Extending the new respiratory paradigm in Bacteroides

项目总结/摘要 尽管在过去的15年里产生了大量关于人类的数据， 虽然我们对肠道微生物的能量产生过程知之甚少，但大多数丰富的肠道微生物 这个生态系统的成员，包括拟杆菌。我们在这一基本知识上的差距阻碍了我们 了解微生物成员之间的相互作用，肠道环境中的某些条件如何影响 微生物组成的变化，以及我们如何适当地改变生态系统的组成， 改善人类健康。拟杆菌属是人类最丰富和最稳定的细菌属之一 肠道微生物群与菌株殖民他们的主机几十年。在该项目的第一个供资周期， 我们证明了拟杆菌有一个复杂的呼吸链，在呼吸过程中提供大量的能量。 厌氧和纳米需氧（0.1- 0.15%O2）生长。我们的研究揭示了许多步骤的复杂性， 呼吸途径和拟杆菌属物种之间意想不到的差异，将在 这一更新申请。呼吸的这些新方面将在三个具体目标中得到解决。在Aim中 1，我们将研究重要的NUO复合物，该复合物将电子转移到甲基萘醌， 质子梯度的产生。拟杆菌NUO复合体与大多数研究的细菌不同。在 为此，我们将使用遗传学和生物化学分析来最终确定NUO的电子供体， 确定NUO和Na+/H+反向转运蛋白在维持必要质子梯度中的重要性，以及 确定NUO和Na+/H+反向转运蛋白对哺乳动物肠道中细菌适应性的贡献。在Aim中 2、研究呼吸系统中重要的呼吸成分甲基萘醌（menaquinone，MK）的获得和重构。 大多数拟杆菌具有MK从头合成所必需的所有基因;然而，某些拟杆菌具有MK从头合成所必需的所有基因。 拟杆菌属物种缺乏主要的men基因，并且必须获得和改造膳食和/或微生物营养素。 源我们将探索MK合成的未知特征，包括类异戊二烯链是如何裂解的 和改造，如何Bacteroides物种没有男性操纵子获得MK前体，以及饮食 和/或这些前体的微生物群来源。在目标3中，我们将研究NrfHA复合物，即以下基因： 它们是在纳米需氧生长过程中上调最多的。我们预测NrfHA是一个额外的终端 在纳米需氧条件下起作用并向亚硝酸盐和硝酸盐提供电子的电子供体 氧化物（NO），解毒这些分子。我们将研究nrfHA操纵子揭示的调控 在纳米需氧生长过程中上调基因的转录因子，研究其捐赠电子的能力 亚硝酸盐和NO，并确定这种复合物是否允许拟杆菌减少宿主炎症， 更好地在发炎的肠道中生存这项提议的实验将揭示基本的 拟杆菌的生理学可以转化为人类健康的好处。

Project Summary/Abstract Despite the tremendous amount of data that has been generated over the last 15 years regarding the human intestinal microbiota, we still know relatively little about energy generation processes of most of the abundant members of this ecosystem, including the Bacteroides. Our gap in this fundamental knowledge hinders our understanding of interactions between microbial members, how certain conditions in the gut environment affect microbial compositional changes, and how we may appropriately alter the composition of the ecosystem to improve human health. Bacteroides is one of the most abundant and stable bacterial genera of the human intestinal microbiota with strains colonizing their hosts for decades. During the first funding cycle of this project, we demonstrated that Bacteroides have a complex respiratory chain that provides substantial energy during both anaerobic and nanaerobic (0.1-0.15% O2) growth. Our studies revealed complexity at many steps in the respiration pathway and unexpected differences between Bacteroides species that will be pursued in this renewal application. These new aspects of respiration will be addressed in three specific aims. In Aim 1, we will study the important NUO complex that couples the transfer of electrons to menaquinone with creation of the proton gradient. The Bacteroides NUO complex is different than in most studied bacteria. In this aim, we will use genetics and biochemical analyses to conclusively identify the electron donor to NUO, determine the importance of NUO and Na+/H+ antiporters in maintaining the essential proton gradient, and determine the contribution of NUO and Na+/H+ antiporters to bacterial fitness in the mammalian gut. In Aim 2, we will study the acquisition and remodeling of the essential respiration component, menaquinone (MK). Most Bacteroides have all the genes necessary for the de novo synthesis of MK; however, certain Bacteroides species lack the primary men genes and must obtain and remodel dietary and/or microbial sources. We will explore unknown features of MK synthesis including how the isoprenoid chain is cleaved and remodeled, how Bacteroides species without the men operon obtain MK precursors, and the dietary and/or microbiota sources of these precursors. In Aim 3, we will study the NrfHA complex, the genes of which are among the most upregulated during nanaerobic growth. We predict NrfHA is an additional terminal electron donor that functions under nanaerobic conditions and donates electrons to both nitrite and nitric oxide (NO), detoxifying these molecules. We will study the regulation of the nrfHA operon revealing transcriptional factors that upregulate genes during nanaerobic growth, study its ability to donate electrons to both nitrite and NO, and determine if this complex allows Bacteroides to reduce host inflammation and better survive in the inflamed gut. The experiments of this proposal will reveal numerous aspects of basic physiology of the Bacteroides that can be translated for human health benefits.