Mechanisms for sensing and responding to interbacterial antagonism

项目摘要 越来越明显的是，种间拮抗作用是细菌界生命所固有的。和 然而，尽管我们了解细菌在与它们的兄弟发生冲突时所使用的抗菌机制， 最近呈指数级增长，我们对细菌感知和反应的方式的了解 对抗性威胁仍然有限。在这个提议中，我们测试了细菌对存在的反应的假设， 通过激活多方面的防御程序来对抗细菌竞争者。这 我们发现铜绿假单胞菌激活了一个广泛的转录后 调节程序响应细菌间的拮抗作用。我们称之为帕拉的途径 （铜绿假单胞菌对拮抗作用的反应），当铜绿假单胞菌细胞亚群 作为对抗性攻击的结果而屈服于溶解。检测细胞中尚未鉴定的分子 裂解物导致小RNA介导的Gac/Rsm全局转录后调节蛋白的激活。 程序.这种反应的激活对于铜绿假单胞菌在攻击期间的存活至关重要，因为突变体不能 在与拮抗生物体的竞争过程中，该反应遭受严重的适合度缺陷。最后我们 证明防御反应需要多种同时起作用的机制，包括 未知功能的路径。在本提案的目标1中，我们将描述一种这样的途径， 名称ARC 1（拮抗反应复合物1）。我们的初步数据表明ARC 1是一个大的膜- 提供铜绿假单胞菌对抗毒素介导的拮抗作用的相关蛋白复合物 通过竞争物种的VI型分泌系统递送。我们对ARC 1的研究将阐明 它提供保护，并提供对其防御功能的机械洞察力。在 目标2，我们将追求互补的遗传和生物化学方法，旨在表征信号 最后，在目标3中，我们超越了铜绿假单胞菌。 铜绿假单胞菌，并询问帕拉-Gac/Rsm途径- 在其他假单胞菌属物种中通常起防御细菌间拮抗作用的作用。我们也 检查Gac/Rsm调节子的变异性反映了对特定细菌的适应性的假设 不同物种面临的威胁通过这项工作，我们将回答长期存在的问题， 领域，包括定义一个重要的全球监管计划的进化相关功能， 提供长的难以捉摸的信号分子的分子表征。此外，通过 ARC 1的特性，我们的工作将定义参与保守的膜的机制基础 复合体在细菌间防御中的未知功能。总的来说，拟议的工作将扩大我们的 了解细菌间的拮抗作用如何塑造细菌进化的过程。

Project Summary It is increasingly evident that interspecies antagonism is intrinsic to life in the bacterial kingdom. And yet, while our understanding of the antibacterial mechanisms bacteria employ in conflicts with their brethren has recently grown exponentially, our knowledge of the means by which bacteria sense and respond to antagonistic threats remains limited. In this proposal, we test the hypothesis that bacteria react to the presence of an antagonistic bacterial competitor through the activation of a multifaceted defensive program. This hypothesis grew from our discovery that Pseudomonas aeruginosa activates an extensive posttranscriptional regulatory program in response to interbacterial antagonism. The pathway, which we term PARA (Pseudomonas aeruginosa response to antagonism), is triggered when a subpopulation of P. aeruginosa cells succumb to lysis as a result of an antagonistic attack. Detection of as yet unidentified molecule(s) in cellular lysate leads to the activation of the small RNA-mediated Gac/Rsm global posttranscriptional regulatory program. Activation of this response is crucial for P. aeruginosa survival during attack, as a mutant unable to mount the response suffers a severe fitness defect during competition with antagonistic organisms. Finally, we demonstrate that the defensive response requires multiple, simultaneously acting mechanisms, including pathways of unknown function. In Aim 1 of this proposal, we will characterize one such pathway, which we name ARC1 (antagonism response complex 1). Our preliminary data indicate that ARC1 is a large membrane- associated protein complex that provides P. aeruginosa protection against antagonism mediated by toxins delivered by the type VI secretion system of a competitor species. Our studies of ARC1 will elucidate the range of threats towards which it provides protection and provide mechanistic insight into its defensive functions. In Aim 2, we will pursue complementary genetic and biochemical approaches directed at characterizing the signal present in P. aeruginosa cellular lysate responsible for triggering PARA. Finally, in Aim 3, we move beyond P. aeruginosa and ask to what extent the regulatory components behind PARA – the Gac/Rsm pathway – function generally to defend against interbacterial antagonism in other Pseudomonas species. We also examine the hypothesis that variability in the Gac/Rsm regulon reflects adaptation to the specific bacterial threats encountered by different species. Through this work, we stand to answer longstanding questions in the field, including defining the evolutionarily relevant function of an important global regulatory program and providing a molecular characterization of a long elusive signaling molecule. Additionally, through the characterization of ARC1, our work will define the mechanistic basis for participation of a conserved membrane complex of unknown function in interbacterial defense. Overall, the proposed work stands to broaden our understanding of the ways in which interbacterial antagonism shapes the course of bacterial evolution.