Host-associated biofilm formation and dispersal mechanisms

摘要 细菌可以形成多细胞群落，其中单个细胞受到保护免受环境的侵害 例如抗生素，由于被包裹在由多糖和其它多糖组成的保护性基质中， 大分子和[2]生理上不同于自由生活的细胞。生物膜形成增强 细菌在表面，包括宿主组织和非生物表面如医用植入物， 并通过传播过程在远端位置播种随后的感染。由于这些 由于生物膜的特性，生物膜中的细菌是大多数医院获得性感染的原因，因此， 理解生物膜如何形成和从这种生物膜中分散是至关重要的。尽管有许多动物模型 虽然已经开发了生物膜形成的方法，但是很少（如果有的话）允许目视检查生物膜形成， 扩散事件以及随后的殖民结果的定量分析。一个这样的鲁棒模型， 然而，可以在费氏弧菌-鱿鱼（Euprymna squidopes）共生体中发现。为了殖民，首先是费氏弧菌 在共生器官的表面形成生物膜，然后从其分散进入并最终定殖于位点 在这个器官的深处。我们的工作表明，在实验室培养中，生物膜形成所需的基因是 同样需要宿主相关（HA）生物膜和定植，而基因变化，增强 实验室中的生物膜形成也显著增强HA生物膜和定殖。这种强相关性提供了 我们一个特殊的机会，发展和测试有关HA生物膜，分散机制的假设， 随后的殖民。我们的工作揭示了HA生物膜和定殖依赖于syp，一个18- 参与SYP多糖产生的基因位点，以及多个传感器激酶和反应调节因子 控制syp转录和转录后事件。我们最近发现钙（Ca 2+）和 一氧化氮（NO）分别作为生物膜形成的强诱导剂和抑制剂。Ca 2+是一种生理上 相关的信号，似乎影响了许多进程，但它是如何做到这一点是未知的。不，这是 由鱿鱼产生并已知会影响HA生物膜，可能会影响一种传感器激酶， syp转录，我们建议评估潜在的机制。我们还准备确定其他 促进/抑制HA生物膜的生理信号。我们最近发现了 在实验室培养中可以观察到传播，并观察到V. fischeri经历多轮 在完全生长的培养物中形成和传播的过程，这一结果表明转录后控制。 机制等我们已经开始研究这一过程，确定了一组基因参与控制 分散我们建议对这些传播基因和影响传播的因素进行机械的理解。 控制扩散事件以及寻找我们预测存在的其他事件。我们预计这项工作将 深入了解细菌对环境的反应机制，以及细菌进出环境的机制。 动物宿主体内的多细胞群落。

Abstract Bacteria can form multi-cellular communities in which individual cells are protected from environmental insults such as antibiotics by virtue of being [1] encased in a protective matrix comprised of polysaccharides and other macromolecules and [2] physiologically distinct from free-living, planktonic cells. Biofilm formation enhances the ability of bacteria to colonize surfaces, including host tissues and abiotic surfaces such as medical implants, and seeds subsequent infections at distal locations through dispersal processes. As a result of these characteristics, bacteria in biofilms are responsible for the majority of hospital-acquired infections and thus understanding how biofilms form and disperse from such biofilms is critical. Although numerous animal models of biofilm formation have been developed, few, if any, permit visual examination of biofilm formation and dispersal events as well as a quantitative analysis of subsequent colonization outcomes. One such robust model, however, can be found in the Vibrio fischeri-squid (Euprymna scolopes) symbiosis. To colonize, V. fischeri first forms a biofilm on the surface of the symbiotic organ, then disperses from it to enter and ultimately colonize sites deep within this organ. Our work has shown that genes required for biofilm formation in laboratory culture are similarly required for host-associated (HA) biofilms and colonization, while genetic changes that enhance biofilm formation in the lab also strikingly enhance HA biofilms and colonization. This strong correlation affords us an exceptional opportunity to develop and test hypotheses about the mechanisms of HA-biofilms, dispersal and subsequent colonization. Our work has revealed that HA biofilms and colonization depend on syp, an 18- gene locus involved in production of SYP polysaccharide, and on multiple sensor kinases and response regulators that control syp transcription and post-transcriptional events. We have recently identified calcium (Ca2+) and nitric oxide (NO) as a strong inducer and inhibitor, respectively, of biofilm formation. Ca2+ is a physiologically relevant signal that appears to affect numerous processes, but how it does so is as-yet unknown. NO, which is produced by the squid and known to influence HA-biofilms, likely impacts one of the sensor kinases required for syp transcription, and we propose to evaluate the underlying mechanisms. We are also poised to identify other physiological signals that promote/inhibit HA biofilms. We have recently uncovered conditions in which dispersal can be visualized in laboratory culture, and have observed that V. fischeri undergoes multiple rounds of formation and dispersal in fully-grown cultures, a result that suggests control by post-transcriptional mechanisms. We have begun to investigate that process by identifying a set of genes involved in controlling dispersal. We propose to develop a mechanistic understanding of these dispersal genes and the factors that control dispersal events as well as to search for others that we predict to exist. We anticipate that this work will provide insights into the mechanisms by which bacteria respond to their environment and transition in and out of multi-cellular communities within an animal host.