Mechanisms Maintaining Cooperation in Rhizobial Populations

维持根瘤菌群体合作的机制

• 批准号: 0645791
• 负责人: Ellen Simms
• 金额: $ 80.92万
• 依托单位: University of California-Berkeley
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2007
• 资助国家: 美国
• 起止时间: 2007-02-01 至 2014-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0645791&HistoricalAwards=false
• 关键词: Mechanisms; Maintaining; Cooperation; Rhizobial; Populations

Cooperation among species, or mutualism, is ubiquitous but perplexing because of the problem of cheaters. Cheaters receive benefits without reciprocating. What prevents them from breaking down a mutualism? Two solutions have been proposed. Under partner choice, choosy partners reward beneficial mutualists and punish cheaters. Under partner fidelity, cheating on a long-term mutualist feeds back to harm the cheater. Scant work has tested these theories empirically. In an ecologically important mutualism, root-nodulating rhizobial bacteria convert atmospheric nitrogen to a plant-available form in exchange for resources produced through photosynthesis by the legume host. However, some rhizobia infect hosts without providing benefit and some ignore hosts altogether. Little is known about the selective forces that prevent these bacteria from spreading. This project will study how selection can promote cooperation in rhizobia. Surveys and manipulative experiments will: (1) characterize rhizobial populations in soil, on roots, and in nodules, (2) document population genetic changes in nodulated rhizobia during infection, (3) test for release of cooperative rhizobia from senescing nodules, and (4) examine partner choice in several legume species.Plants and animals, including humans and our food sources, are critically dependent on beneficial microbes. However, mutualistic microbes can become parasitic. Phenomena such as coral bleaching might be explained by environmental sensitivity of mutualistic microbes. Understanding what factors drive these shifts and how cooperation is maintained helps us understand how to limit the evolution of virulence in human pathogens, improve crop and livestock productivity, and predict and manage responses to environmental change. Research results will be used to enrich classroom learning and public lectures. Students from diverse backgrounds will learn research methods, and graduate students and postdoctoral scholars will learn to mentor undergraduate students.

物种间的合作，或互惠共生，无处不在，但由于骗子的问题而令人困惑。作弊者在没有回报的情况下获得利益。是什么阻止他们打破互惠主义？提出了两种解决方案。在伴侣选择下，挑剔的伴侣奖励互惠互利者，惩罚欺骗者。在伴侣忠诚的情况下，对长期互惠关系的出轨会反过来伤害出轨者。很少有工作对这些理论进行实证检验。在生态上重要的共生关系中，根瘤菌根瘤菌将大气中的氮转化为植物可利用的形式，以换取豆科植物宿主通过光合作用产生的资源。然而，有些根瘤菌感染宿主而不提供益处，有些则完全忽略宿主。人们对阻止这些细菌扩散的选择性力量知之甚少。该项目将研究选择如何促进根瘤菌的合作。调查和操作实验将：(1)表征土壤、根系和根瘤中的根瘤菌种群，(2)记录根瘤菌在感染过程中的种群遗传变化，(3)测试从衰老根瘤中释放合作根瘤菌，(4)研究几种豆科植物的伴侣选择。植物和动物，包括人类和我们的食物来源，都严重依赖于有益微生物。然而，共生微生物可以变成寄生虫。珊瑚白化等现象可以用共生微生物对环境的敏感性来解释。了解驱动这些变化的因素以及如何维持合作有助于我们了解如何限制人类病原体毒力的演变，提高作物和牲畜生产力，以及预测和管理对环境变化的反应。研究成果将用于丰富课堂学习和公开讲座。来自不同背景的学生将学习研究方法，研究生和博士后学者将学习指导本科生。