Molecular Mechanisms of Organelle Formation in Bacteria

项目摘要 脂质结合的细胞器被吹捧为真核生物的一个定义特征，而这一特征在 建筑上原始的细菌细胞。然而，许多细菌使用脂类结合的细胞器来执行 以一种分隔的方式进行必要的、有时是有毒的生化反应。我的小组使用 趋磁细菌磁小体细胞器作为研究趋磁细菌致病机制的模型 细菌中细胞器的形成和功能。磁小体是细胞的脂双层内陷。 具有独特蛋白质含量的薄膜，其中纳米尺寸的铁基磁性晶体 制作。单个磁小体在肌动蛋白样细胞骨架的帮助下排列成链，因此 允许趋磁细菌使用地磁场作为低氧环境的简单指南。这个 磁小体的细胞生物学特性使其成为了解细胞器分子基础的理想材料 细菌的生物发生，或许还能揭示真核细胞器的进化起源。磁力 磁小体的物理性质使其成为生物医学发展的诱人目标 应用包括用作磁共振成像的造影剂、作为药物输送载体 并作为加热杀灭肿瘤细胞的介质。除了磁小体，我的团队最近 发现了一种新的积累铁的脂质结合细胞器，名为铁体。形成了铁素体 通过少量基因的作用，在不同的细菌中发现，包括常驻成员 肠道微生物群和机会性病原体。本提案中概述的研究计划将利用 我的团队中探索磁小体最关键领域的专业知识和现有知识 铁体生物学。首先，我们将专注于细胞生物学机制，它允许形成和 磁小体的亚细胞组织。我们将定义生物发生所需的最小组件 ，揭示蛋白质定位到磁小体的方式和动力学 并研究肌动蛋白样细胞骨架的生化和生物物理特性 磁小体的组织。第二，我们将研究铁的生物矿化机理。 磁小体。我们将揭示与成核有关的蛋白质的相互作用、活性和功能 和磁性粒子的生长，并将开发简化的体外系统来定义动力学和化学 生物矿化的要求。最后，我们将利用这个项目期将铁体开发成 用于细菌细胞器研究的交替且稳健的模型。我们将确定其机制。 铁体膜的生物发生、蛋白质分选和铁的运输，并平行地定义它们的生理 在相关微生物中发挥作用。这些方法的结合将揭示进化和 细菌细胞器的机械多样性及其在应用中的合理使用 设置。

Project Abstract Lipid-bounded organelles are touted as a defining feature of eukaryotes and one which is absent from the architecturally primitive cells of bacteria. However, numerous bacteria use lipid-bounded organelles to execute essential, and at times toxic, biochemical reactions in a compartmentalized fashion. My group uses the magnetosome organelles of magnetotactic bacteria as a model for understanding the mechanistic basis of organelle formation and function in bacteria. Magnetosomes are lipid-bilayer invaginations of the cell membrane with a unique protein content, within which nanometer-sized iron-based magnetic crystals are produced. Individual magnetosomes are arranged into a chain with the help of an actin-like cytoskeleton, thus allowing magnetotactic bacteria to use geomagnetic fields as a simple guide for low oxygen environments. The cell biological features of magnetosomes make them ideal for understanding the molecular basis of organelle biogenesis in bacteria and, perhaps, uncover the evolutionary origins of eukaryotic organelles. The magnetic and physical properties of magnetosomes make them attractive targets for the development of biomedical applications including their use as contrast agents for magnetic resonance imaging, as drug delivery vehicles and as a medium for hyperthermic killing of tumor cells. In addition to magnetosomes, my group has recently discovered a novel iron-accumulating lipid-bounded organelle named the ferrosome. Ferrosomes are formed through the action of a small number of genes and are found in diverse bacteria including resident members of the gut microbiome and opportunistic pathogens. The research program outlined in this proposal will leverage the expertise and existing knowledge within my group to explore the most critical areas of magnetosome and ferrosome biology. First, we will focus on the cell biological mechanisms that allow for formation and subcellular organization of magnetosomes. We will define the minimal components required for the biogenesis of the magnetosome membrane, uncover the modes and dynamics of protein localization to magnetosomes and study the biochemical and biophysical characteristics of the actin-like cytoskeleton required for organization of magnetosomes. Second, we will investigate the mechanisms of iron biomineralization within magnetosomes. We will uncover the interactions, activity and function of proteins implicated in the nucleation and growth of magnetic particles and will develop simplified in vitro systems to define the kinetics and chemical requirements for biomineralization. Finally, we will use this project period to develop ferrosomes into an alternate and robust model for the study of bacterial organelles. We will determine the mechanisms of ferrosome membrane biogenesis, protein sorting and iron transport and in parallel define their physiological function in relevant microorganisms. The combination of these approaches will shed light on the evolution and mechanistic diversity of bacterial organelles while providing a more rational basis for their use in applied settings.