Collaborative Research: Elucidating algal host-virus dynamics in different nutrient regimes - mechanistic interactions and biogeochemical impact

合作研究：阐明不同营养状况下藻类宿主病毒的动态 - 机械相互作用和生物地球化学影响

• 批准号: 1537951
• 负责人: Kay Bidle
• 金额: $ 48.16万
• 依托单位: Rutgers University New Brunswick
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2019-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1537951&HistoricalAwards=false
• 关键词: Collaborative; Research; Elucidating; algal; host

Marine phytoplankton, photosynthetic microscopic organisms that float with the oceans currents, account for ~50% of the Earths primary productivity. When there are sufficient nutrients and light to sustain their growth, phytoplankton thrive and produce large-scale blooms in the world oceans that can be seen from Earth-observing satellites. Coccolithophores are arguably one of the most dominant and globally distributed phytoplankton. Their dual ability to produce calcium carbonate cell walls and to use carbon dioxide for photosynthesis make them a key component of the oceanic carbon cycle and marine ecosystems. As such, water column processes that impact the fate of this cellular carbon are of critical importance. Emiliania huxleyi is a globally widespread, cosmopolitan coccolithophore that forms blooms in all but the polar oceans. These blooms are routinely terminated by virus infection (Coccolithoviruses), which results in cell death and the release of organic matter into the upper ocean. At the same time, infection triggers the production and release of a sticky mucus-like gel which serves to aggregate free floating cells (and even viruses) into larger particles that have very high sinking rates into the deep ocean. Hence, viruses play multifaceted roles in determining whether phytoplankton carbon sinks to the deep ocean and is sequestered away from the atmosphere or is recycled in the upper ocean free to exchange with the atmosphere. Ultimately, factors that impact the interactions between phytoplankton cells and viruses are likely to affect the direction of carbon flow in the oceans. This project uses a well-characterized, laboratory-based coccolithophore-virus system (E. huxleyi and Coccolithoviruses) to elucidate the basic mechanisms that underlie host-virus interactions at the levels of adsorption, replication and production. The researchers will manipulate nutrient supply to understand its impact on mechanisms of infection and to better interpret population changes in different oceanic regimes. A key tenet is to investigate the role of mucus-like gels and calcium carbonate cell walls, both of which are produced under nutrient stress, as important first order drivers in host-virus interactions. Experimental work will be integrated into mathematical models as a tool to extrapolate our findings and postulate how, to first order, viruses control the fate of phytoplankton populations in the ocean. Research concepts and findings will be relayed to broader audiences by developing an online educational software tool and web app (via the Rutgers University Mobile App Development group) that focuses on the use of mathematical modeling in marine science. It will be designed to meet national requirements for the Next Generation Science Standards (NGSS) for 15-16 year olds. Students will learn about patterns of ocean productivity, articulate how and why ocean ecosystems are sensitive to environmental change, and understand the role of viruses in ecosystem structure. To ensure large-scale distribution of the app, with a particular aim to reach underrepresented students and to address the NGSS, Rutgers will host workshops to familiarize the teachers with the science, the scientists, and effective use of the app and associated lessons. The investigators will work with external evaluators to assess the effectiveness of these activities and deliverables. Research activities will also be communicated to the general public by interactions with the 'Liquid Living' display at the San Francisco Exploratorium and the annual 'Nautical Night' at the MIT museum in Boston, MA.Phytoplankton are the basis of marine food webs and are responsible for approximately half of global net primary production. As highly abundant infectious entities in the oceans, marine viruses can cause the demise of phytoplankton blooms and drive the release of dissolved and particulate organic matter (DOM and POM), which stimulates microbial activity, facilitates bacterial re-mineralization, enhances nutrient recycling and respiration, as well as short-circuits carbon transport to higher trophic levels. At the same time, enhanced production and release of "sticky" colloidal cellular components, such as transparent exopolymer particles (TEP), during viral lysis can cause particle aggregation and enhance carbon export. As yet, the dynamics of phytoplankton infection by viruses and the balance between these diametrically opposed ecosystem pathways has not been fully characterized under different physicochemical conditions. An enhanced mechanistic and quantitative understanding of host-virus interactions can critically inform and constrain ecosystem models and allow researchers to ascertain and quantify its ecological and biogeochemical impacts on large spatial scales. This collaborative project aims to bridge existing gaps in our mechanistic and quantitative understanding of viruses as agents of phytoplankton mortality and their impact on biogeochemical processes. The ability of ecosystem models to predict carbon flow in marine systems is limited, in part, by a lack of appropriate information regarding the nutrient sensitivity of fundamental infection parameters: viral adsorption rates onto/into hosts, virus replication efficiency and latent period, and the production of infectious viruses and their excretion into the surrounding medium. Using lab-based experiments with a coccolithophore host-virus model system, as well as extensive datasets from virus infected natural coccolithophore blooms in the North Atlantic, this project aims to elucidate the impact of nutrient limitation and host cell fitness on virus infection and to what degree the dependence of viral infection on nutrient supply impacts large scale biogeochemistry and biogeography of a globally significant phytoplankton species. This interdisciplinary approach combines grounded molecular- and flow cytometry-based diagnostic techniques, with the development of a mathematical model of infection, to understand the primary mechanisms underlying observed host-virus dynamics. The investigators will embed the mathematical model of infection dynamics into a global ecosystem model, so we may understand the ecological impact of phytoplankton infection by viruses, and its dependence on nutrient supply, on large spatial scales.

海洋浮游植物是随洋流漂浮的光合微生物，占地球初级生产力的50%左右。当有足够的营养和光照来维持它们的生长时，浮游植物就会茁壮成长，并在世界海洋中产生大规模的水华，这可以从地球观测卫星上看到。球石藻可以说是最具优势和全球分布的浮游植物之一。它们产生碳酸钙细胞壁和利用二氧化碳进行光合作用的双重能力使它们成为海洋碳循环和海洋生态系统的关键组成部分。因此，影响细胞碳命运的水柱过程是至关重要的。埃米利亚·赫胥黎是一种遍布全球的世界性球石藻，除了极地海洋外，它在所有海洋中都能形成大量繁殖。这些藻华通常因病毒感染（球菌病毒）而终止，导致细胞死亡并将有机物释放到上层海洋中。与此同时，感染引发一种黏液状凝胶的产生和释放，这种凝胶可以将自由漂浮的细胞（甚至病毒）聚集成更大的颗粒，这些颗粒在深海中下沉的速度非常快。因此，病毒在决定浮游植物的碳是沉入深海并被隔绝于大气之外，还是在上层海洋中循环并与大气自由交换方面发挥着多方面的作用。最终，影响浮游植物细胞与病毒之间相互作用的因素可能会影响海洋中碳流的方向。本项目利用一个具有良好特征的、基于实验室的球石细胞-病毒系统（赫胥黎E.和球石病毒）来阐明宿主-病毒在吸附、复制和生产水平上相互作用的基本机制。研究人员将操纵营养供应，以了解其对感染机制的影响，并更好地解释不同海洋环境下的种群变化。一个关键的原则是研究黏液样凝胶和碳酸钙细胞壁的作用，两者都是在营养胁迫下产生的，在宿主-病毒相互作用中作为重要的一级驱动因素。实验工作将被整合到数学模型中，作为一种工具来推断我们的发现，并假设病毒如何首先控制海洋中浮游植物种群的命运。研究概念和发现将通过开发在线教育软件工具和网络应用程序（通过罗格斯大学移动应用程序开发小组）传递给更广泛的受众，该软件侧重于在海洋科学中使用数学建模。它的设计将满足国家对15-16岁学生的下一代科学标准（NGSS）的要求。学生将了解海洋生产力的模式，阐明海洋生态系统如何以及为什么对环境变化敏感，并了解病毒在生态系统结构中的作用。为了确保该应用程序的大规模分发，特别针对代表性不足的学生，并解决NGSS问题，罗格斯大学将举办研讨会，让教师熟悉科学、科学家，以及有效使用该应用程序和相关课程。调查人员将与外部评估人员合作，评估这些活动和可交付成果的有效性。研究活动也将通过与旧金山探索博物馆的“液体生活”展览和马萨诸塞州波士顿麻省理工学院博物馆的年度“航海之夜”的互动与公众交流。浮游植物是海洋食物网的基础，约占全球净初级产量的一半。作为海洋中高度丰富的感染性实体，海洋病毒可以导致浮游植物大量繁殖的死亡，并驱动溶解和颗粒有机物（DOM和POM）的释放，从而刺激微生物活动，促进细菌再矿化，增强营养物质的循环和呼吸，以及缩短碳向更高营养水平的运输。同时，在病毒裂解过程中，“粘性”胶体细胞组分（如透明外聚合物颗粒（TEP））的产生和释放增强，可引起颗粒聚集，增强碳输出。迄今为止，在不同的物理化学条件下，浮游植物被病毒感染的动力学以及这两种截然相反的生态系统途径之间的平衡尚未得到充分的表征。加强对宿主-病毒相互作用的机制和定量理解可以为生态系统模型提供重要信息和限制，并使研究人员能够确定和量化其在大空间尺度上的生态和生物地球化学影响。这个合作项目旨在弥合我们对病毒作为浮游植物死亡的媒介及其对生物地球化学过程的影响的机制和定量理解方面的现有差距。生态系统模型预测海洋系统碳流量的能力有限，部分原因是缺乏关于基本感染参数的营养敏感性的适当信息：病毒在宿主上/进入宿主的吸附率、病毒复制效率和潜伏期、感染性病毒的产生及其排泄到周围介质中。利用球石藻宿主-病毒模型系统的实验室实验，以及北大西洋病毒感染天然球石藻华的大量数据集，本项目旨在阐明营养限制和宿主细胞适合度对病毒感染的影响，以及病毒感染对营养供应的依赖在多大程度上影响全球重要浮游植物物种的大尺度生物地球化学和生物地理学。这种跨学科的方法结合了基于分子和流式细胞术的诊断技术，以及感染数学模型的发展，以了解观察到的宿主-病毒动力学的主要机制。研究人员将把感染动力学的数学模型嵌入到全球生态系统模型中，以便在大空间尺度上理解浮游植物感染病毒的生态影响及其对养分供应的依赖。