Function and maintenance of molecules at the surface of Acinetobacter baumannii

摘要 细菌进化出不同的细胞膜成分，这些成分为它们提供了天然的 环境或作为人类病原体。两种主要类型的皮肤病细菌，含有两种细胞膜 脂膜，已被发现因其外膜表面的组成而不同 (OM)。革兰氏阴性细菌(如大肠杆菌)含有一层脂多糖(LPS)， 在OM处产生严格的渗透屏障，使它们对许多抗生素具有抗药性。此外, 内毒素的生物发生在大多数革兰氏阴性细菌中是必不可少的，尽管原因仍然不清楚。 其他丝虫(如许多螺旋体)的表面有甘油磷脂(GPL)和脂蛋白 奥姆。表面脂蛋白在发病机制、营养获取和信号转导中起着许多关键作用。然而， 对于大多数发现脂蛋白的细菌来说，脂蛋白是如何到达OM表面的还是个未知数。 高度优先的革兰氏阴性病原体鲍曼不动杆菌能够在OM中存活 表面含有内毒素或甘油三酯和脂蛋白。鲍曼不动杆菌自然产生一种内毒素- 含有OM的。然而，该细菌能够在完全灭活内毒素生物合成的情况下存活。损失 细胞表面的脂蛋白伴随着表面暴露的脂蛋白的上调。首要目标是 这一应用的目的是研究细胞表面分子的功能和组装，内毒素和 脂蛋白，使用含有内毒素和缺乏内毒素的鲍曼不动杆菌。在目标1中，我们将采取两个定向 方法，以研究表面脂蛋白在内毒素缺乏期间的作用，以及一种无偏见的方法，以 确定对内毒素缺乏的鲍曼不动杆菌的额外遗传要求。在目标2中，我们将描述如何 在鲍曼不动杆菌中，脂蛋白到达OM表面。我们将针对与脂蛋白运输有关的基因 在其他细菌中，并进行无偏筛选以识别与表面定位有关的基因。这个 鲍曼曲霉在两种不同的OM成分中生长的非凡能力，为 探索每种方法为细菌细胞提供的优势。这个应用程序建立在强大的科学前提之上 解决我们对鲍曼氏杆菌病原体了解中的主要差距，将具有广泛的意义 关于革兰氏阴性菌和其他皮肤病细菌的细胞膜生物发生和可能的治疗。 申请表将由M.斯蒂芬·特伦特博士(赞助商)实验室的首席研究员在 佐治亚大学。这两个机构都致力于为学员提供研究(例如 基因组学、显微镜等)和职业发展资源(例如，技能培训、教学、 辅导等)。研究金的完成将提供新技术(如脂类组学)、新领域的培训 研究(例如基因组学)，以及为在学术界从事独立研究工作做准备的关键技能。

Abstract Bacteria have evolved different cell envelope compositions that provide them specific advantages in their natural environments or as human pathogens. Two major types of didermic bacteria, containing cell envelopes with two lipid membranes, have been discovered that differ by the composition of the surface of their outer membranes (OM). Gram-negative bacteria (e.g. Escherichia coli) contain a surface layer of lipopolysaccharides (LPS) that produces a stringent permeability barrier at the OM and make them resistant to many antibiotics. In addition, LPS biogenesis is essential in most Gram-negative bacteria, although the reason why has remained elusive. Other diderms (e.g. many spirochetes) have glycerophospholipids (GPLs) and lipoproteins at the surface of the OM. Surface lipoproteins have many critical roles in pathogenesis, nutrient acquisition, and signaling. However, how lipoproteins reach the surface of the OM has remained unknown for most bacteria in which they are found. The high-priority Gram-negative pathogen, Acinetobacter baumannii, is remarkably able to survive with an OM containing either LPS or GPLs and lipoproteins at the surface. A. baumannii naturally produces an LPS- containing OM. However, this bacterium is able to survive with complete inactivation of LPS biogenesis. Loss of LPS at the cell surface is accompanied by up-regulation of surface-exposed lipoproteins. The primary objective of this application is to investigate the function and assembly of molecules on the surface of the cell, LPS and lipoproteins, using LPS-containing and LPS-deficient A. baumannii. In Aim 1, we will take both a directed approach, to investigate the role of surface lipoproteins during LPS-deficiency, and a non-biased approach, to identify additional genetic requirements for LPS-deficient A. baumannii. In Aim 2, we will characterize how lipoproteins reach the surface of the OM in A. baumannii. We will target genes implicated in lipoprotein transport in other bacteria, and perform an unbiased screen to identify genes involved in surface localization. The remarkable ability of A. baumannii to grow with two different OM compositions, provides a unique opportunity to explore the advantages each provides to bacterial cells. This application is built on a strong scientific premise addressing major gaps in our understanding of the pathogen, A. baumannii, that will have broad implications towards cell envelope biogenesis and possible treatment of both Gram-negative and other didermic bacteria. The application will be completed by the principal investigator in the lab of Dr. M. Stephen Trent (sponsor) at the University of Georgia. Both of which are committed to providing trainees with research (e.g. core facilities in genomics, microscopy, etc.) and career development resources (e.g. training in grantsmanship, teaching, mentoring, etc.). Completion of the fellowship will provide training in new techniques (e.g. lipidomics), new fields of research (e.g. genomics), and critical skills to prepare for a career as an independent researcher in academia.