Light-dependent regulation of coccolithophore host-virus interactions: mechanistic insights and implications for structuring infection in the surface ocean

浮游植物，微观光合藻类，形成海洋食物网的基础，并负责生产地球上近一半的氧气，但占地球生物量的1%。稳定维持高产量与生物量的比率意味着，平均而言，这些生物每周生长、死亡和被替换一次。病毒的捕食性感染已经成为浮游植物种群高死亡率的主要机制。尽管病毒死亡率在构建海洋微生物生态系统中的重要性，但对调节宿主-病毒相互作用的基本机制知之甚少。浮游植物天生依赖于光和光合作用。由于需要宿主资源，因此感染这些生物的病毒也必须基本上依赖于光和光合作用。该项目将探索光与病毒感染之间的关系，以建立一个框架，说明光如何影响海洋表层的病毒感染和浮游植物死亡率。广泛分布的浮游植物种类Emiliania huxleyi，及其相关的病毒，球石病毒，已成为突出的模式系统，调查藻类-病毒的相互作用，由于其生态相关性和集体机制的洞察力，从许多生理，分子，生化，基因组和现场研究。本研究将利用基于细菌培养的研究来阐明光在介导大肠杆菌感染中的作用。huxleyi，特别是解决光是否是病毒感染所必需的，以及确定光调节宿主代谢过程，病毒可以增选成功的感染和生产。然后，这些观察结果将被扩展到自然种群，使用操纵，基于现场的实验，以阐明光在海洋表面结构化感染中所起的作用。该项目为罗格斯大学的本科生和博士后研究人员提供了实践培训。为了促进海洋素养，研究人员将与教育和公共宣传工作人员以及罗非鱼电影有限责任公司合作，根据研究结果和下一代科学标准开发教育视频。这个视频，针对初中，高中和本科生，扩大了一个已经成功的视频系列，通过真实的研究调查突出科学实践。 它将开放获取，并通过现有的连接传播到新泽西科学教师协会，国家科学教师协会，国家海洋教育工作者协会和国家生物教师协会。病毒的捕食性感染是浮游植物种群中观察到的高溶解率的主要机制。作为水生环境中最丰富的生物实体，病毒转化超过四分之一的光合作用固定碳，从而为微生物食物网提供燃料，并缩短碳出口到更高营养水平和深海的路线。尽管病毒引起的死亡率很重要，但其估计值很少被纳入净初级生产力和深层碳输出的全球模型中，部分原因是我们缺乏对调节宿主-病毒相互作用的基本因素的机械理解。对于感染专性光合自养生物的病毒，光和感染过程之间存在固有的和基本的相互作用，以及依赖于病毒复制可能需要的光调节宿主代谢过程。本研究以模式宿主--赫氏爱米利亚藻（Emiliania huxleyi）及其伴生的球石病毒（Coccolithovirus）为研究对象，探讨了以下假设：1）在E. huxleyi中的感染动态; Huxleyi是通过光依赖性过程驱动，特别是光介导病毒进入和复制，以及病毒重定向宿主能量以使病毒复制最大化，和2）光增加病毒衰变，减轻宿主的病毒压力。这种机制，细胞框架，然后将被用来阐明光的作用，在结构化感染的天然颗石藻种群使用操纵现场为基础的实验。鉴于光是海洋中最基本、最容易测量的特征之一，这项工作最终将为全球海洋中病毒感染的生物地球化学影响建模提供背景。

Phytoplankton, microscopic photosynthetic algae, form the basis of marine foodwebs and are responsible for producing nearly half the oxygen on the planet, yet represent 1% of Earth's biomass. Steady-state maintenance of a high production to biomass ratio implies that, on average, these organisms grow, die and are replaced once every week. Predatory infection by viruses has emerged as the primary mechanism responsible for the high mortality rates of phytoplankton populations. Despite the importance of viral mortality in structuring marine microbial ecosystems, little is known about the fundamental mechanisms that regulate host-virus interactions. Phytoplankton are inherently dependent on light and photosynthesis. Given the need for host resources, the viruses that infect these organisms must, therefore, also fundamentally depend on light and photosynthesis. This project will explore the relationship between light and viral infection to develop a framework for how light influences viral infection and phytoplankton mortality in the surface ocean. The widespread phytoplankton species Emiliania huxleyi, and its associated virus, Coccolithovirus, has emerged as the prominent model system for investigating algal-viral interactions due to its ecological relevance and collective mechanistic insight from numerous physiological, molecular, biochemical, genomic, and field studies. Laboratory-based culture studies will be used to elucidate the role light plays in mediating infection in E. huxleyi, specifically addressing whether light is required for viral infection as well as identifying the light-regulated host metabolic processes that viruses may co-opt for successful infection and production. These observations will then be extended to natural populations using manipulative, field-based experiments to elucidate the role light plays in structuring infection in the surface ocean. This project provides hands-on training for a Rutgers University undergraduate student, as well as a postdoctoral researcher. To facilitate ocean literacy, researchers will work with the Education and Public Outreach staff and Tilapia Film, LLC to develop an educational video based on research findings and the Next Generation Science Standards. This video, aimed at middle, high school, and undergraduate students, expands on an already successful video series that highlights scientific practices through real research investigations. It will be open access and disseminated through existing connections to the New Jersey Science Teacher Association, the National Science Teachers Association, the National Marine Educators Association, and the National Biology Teachers Association. Predatory infection by viruses is the primary mechanism responsible for the high lysis rates observed in phytoplankton populations. As the most abundant biological entities in aquatic environments, viruses turn over more than a quarter of the photosynthetically-fixed carbon, thereby fueling microbial foodwebs and short-circuiting carbon export to higher trophic levels and the deep sea. Despite its importance, estimates of viral-induced mortality are rarely included in global models of net primary productivity and deep carbon export, in part because we lack a mechanistic understanding of the fundamental factors that regulate host-virus interactions. For viruses infecting obligate photoautotrophs, there is an inherent and fundamental interaction between light and the infection process, as well as a dependence on light-regulated host metabolic processes that may be required for viral replication. Using the model algal host, Emiliania huxleyi and its associated Coccolithovirus, this project addresses the hypotheses that: 1) infection dynamics in E. huxleyi are driven through light-dependent processes, specifically that light mediates viral entry and replication, and that viruses redirect host energy to maximize viral replication, and 2) light increases viral decay relieving hosts of viral pressure. This mechanistic, cellular framework will then be used to elucidate the role light plays in structuring infection in natural coccolithophore populations using manipulative field-based experiments. Given that light is one of the most fundamental, readily, and easily measured features of the ocean, this work will ultimately provide a context for modeling the biogeochemical impact of viral infection in the global ocean.