Collaborative Research: Development, Structure and Function of the Bacterial Symbiont Colonization Site in Steinernematid Nematodes

大多数孩子被教导细菌（微生物）会使他们生病，事实上，有些孩子会。然而，动物和微生物之间更常见的自然关系是互惠互利的，因为微生物对动物的正常发育、营养和免疫是绝对必要的。在这些关联中，微生物通常在动物身上或动物体内的离散位置定植。关于这些定植地点的独特物理性质，或者有益的动物-微生物关系是如何形成和维持的，目前还知之甚少。众所周知，这些过程依赖于动物与微生物之间的交流，这种交流既包括远距离交换的化学信号，也包括通过直接物理接触传递的信号。对于信号的特性，它们是如何产生的，在哪里产生的，它们是如何被识别的，以及它们对每个伴侣的调解作用，仍然缺乏基本的理解。为了开始解决这些问题，拟议的研究集中在一种新的动物-微生物共生模式上，即一种小型的、居住在土壤中的线虫（蛔虫）和与之相关的有益细菌（共生体）之间的共生关系。细菌共生体生活在线虫肠道内的特定囊泡（容器）中，是唯一能够居住在该位置并与线虫建立关系的微生物；换句话说，它是唯一一种能够与线虫正确沟通并实现互利关系的微生物。本研究将分析线虫肠道囊泡的形态和发育特征，以更好地了解定植过程。提出的研究还将探索关于化学信号和物理相互作用的新假设，这些相互作用发生在线虫和共生体之间，以及这些相互作用如何影响每个生物体的生理。此外，拟议的研究将解决这种亲密的动物-微生物关系如何演变的问题。本提案的具体目标是利用显微镜，生物化学和微生物遗传学来表征线虫和共生体之间相互作用的结构和发展，以及每个伙伴如何促进这种关系。所研究的模型系统很容易在实验室中进行研究。参与这项合作研究的三个实验室各自提供拟议研究所需的不同专业知识。这些实验室将共同：1)使用显微镜和生物化学分析线虫肠道区域与微生物共生体相互作用的物理方面；2)比较不同线虫的肠道结构，了解与共生体特异性相互作用的能力是如何进化的；3)研究与共生体相互作用的肠道区域如何发育，共生体如何影响这一发育；4)利用生物化学和遗传学表征线虫和共生体之间交换的化学信号。这个模型系统非常适合于教育，因为它与农业、医学和基础研究以及多学科的观点有着广泛的相关性。一个未被充分代表的少数族裔本科生为初步研究做出了贡献，每个实验室将继续培养和教育来自不同背景的学生。将举行一次讲习班，其中包括通过这项研究开发的数据和技术。最后，这项研究将加强作为美国国家科学基金会资助的威斯康星大学麦迪逊分校“K through Infinity”项目的一部分开发的K-12教学工具。

Most children are taught that germs (microbes) will make them sick, and indeed, some can. However, the more common natural relationship between animals and microbes is mutually beneficial (mutualistic) since microbes are absolutely necessary for normal animal development, nutrition, and immunity. In these associations microbes typically colonize discrete locations on or within the animal. Little is as yet understood regarding the distinct physical nature of such colonization sites, or how beneficial animal-microbe associations are formed and maintained. It is known that these processes rely on animal-microbe communication that can involve chemical signals exchanged from a distance, as well as signaling through direct physical contact. Still lacking is a fundamental understanding of the identities of signals, how and where they are produced, how they are recognized, and the effects they mediate in each partner. To begin to address these questions, the proposed research focuses on an emerging model of animal-microbe mutualism between a small, soil-dwelling nematode (roundworm) and the beneficial bacterium (symbiont) with which it associates. The bacterial symbiont lives in a specific vesicle (receptacle) within the intestine of the nematode, and is the only microbe capable of residing at this location and establishing a relationship with the nematode; in other words, it is the only microbe that can correctly communicate with the nematode to achieve a mutually beneficial relationship. In this study the morphological and developmental features of the nematode intestinal vesicle will be analyzed to better understand the colonization process. The proposed research will also explore new hypotheses regarding the chemical signals and the physical interactions that occur between the nematode and the symbiont and how these interactions might affect the physiology of each organism. Furthermore, the proposed research will address questions of how such intimate animal-microbe associations evolve.The specific goal of this proposal is to characterize, using microscopy, biochemistry, and microbial genetics, the structure and development of the interaction between the nematode and the symbiont and how each partner contributes to this relationship. The model system being studied is easily studied in the laboratory. The three labs involved in this collaborative research are each contributing distinct expertise required for the proposed studies. Together these labs will:1) Analyze, using microscopy and biochemistry, the physical aspects of the nematode intestinal region that interacts with the microbial symbiont;2) Compare the intestinal structures of different nematodes to understand how the ability to specifically interact with the symbiont evolved;3) Study how the intestinal region that interacts with the symbiont develops, and how the symbiont affects this development; and4) Characterize, using biochemistry and genetics, the chemical signals exchanged between the nematode and the symbiont.This model system is well suited for education because of its broad relevance to agricultural, medical, and basic research and multiple disciplinary perspectives. An underrepresented minority undergraduate has contributed to preliminary research, and each lab will continue to train and educate students from diverse backgrounds. A workshop will be held that includes data and techniques developed through this research. Finally, this study will enhance a K-12 teaching tool developed as part of the NSF-funded K through Infinity program at UW-Madison.