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调节宿主-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。我们用于这些研究的模式细菌是嗜线虫杆菌，它既是(线虫的)互助者，也是(昆虫的)病原体，因此是理解这两种关系的极好模型。本研究的重点是研究嗜线虫与线虫之间的互惠关系，补充我们实验室单独资助的嗜线虫致病机理研究工作。研究嗜线虫与其线虫宿主的互惠作用将扩大我们对动物如何进化以及与其微生物区系保持特定和依赖关系的理解。这项提案的具体目标是从遗传学和生物化学的角度表征我们已经确定的几种定居启动因素，以及它们之间的相互作用。具体目标1将检验我们的假设，即膜定位的定植因子在粘连线虫细胞、金属运输和/或信号转导中发挥作用。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，阐明革兰氏阴性病原菌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。具体目标2旨在剖析定殖所需的两种调节因子--西格玛因子和调节RNA的功能。这些实验将深入了解嗜线虫在定殖过程中感受到的信号，进一步定义定殖特异的调节基因，并扩大我们对普遍存在的转录因子在细菌自然生态中的作用的知识。

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.