CAREER: Novel Determinants of Motility and Chemotaxis in Sinorhizobium meliloti

职业生涯：苜蓿中华根瘤菌运动性和趋化性的新决定因素

• 批准号: 1253234
• 负责人: Birgit Scharf
• 金额: $ 70.39万
• 依托单位: Virginia Polytechnic Institute and State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2019-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1253234&HistoricalAwards=false
• 关键词: CAREER; Novel; Determinants; Motility; Chemotaxis

Nitrogen is the most limiting nutrient for plant growth. While chemically synthesized inorganic nitrogen fertilizers are effective in increasing crop yields, they are costly and also have a negative impact on the environment, especially on aquatic ecosystems. In contrast, sustainable agriculture relies on biological nitrogen fixation as an economically attractive and ecologically viable source of new nitrogen. The conversion of molecular nitrogen into ammonia is performed by bacteria (Rhizobia) that live in symbiosis with leguminous plants such as peas, soy beans, and alfalfa. The research will be carried out using the symbiotic model system, the nitrogen-fixing soil bacterium Sinorhizobium meliloti (S. meliloti). The process of chemotaxis enables motile rhizobia to preferentially move in the soil towards host plant roots and supports efficient interaction between symbiosis partners. Many motile bacteria are propelled by means of rotating flagella, driven by a powerful, self-assembling nanomachine. The unique flagellar motor and the specially adapted chemotaxis system of S. meliloti make cells more efficient at maneuvering in the viscous soil environment, leading to better survival and optimal interaction with their host plant alfalfa. Previous research uncovered several novel molecular mechanisms governing chemotactic responses and motility in S. meliloti, thereby setting the stage for an in-depth analysis of the underlying molecular events. The overarching goal of this project is to analyze the specific adaptations that occurred in S. meliloti motility and chemotaxis due to the soil habitat and communication with its plant host. The first objective of the research analyzes the roles of two novel proteins in the response of S. meliloti to quickly changing environmental signals, which is essential for bacterial survival. The second objective determines the cellular concentrations and enzymatic activities of key chemotaxis components, allowing prediction of bacterial behavior in the interaction with alfalfa crop. The third objective will identify the function of newly discovered flagellar motor components in facilitating effective movement of S. meliloti in the soil and towards symbiosis partners. This research will lead to the discovery of significant bacterial properties and impact current understanding of how bacterial symbionts respond to plant signals and efficiently move through soil.Broader Impacts The project directly benefits future agricultural and environmental issues for society. By enhancing understanding of the cues that bacterial symbionts use to efficiently interact with their host crop, the research will impact biological nitrogen fixation and thus crop yields and reduce the use of detrimental synthetic fertilizers. The project will also vertically integrate research activities with educational activities through the development of an undergraduate classroom exercise addressing currently open research questions, which will transform into scientific discoveries in the research laboratory. The existing, successful outreach program of the Microbiology Club of Virginia Tech will be expanded to rural, underdeveloped communities of Appalachia. Outreach activities in the form of interactive lectures and hands-on activities will promote scientific awareness across the educational spectrum, including a local 4-H Agricultural Club and rural elementary schools. Studies of motility and chemotaxis can be demonstrated easily and will allow the development of innovative, inquiry-based microbiology lessons with High School science teachers, a valuable strategy for effective learning. Collaboration with Novozymes? BioAgricultural Group will give Virginia Tech students the opportunity not only to experience basic research approaches at the university and applied research in industry through merged collaborative training programs, but also to increase their chances for recruitment into professional careers. Overall, this project integrates research and education through the fusion of classroom and laboratory research, hands-on outreach activities in rural communities, and internships in industry, which will promote student engagement and transform student learning and will permanently stimulate student's interest in science.

氮素是植物生长最受限制的养分。虽然化学合成的无机氮肥在提高作物产量方面是有效的，但它们的成本很高，而且对环境，特别是对水生生态系统也有负面影响。相比之下，可持续农业依赖于生物固氮，作为一种经济上有吸引力和生态上可行的新氮源。分子氮转化为氨是由与豆科植物共生的细菌(根瘤菌)完成的，如豌豆、大豆和紫花苜蓿。本研究将利用共生模式系统--土壤固氮细菌苜蓿中华根瘤菌(Sinorhizobium Meliloti(S.Meliloti))进行研究。趋化性的过程使可移动的根瘤菌能够优先在土壤中向宿主植物的根移动，并支持共生伙伴之间的有效相互作用。许多可移动的细菌是通过旋转的鞭毛推动的，由一个强大的、自组装的纳米机器驱动。紫花苜蓿独特的鞭毛马达和特殊适应的趋化系统使细胞在粘性土壤环境中更有效地移动，导致更好的生存和与寄主紫花苜蓿的最佳相互作用。以前的研究发现了几种控制苜蓿趋化反应和运动性的新的分子机制，从而为深入分析潜在的分子事件奠定了基础。本项目的总体目标是分析由于土壤生境和与植物寄主的沟通而发生的对草地早熟禾运动性和趋化性的特殊适应。这项研究的第一个目标是分析两种新的蛋白质在苜蓿链霉菌对快速变化的环境信号的反应中所起的作用，环境信号对细菌的生存至关重要。第二个目标确定了关键趋化成分的细胞浓度和酶活性，从而能够预测细菌在与紫花苜蓿作物相互作用中的行为。第三个目标将确定新发现的鞭毛马达成分在促进苜蓿根结线虫在土壤中有效移动和向共生伙伴移动方面的功能。这项研究将导致发现重要的细菌特性，并影响目前对细菌共生体如何响应植物信号并在土壤中高效移动的理解。广泛的影响该项目直接造福于未来的农业和社会环境问题。通过加强对细菌共生体用于与宿主作物有效互动的线索的理解，这项研究将影响生物固氮，从而影响作物产量，并减少有害合成肥料的使用。该项目还将通过制定一项本科生课堂练习，将研究活动与教育活动垂直结合起来，解决目前悬而未决的研究问题，这些问题将转化为研究实验室的科学发现。弗吉尼亚理工大学微生物俱乐部现有的、成功的推广计划将扩展到阿巴拉契亚地区欠发达的农村社区。以互动讲座和实践活动的形式开展的外联活动将提高教育领域的科学意识，包括当地的4-H农业俱乐部和农村小学。对运动性和趋化性的研究可以很容易地证明，并将允许与高中科学教师一起开发创新的、基于探究的微生物学课程，这是有效学习的一个有价值的策略。与Novozymes合作？生物农业集团将为弗吉尼亚理工大学的学生提供机会，不仅可以通过合并的合作培训计划体验大学的基础研究方法和工业应用研究，还可以增加他们进入专业职业生涯的机会。总体而言，该项目通过融合课堂和实验室研究、农村社区实践推广活动和工业实习来整合研究和教育，这将促进学生参与并改变学生的学习，并将永久激发学生对科学的兴趣。

项目成果

Cellular Stoichiometry of Chemotaxis Proteins in Sinorhizobium meliloti

• DOI: 10.1128/jb.00141-20
• 发表时间: 2020-07-01
• 期刊: JOURNAL OF BACTERIOLOGY
• 影响因子: 3.2
• 作者: Arapov, Timofey D.;Saldana, Rafael Castanda;Scharf, Birgit E.
• 通讯作者: Scharf, Birgit E.