The evolution and origins of uncooperative rhizobia

共生细菌感染对动植物健康至关重要。然而，据预测这些有益的感染在进化上是不稳定的。帮助宿主的细菌有可能进化成利用宿主的寄生虫。或者，它们可能会转向新的生活史，完全放弃与宿主的互动。这两种进化途径都可能对宿主有害，因为不合作的细菌会传播并接管有益的种群。在这里，在豆科植物根部发现的共生细菌（根瘤菌）将被用来检查有益细菌感染的不稳定性。实地调查、接种试验、实验进化研究和分子分析将(i)评估不合作根瘤菌在野生共生种群中出现的频率，（ii）调查不合作菌株的繁殖成功率，以及（iii）检验关于形成不合作根瘤菌策略的进化力量的假设。共生细菌是生命中一个关键但却鲜为人知的方面。人类和我们的食物来源往往依赖于细菌的合作来维持健康，因此需要研究有害菌株的来源。这项研究将为宿主有益细菌如何以及为什么转变为有害模式提供线索。它将为学生提供培训机会，并将结果纳入课堂活动。

Infection by symbiotic bacteria is critical to plant and animal health. However, these beneficial infections are predicted to be evolutionarily unstable. Bacteria that help hosts can potentially evolve into parasites that exploit hosts. Alternatively, they might shift into novel life histories and abandon host interaction entirely. Both evolutionary pathways can be harmful to hosts, as uncooperative bacteria spread and take over beneficial populations. Here, the symbiotic bacteria (rhizobia) found on legume roots will be used to examine instability of beneficial bacterial infections. Field surveys, inoculation assays, experimental evolution studies and molecular analyses will (i) assess the frequency with which uncooperative rhizobia emerge in wild symbiont populations, (ii) investigate the reproductive success of uncooperative strains, and (iii) test hypotheses about the evolutionary forces that can shape uncooperative rhizobial strategies.Symbiotic bacteria are a key yet poorly understood facet of life. Humans and our food sources often depend upon bacterial cooperation for health, and research is needed to investigate the origins of harmful strains. This research will provide clues about how and why host-beneficial bacteria shift into harmful modes. It will provide training opportunities to students, and results will be incorporated into classroom activities.