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

浮游植物是微小的光合作用藻类，构成了海洋食物网的基础，产生了地球上近一半的氧气，但占地球生物量的1%。保持高产量与生物量比率的稳定状态意味着，这些生物体平均每周生长、死亡和更换一次。病毒的捕食性感染已成为造成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很重要，但人们对调节宿主-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。考虑到对寄主资源的需求，感染这些有机体的病毒必须从根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，研究光如何影响表层海洋的病毒感染和浮游植物死亡。大量的生理、分子、生化、基因组和野外研究表明，广泛存在的浮游植物物种埃米利亚尼亚和它的伴生病毒球藻病毒，由于其生态相关性和共同的机理洞察，已经成为研究藻类和病毒相互作用的重要模式系统。基于实验室的培养研究将用于阐明光在介导虎纹伊氏菌感染中的作用，特别是研究光是否是病毒感染所必需的，以及确定病毒可能为成功感染和生产而选择的光调节宿主代谢过程。然后，这些观察将通过基于现场的操纵性实验扩展到自然种群，以阐明光在构建表层海洋感染中所起的作用。该项目为罗格斯大学本科生和博士后研究员提供实践培训。为了促进海洋素养，研究人员将与教育和公共外联工作人员和罗非鱼电影有限责任公司合作，根据研究成果和下一代科学标准制作教育视频。这个视频是针对初中生、高中生和本科生的，在一个已经很成功的系列视频的基础上进行了扩展，该系列视频通过真实的研究调查突出了科学实践。它将开放获取，并通过与新泽西州科学教师协会、全国科学教师协会、全国海洋教育工作者协会和全国生物教师协会的现有联系进行传播。病毒的捕食性感染是浮游植物种群中观察到的高裂解率的主要机制。作为水生环境中最丰富的生物实体，病毒转移了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，并使碳短路出口到更高的营养水平和深海。尽管病毒引起的死亡估计很重要，但净初级生产力和深层碳输出的全球模型很少包括它，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性理解。对于感染专性光自养细胞的病毒来说，光和感染过程之间存在内在的和基本的相互作用，以及对病毒复制所需的光调节宿主代谢过程的依赖。使用模式藻类宿主Emily huxleyi及其相关的球虫病毒，该项目解决了以下假设：1)E.huxleyi中的感染动态是通过依赖光的过程驱动的，特别是光介导病毒的进入和复制，病毒重新引导宿主能量以最大限度地复制病毒，以及2)光增加病毒的衰变，缓解宿主的病毒压力。这个机械性的细胞框架将被用来通过基于现场的操纵性实验来阐明光在构建自然球虫种群感染中所起的作用。鉴于光是海洋最基本、最容易测量的特征之一，这项工作最终将为模拟全球海洋中病毒感染的生物地球化学影响提供一个背景。

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.