CAREER: Integrating microbiology and population genetics through experimentation with the origins of a microbial mutualism

本研究将研究两种互利微生物的进化。长期以来，人类一直被那些似乎互相帮助的物种所吸引，比如传粉者和开花植物之间的相互作用，或者我们的身体和栖息在它们体内的微生物之间的相互作用。因为这些物种相互影响繁衍的能力，我们期望看到一些跨物种进化的协调，因为每个物种都适应另一个物种施加的变化。一些突变应该只有在共同进化的伴侣存在的情况下才有益。然而，我们不知道这些相互变化发生的频率，因为我们经常无法观察到它们发生的过程，而且在许多物种中，很难确定哪些变化是对伴侣物种的反应，哪些是对环境其他特征的适应。这项研究将通过观察微生物系统中这些相互作用的演变来回答这些问题。这项研究还将开发一个关于微生物进化的主动学习模块，用于普通本科微生物学课程，并为本科生开发两门基于探究的课程。在这些课程中，本科生将测试在进化过程中发生的突变对种群在有无互惠共生的情况下繁衍能力的影响，使他们能够以综合的方式学习进化、微生物生态学和遗传学的基本概念。该实验将包括Hildenborough普通脱硫弧菌和maripaludis古菌甲烷球菌的两种细菌群落，以及单种对照种群。复制社区将进化超过3000代。这种共同进化的共生关系的群体遗传学将通过在几个时间间隔对每个物种的基因组进行测序来确定。种群对生物环境的适应水平将通过比较种群与过去和未来的互惠主义者的适应性，通过将感兴趣的突变转移到祖先菌株中，以及通过沿着主要血统重建所有中间物种并测试它们在有无互惠主义者的情况下的适应性来确定。

This research will study the evolution of two mutually-beneficial microorganisms. Humankind has long been captivated by species that seem to help each other out, such as interactions between pollinators and flowering plants or our bodies and the microorganisms that inhabit them. Because such species affect each other's ability to flourish, we expect to see some coordination of evolution across species as each adapts to the changes imposed by the other. Some mutations should only be beneficial in the presence of the coevolving partner. However, we do not know how often these reciprocal changes occur because we often cannot observe them as they happen and in many species it is difficult to determine which changes were a response to a partner species and which were adaptations to other features of their environment. This research will answer these questions by observing these interactions evolve in a microbial system. The research will also result in the development of an active-learning module on microbial evolution to be used in general undergraduate microbiology courses and the development of two inquiry-based courses for undergraduates. In these courses undergraduates will test the effects of mutations that occurred during evolution on the ability of populations to flourish with or without mutualism, allowing them to learn fundamental concepts of evolution and microbial ecology and genetics in an integrated manner. The experiment will consist of a two-species community of the bacteria Desulfovibrio vulgaris Hildenborough and the archaeon Methanococcus maripaludis, along with single-species control populations. Replicate communities will evolve over 3000 generations. The population genetics of this coevoling mutualism will be determined by sequencing the genomes of each species at several time intervals. The level of adaptation of populations to the biotic environment will be determined by comparing the fitness of populations with past and future mutualists, by moving mutations of interest into ancestoral strains, and by reconstructing all intermediates along the main line of descent and testing their fitness with and without a mutualist partner.