CAREER: The molecular basis of abortive symbiosis

这项工作的总体目标是确定分子机制，以确定给定的细菌菌株对其生活的生物体是有害还是有益。根瘤菌是一种已知的土壤细菌，通过向豆科植物提供富含氮的营养物质，对它们大有裨益。根瘤菌具有重要的农业意义，因为它们大大减少了大豆和苜蓿等豆科作物对合成肥料的需求。这个项目研究自然产生的根瘤菌菌株，它们在一些豆科植物上表现得像病原体，在另一些豆科植物上表现得像有益的共生体。这种结果的变化是由一组有限的基因决定的，这些基因已被检测到，但尚未完全测序。这些基因定义了一个重要但神秘的生物过程，决定了根瘤菌是对植物有害还是有益。研究人员正在使用分子水平的分析来确定由这些基因控制的精确生化过程。研究目标与一项教育计划相结合，该计划将允许本科生和高中生参与发现更多这些决定结果的基因，通过户外收集活动和基于实验室的细菌分离分子分析相结合。该项目将支持对高中生、本科生、研究生和博士后的培训，并将直接为开发利用根瘤菌提高作物生产力的更有效策略提供信息。在更基本的层面上，它将使我们更清楚地认识到，密切相关的细菌可能对它们所寄生的植物或动物产生截然不同的影响。

The overall goal of this work is to identify molecular mechanisms that determine whether a given bacterial strain will be harmful or beneficial to the organism in which it lives. Rhizobia are soil bacteria that are known to greatly benefit plants in the legume family by providing them with nitrogen-rich nutrients. Rhizobia are of great agricultural importance, since they dramatically reduce the need for synthetic fertilizers on legume crops such as soybean and alfalfa. This project investgates naturally occurring strains of rhizobia that behave like pathogens on some legume species, and like beneficial symbionts on others. This variation in outcome is dictated by a limited set of genes that have been detected but not fully sequenced. These genes define an important but mysterious biological process that determines whether rhizobia will harm or help the plants that harbor them. The investigators are using molecular-level analysis to define the precise biochemical process that is governed by these genes. The research goals are integrated with an educational plan that will allow undergraduate and high school students to participate in the discovery of more of these outcome-determining genes, through a combination of outdoor collection activities and laboratory-based molecular analysis of bacterial isolates. The project will support the training of high school, undergraduate, graduate, and postdoctoral students and will inform directly the development of more effective strategies for using rhizobia to enhance crop productivity. At a more fundamental level, it will result in a clearer understanding of how closely related bacteria may have radically different effects on the plants or animals in which they reside.