Role of hopanoid microbial lipids in a legume:microbe nitrogen-fixing symbiosis

项目摘要 众所周知，细菌细胞壁的成分对宿主的成功是至关重要的 致病微生物和有益微生物的相互作用。而详细的机械信息是 可用于细胞壁成分的子集(即脂多糖(LPS)和 在这些结合中，很少有其他细菌细胞表面分子像 调查过了。细菌类霍普诺正在成为相互作用效率的新决定因素 细菌的子集和它们的真核宿主之间。类胡萝卜素是一种由 各种真核生物相关细菌，包括洋葱伯克氏菌中的人类病原体 Complex和蜡状芽孢杆菌。除了使细菌膜变硬外，类似于真核生物 已知的是，在培养过程中，甾醇类化合物对细菌具有广泛的抗逆性。在自然感染中 上下文，霍帕诺德提供的提高抗逆性的意义，以及霍帕诺德是否 授予其他优势，还没有机械地阐明。 纽曼实验室最近的研究表明，一种特定类别的霍普诺类动物，延长了 含有胞外碳氢化合物尾巴的霍帕诺类化合物，调节共生体的效率 固氮菌重氮慢生根瘤菌与豆科植物寄主的相互作用 Aeschynomene afraspera。我已经确定，延长的类霍普诺数会影响 所有阶段的共生，包括植物根部的初始细菌感染和随后的繁殖 宿主细胞内的细菌共生体。我推测，在这些过程中，延长的类霍普诺德的作用 阶段是促进细菌在非生物应激源下的生长，特别是机械和化学应激 由寄主生态位提供的压力。在我的研究计划中，我建议进一步描述 重氮效率芽孢杆菌-A的扩展霍普诺酮。非洲菊的共生和利用该系统作为模式 更广泛地说，类霍普诺德如何促进真核宿主的持续感染。 在我的博士学位中，我研究了人类组织培养模型中的核肌动蛋白细胞骨架，使用 数量显微镜和生物物理学的方法，以及完成我的研究计划将需要我 来显著扩展我的技能范围。我正在申请K99大奖，以支持我需要的培训 发展必要的研究和非研究技能，以实现我的长期职业目标 在一所R1机构建立一个成功的独立实验室。我希望将各种方法综合在一起 生物物理学、定量显微镜、植物栽培和微生物生理学研究微生物 对寄主的化学和机械环境的反应。我相信我的训练史 使我独一无二地适合占据这个未被研究的研究利基市场，我预计这将产生关键 微生物适应宿主的原则，将广泛适用于许多宿主：微生物系统。

Project Abstract It is well known that components of the bacterial cell wall are crucial to successful host interactions for both pathogenic and beneficial microbes. While detailed mechanistic information is available on the roles of a subset of cell wall components (i.e. lipopolysaccharides (LPS) and peptidoglycan) in these associations, few other bacterial cell surface molecules have been as rigorously investigated. Bacterial hopanoids are emerging as new determinants of the efficiency of the interactions between a subset of bacteria and their eukaryotic hosts. Hopanoids are sterol-like lipids produced by diverse eukaryote-associated bacteria, including the human pathogens in the Burkolderia cepacia complex and Bacillus cereus spp. In addition to rigidifying bacterial membranes, similarly to eukaryotic sterols, hopanoids are known to confer broad stress resistance to bacteria in culture. In native infection contexts, the significance of the increase stress resistance provided by hopanoids, and whether hopanoids confer other advantages, has not been mechanistically clarified. Recent work in the Newman lab has demonstrated that a specific class of hopanoids, extended hopanoids containing an extracellular hydrocarbon tail, regulates the efficiency of the symbiotic interaction between the nitrogen-fixing bacterium Bradyrhizobium diazoefficiens with the legume host Aeschynomene afraspera. I have determined that extended hopanoids affect the progression of the symbiosis at all stages, including the initial bacterial infection of plant roots and subsequent proliferation of bacterial symbionts within host cells. I hypothesize that the role of extended hopanoids during these stages is to enhance bacterial growth under abiotic stressors, specifically the mechanical and chemical pressures provided by the host niche. In my Research Plan, I propose to characterize further the role of extended hopanoids in the B. diazoefficiens-A. afraspera symbiosis and to use this system as a model for how hopanoids facilitate persistent infections of eukaryotic hosts more generally. In my PhD I studied the nuclear actin cytoskeleton in human tissue culture models, using approaches in quantitative microscopy and biophysics, and completing my Research Plan will require me to significantly expand my skill set. I am applying for a K99 award to support the training I need to develop both the research and non-research skills necessary to achieve my long-term career goal of establishing a successful independent laboratory at an R1 institution. I hope to synthesize approaches in biophysics, quantitative microscopy, plant cultivation and microbial physiology to study microbial responses to the chemical and mechanical environments of their hosts. I believe that my training history makes me uniquely suited to occupy this under-studied research niche, which I expect to yield key principles of microbial adaptation to hosts that will be broadly applicable to many host:microbe systems.