The PDIM paradox of M. tuberculosis

项目摘要 结核分枝杆菌（Mtb）已经是20世纪90年代以来全世界传染病死亡率的主要原因。 在过去的几十年里，每年有超过一百万人死亡。这种病原体有一种异常复杂的细胞 壁结构，其外部组件对于与宿主的直接相互作用是重要的， 结构支持和维持小分子和抗生素的疏水屏障。苯硫蜡醇 二真菌蜡酸盐（PDIM）是在Mtb细胞包膜的最外层中发现的脂质。PDIM表格a 渗透屏障，保护细菌免受抗菌化合物的侵害，是重要的毒力因子 来抵御宿主免疫系统 奇怪的是，尽管有这些重要的功能，PDIM在体外是不稳定的，它的损失赋予生长 这一优势导致在实验室培养物中选择自发发生的PDIM阴性克隆。这 影响实验的可靠性、可重复性和结果的解释。PDIM损失导致细胞壁减少 渗透性和毒力衰减，在感染实验中产生误导性结果，药物敏感性 测试和基因操作。为了消除结核病研究中的PDIM偏见，并研究PDIM在结核病研究中的作用， 发病机制和药物耐受性，我们需要适当的筛选和选择工具。 在这项拨款申请中，我们将建立在强大的新的初步结果，以开发强大的PDIM 选择、筛选和清除方案，确定不同Mtb菌株中PDIM损失的倾向， 其对毒力的影响，并旨在研究PDIM群体异质性和丙酸代谢如何影响 感染性和抗生素持久性。

Project Summary Mycobacterium tuberculosis (Mtb) has been the leading cause of infectious disease mortality worldwide for the past few decades with more than 1 million deaths annually. This pathogen has an exceptionally complex cell wall structure, the outer components of which are important for direct interactions with the host, for giving structural support and maintaining a hydrophobic barrier for small molecules and antibiotics. Phthiocerol dimycocerosate (PDIM) is a lipid found in the outer-most layer of the Mtb cell envelope. PDIMs form a permeability barrier, protecting the bacteria from antimicrobial compounds, and are important virulence factors for defense against the host immune system. Paradoxically, despite these important functions, PDIM is dispensable in vitro and its loss confers a growth advantage leading to the selection of spontaneously occurring PDIM negative clones in laboratory cultures. This affects experimental reliability, reproducibly and the interpretation of results. PDIM loss leads to reduced cell wall permeability and virulence attenuation, producing misleading results in infection experiments, drug susceptibility testing and genetic manipulations. To remove PDIM bias from TB research, and to study PDIMs role in pathogenesis and drug tolerance, we need appropriate screening and selection tools. In this grant application we will build on powerful new preliminary results to develop robust PDIM selection, screening and cleanup protocols, determine the propensity of PDIM loss in different Mtb strains and its impact on virulence, and aim to study how PDIM population heterogeneity and propionate metabolism impact infectivity and antibiotic persistence.