The Molecular Basis of Host Adaptation and Origin of New Mutualisms

有益细菌是植物和动物健康的基础。尽管致病细菌已经得到了密集的科学关注，但推动有益细菌共生进化的过程仍然知之甚少。这个项目将应用分子遗传学、微生物学和进化生物学的技术和概念观点来记录有益共生进化中涉及的遗传过程。该项目将利用一种异常容易处理的实验模型，涉及海洋动物及其共生细菌：短尾乌贼和发光细菌费氏弧菌之间的共生。一些鱼弧菌菌株与鱿鱼和鱼形成终身共生关系，而另一些菌株则在海洋环境中自由生活。利用这种细菌的自然变异，研究人员将比较六个具有不同环境历史和不同初始定植鱿鱼宿主能力的费氏弧菌菌株，以确定与成功的动物定植相关的细菌突变，以及与有益共生相互作用的演变相关的细菌突变。这是第一批实验进化模型之一，也是唯一的自然模型，旨在探索共生微生物有益宿主适应的机制基础。该项目包括对几名研究生和本科生进行跨学科培训，并利用一个引人入胜的模式系统来促进所有教育水平的学生对进化和共生的理解。该项目还将为初中和高中教师开发教育资源，包括在课堂上使用有益微生物的动手实验。

Beneficial bacteria are the foundation of health in both plants and animals. Although disease-causing bacteria have received intensive scientific attention, the processes that drive the evolution of beneficial bacterial symbioses are still poorly understood. This project will apply the techniques and conceptual perspectives of molecular genetics, microbiology and evolutionary biology to document the genetic processes involved in evolution of beneficial symbiosis. The project will make use of an unusually tractable experimental model involving marine animals and their symbiotic bacteria: the symbiosis between bobtail squid and a light-producing bacterium, Vibrio fischeri. Some strains of Vibrio fischeri form life-long symbioses with squid and fish, whereas other strains are free-living in the marine environment. Exploiting the natural variation in this bacterium, the investigators will compare six V. fischeri strains with diverse environmental histories and differing initial capacities for colonization of squid hosts to identify bacterial mutations correlated with successful animal colonization, and with evolution of beneficial symbiotic interactions. This is among the first experimental evolution models, and the only natural model, to explore the mechanistic basis of beneficial host-adaptation in symbiotic microbes. The project includes interdisciplinary training for several graduate and undergraduate students, and capitalizes upon an engaging model system to promote an understanding of evolution and of symbiosis among students at all educational levels. The project will also develop educational resources for middle and high school teachers, including hands-on experiments using beneficial microbes in the classroom.