MOLECULAR MECHANISMS OF X. NEMATOPHILA-NEMATODE INTERACT

描述（由申请人提供）：我们研究的长期目标是阐明介导宿主-微生物相互作用的分子机制，并了解微生物过程如何影响这些关系的结果。我们在这些研究中使用的模型细菌是嗜线虫Xenorhabdus nematophila，它既是线虫的共生菌，也是昆虫的病原体，因此是理解这两种关系的绝佳模型。本课题主要研究嗜线虫线虫与线虫之间的相互关系，并对我们实验室在嗜线虫线虫发病机制方面的单独资助工作进行补充。研究嗜线虫线虫和它的线虫宿主的相互作用将扩大我们对动物如何进化和维持与它们的微生物群的特定和依赖关系的理解。本提案的具体目标是针对我们已经确定的几个殖民起始因素的遗传和生物化学特征，以及它们之间的相互作用。特异性目标1将验证我们的假设，即膜定位定殖因子在粘附线虫细胞，金属运输和/或信号转导中起作用。这些研究结果将阐明Nil（线虫肠道定位）蛋白在定植事件中的作用，揭示革兰氏阴性病原体的Nil同源物在启动感染中的可能功能，并进一步了解介导宿主范围特异性的分子机制。特异性目标2旨在剖析定植所需的两个调节因子，一个sigma因子和一个调节RNA的功能。这些实验将深入了解嗜线虫线虫在定植过程中感知到的信号，进一步定义定植特异性调控，并扩展我们对细菌自然生态中普遍存在的转录因子作用的认识。

DESCRIPTION (provided by the applicant): The long-term goal of our research is to elucidate molecular mechanisms mediating host-microbe interactions and to learn how microbial processes affect the outcome of these relationships. The model bacterium we use for these studies is Xenorhabdus nematophila, which is both a mutualist (of nematodes) and a pathogen (of insects), and therefore an excellent model to understand both types of relationships. This proposal focuses on the mutualism between X. nematophila and the nematode and complements separately funded work in our lab on X. nematophila pathogenesis. Examining the mutualistic interactions of X. nematophila and its nematode host will expand our understanding of how animals evolve and maintain specific and dependent relationships with their micro-flora. The specific aims of this proposal are geared toward genetically and biochemically characterizing several of the colonization initiation factors we have identified, as well as their interactions with each other. Specific Aim 1 will test our hypotheses that membrane-localized colonization factors function in adherence to nematode cells, metal transport, and/or signal transduction. The results of these studies will elucidate the roles of Nil (nematode intestine localization) proteins in colonization events, shed light on the possible functions of Nil homologs of gram-negative pathogens in initiating infections, and further our understanding of molecular mechanisms mediating host-range specificity. Specific Aim 2 is designed to dissect the functions of two regulators required for colonization, a sigma factor and a regulatory RNA. These experiments will yield insight into the signals perceived by X. nematophila during colonization, further define a colonization-specific regulon, and expand our knowledge of the role of a ubiquitous transcription factor in the natural ecology of a bacterium.