Understanding the role of sensory adaptation in bacterial mechanochemical signaling pathways

项目摘要/摘要 铜绿假单胞菌(PA)是一种多功能的机会致病菌，是导致医院感染的主要原因。 免疫功能低下患者和囊性纤维化患者的获得性感染。PA抗生素耐药性 继续呈爆炸式增长，这使得开发新的治疗方法成为迫切需要。这是革兰氏阴性 细菌编码了大量的所谓的双组分信号转导系统， 细菌感知和响应外部环境变化的主要信号机制， 包括4个化学传感类系统。化学感觉系统的一个独特特征是它们能够 感觉适应，化学感觉系统返回到刺激前的短期记忆过程 尽管持续暴露在输入信号中，但仍处于最高电平。在E.ColiChe系统中，适应涉及可逆的 MCP上一个或多个谷氨基残基的甲基化和去甲基化。这是通过 组成活性Cher甲基转移酶的酶活性和CHEB的调节活性 甲酯酶通过一个本质上是延迟的负反馈电路。重要的是，雪儿和切伯 同源基因在一系列不同于大肠杆菌范例的化学传感类系统中是保守的 在他们的输入和输出中。因此，关于机械性后果仍有许多需要了解。 以及在趋化作用之外的适应的生理作用，例如在生物膜形成期间。 我们的实验室和其他实验室已经描述了CHP化学传感系统，这是编码的4个化学传感系统之一 在宾夕法尼亚州。我们最近发现，chp的化学传感系统起着机械力化学物质的作用。 通过收缩IV型极化毛发(TFP)来感觉表面接触的信号系统(MCS) 粘附素。随后通过CHP MCS的磷继电器导致两个输出：(I)独特形式的调节 表面运动，依赖于IV型纤毛(TFP)的抽动运动，以及(Ii)涉及&gt；200基因的转录 在急性毒力、群体感应和生物膜形成的启动中。后续生物膜的形成需要 循环-二-GMP激活的程序。 尽管CHP系统编码一个假定的甲基转移酶和甲基酯酶，但人们对此知之甚少。 关于感官适应如何在调节其输出方面发挥作用。这是耐人寻味的，因为生防护系统 对表面接触作出反应，而不对化学梯度作出反应。我们假设CHP MCS系统利用 感觉适应，在表面接触时微调第二信使水平，以促进过渡 从浮游生长到生物膜形成。在这个提案中，我们将检验以下假设：(1)Pilk和 ChpB是具有甲基化和去甲基化功能的极化定位蛋白；(2)Pilk/ChpB/PilJ- CHP MCS中介导的感觉适应调节表面的幅度和动力学 激活的毒力程序和/或抽动运动的动力学；以及(3)CHP MCS感觉 从浮游生长向生物膜形成的转变需要适应。

PROJECT SUMMARY/ABSTRACT Pseudomonas aeruginosa (PA) is a versatile opportunistic pathogen that is a leading cause of hospital- acquired infections in immunocompromised patients and in patients with Cystic Fibrosis. PA antibiotic resistance continues to explode, making development of new therapeutic approaches a critical need. This gram-negative bacterium encodes an unusually large number of so called two-component signal transduction systems, the major signaling machinery by which bacteria sense and respond to changes in their external environment, including 4 chemosensory-like systems. A unique feature of chemosensory systems is their ability to undergo sensory adaption, a short-term memory process by which the chemosensory system returns to its pre-stimulus level despite ongoing exposure to the input signal. In the E. coli Che system, adaptation involves the reversible methylation and demethylation of one or more glutamyl residues on the MCP. This is accomplished through the enzymatic activity of the constitutively active CheR methyltransferase and the regulated activity of the CheB methylesterase through what is essentially a delayed negative feedback circuit. Importantly, the CheR and CheB homologs are conserved in a diverse array of chemosensory-like systems that differ from the E. coli paradigm in their inputs and outputs. Therefore, much remains to be learned about the mechanistic consequences and physiologic roles of adaptation outside of chemotaxis, for example during biofilm formation. Our lab and others have described the Chp chemosensory system, one of 4 chemosensory systems encoded in PA. We have recently discovered that the Chp chemosensory system functions as a mechanochemical signaling (MCS) system that senses surface contact through retraction of the polarly localized type IV pilus (TFP) adhesin. Subsequent phosphorelay through the Chp MCS leads to two outputs: (i) regulation of a unique form of surface locomotion, type IV pili (TFP)-dependent twitching motility, and (ii) transcription of >200 genes involved in acute virulence, quorum sensing, and initiation of biofilm formation. Subsequent biofilm formation requires a cyclic-di-GMP-activated program. Even though the Chp system encodes a presumptive methyltransferase and methylesterase, little is known about how sensory adaptation might play a role in regulating its outputs. This is intriguing as the Chp system responds to surface contact and not to chemical gradients. We hypothesize that the Chp MCS system utilizes sensory adaption to finely tune second messenger levels upon surface contact to facilitate the transition from planktonic growth to biofilm formation. In this proposal we will test the hypotheses that (1) PilK and ChpB are polarly localized proteins that function to methylate and demethylate PilJ; (2) PilK/ChpB/PilJ- mediated sensory adaptation in the Chp MCS regulates the amplitude and kinetics of the surface- activated virulence program and/or the dynamics of twitching motility; and (3) The Chp MCS sensory adaptation is required for the transition from planktonic growth to biofilm formation.