of the intestine and virulence gene expression. However, the last stages of the infectious process have received very little attention. In the present manuscript, the authors use the rabbit ileal loop model of cholera to show how this organism, late in the infection, detaches from the epithelial surface and migrates into the luminal fluid, a process the authors termed the “mucosal escape response.” This study identifies, for the first time, how the alternative starvation sigma factor RpoS regulates this process. Features of this genetic program include the dramatic induction of genes involved in motility and chemotaxis functions. This study furthermore identifies RpoS as an important regulator of virulence gene expression and shows that the mucosal escape response may coincide with diminished virulence gene expression. This work is essential for understanding a key and under-appreciated step in the life cycle of this important human pathogen: its exit from the intestine and how this serves to prepare it for transmission into environmental reservoirs or to new human hosts.