Biogeochemical implications of marine phage: Roseophage as a relevant and tractable model

长期以来，原核生物病毒(噬菌体)一直被认为会影响微生物群落组成、营养生物地球化学以及世界海洋中碳的通量和特征。模型估计表明，海洋表层水域每天产生的碳有25%被病毒活动分流到溶解有机物(DOM)池中。通过这一过程，病毒将营养元素从大的生物颗粒(即细菌、藻类)重新分配到生物不活跃(死亡)的颗粒和溶解的有机化合物池中。其中许多化合物含有大量和微量营养素(例如，P、N、Fe)，可以迅速回收到食物链中。虽然我们现在对病毒在营养元素再生中的作用有了更好的(但远未完全)的认识，但我们仍然几乎完全不了解病毒在有机碳再生中的作用，也几乎没有关于病毒在有机碳再生中的作用的数据，也几乎没有关于病毒在有机碳再生中的作用的数据，这些碳随后按大小(例如溶解的与颗粒的)和生物可利用性(不稳定与顽固的)进行分配。如果我们要开发准确的海洋和全球碳模型，了解病毒活动对各种碳库的贡献以及与这一过程相关的速率是绝对必要的。毫无疑问，病毒在全球范围内的影响是由宿主-噬菌体相互作用决定的，但我们对这些相互作用及其对系统过程的量化影响的理解还处于初级阶段。为了解决这些问题，我们必须研究与生态相关的模型系统。为此，该项目专注于感染玫瑰杆菌分支的噬菌体，这是一种数量丰富且具有生物地球化学活性的异养海洋细菌群。尽管谱系成员对元素(特别是碳)的全球循环具有公认的重要性，但我们对感染它们的病毒(“玫瑰体”)、病毒对宿主过程的影响以及这种相互作用对海洋微生物群落其他成员的影响知之甚少。因此，这个项目具有变革性，因为它将利用最近表征的病毒-宿主模型，对真正与生态相关的主要异养浮游细菌谱系进行生物地球化学和分子研究。该项目的总体目标是：(I)研究玫瑰噬菌体的分布、多样性和生产，(Ii)评估玫瑰杆菌细胞裂解衍生DOM的组成和生物利用度，以及(Iii)跟踪海洋表面水微生物群落随后对玫瑰杆菌衍生碳和氮的吸收和新陈代谢。这些目标将通过实验室和现场实验相结合来实现：将开发分子工具，以量化三种不同环境制度(自然多产的开阔海洋制度、近岸到离岸梯度和诱导中附生浮游植物水华)下玫瑰噬菌体产生和玫瑰杆菌死亡的特定比率。PI将在实验室用模型微生物进行试验，具体确定Rosebacter裂解物中碳的特征和生物可利用性。他们将检查自然群落对放射性标记的玫瑰杆菌裂解物的同化率，再加上所释放的DOM的组成、生物利用度和命运的数据，将形成通过微生物食物网的玫瑰杆菌噬菌体C循环模型的基线。最后，对裂解物消费群体的互补代谢组学研究(在实验室和现场)将为微生物如何感知和处理病毒裂解物质提供前所未有的洞察。总的来说，这些数据将提供有关噬菌体与主要海洋细菌谱系的相互作用以及这些相互作用对微生物食物网的后续影响的关键信息。BROADER IMPACTS这项研究的更广泛影响包括对研究生、本科生和预科生的培训，以及促进EPSCoR(刺激竞争研究的实验计划)机构的扩展和多样化。至少3名研究生、14名本科生和4名预科学生将得到资助。该项目的培训方面很高：许多科学活动非常适合本科生和高中生的研究经历。两名新闻学本科生将在实验室获得实践经验，并将科学成果以文章和电子媒体的形式记录下来，传播给普通公众和K-12教育工作者。最后，私人投资机构积极参与旨在招募和留住代表不足的群体进入生物和化学科学研究生课程的计划。

Prokaryotic viruses (phage) have long been hypothesized to influence microbial community composition, nutrient biogeochemistry and both the flux and character of carbon in the world's oceans. Model estimates indicate that 25% of the daily carbon production in marine surface waters is shunted to the dissolved organic matter (DOM) pool by viral activity. Through this process viruses redistribute nutrient elements from large biological particles (i.e., bacteria, algae) into biologically inactive (dead) particulate and dissolved pools of organic compounds. Many of these compounds contain macro- and micronutrients (e.g., P, N, Fe) that can be rapidly recycled back into the food web. While we now have a better (yet far from complete) appreciation of the role of viruses in the regeneration of nutrient elements, we remain almost completely ignorant to, and have almost no data for, the role of viruses in the regeneration of organic carbon, the subsequent partitioning of this carbon by size (e.g. dissolved vs particulate) and bioavailability (labile vs recalcitrant). Understanding the contribution of virus activity to the various carbon pools and the rates associated with this process is an absolute necessity if we are to develop accurate marine and global carbon models.There is little doubt that the global-scale influence of viruses is determined by host-phage interactions, yet our understanding of these interactions and their quantitative effects on system processes is in its infancy. To address these questions, it is imperative that we examine ecologically relevant model systems. To that end, this project focuses on phage that infect the Roseobacter clade, a numerically abundant and biogeochemically active group of heterotrophic marine bacteria. Despite the recognized importance of lineage members to the global cycling of elements (particularly carbon), we know little of the viruses ("roseophage") that infect them, the influence viruses have on host processes and the effects of this interaction on other members of the marine microbial community. As such this project is transformative in that it will exploit recently characterized virus-host models for biogeochemical and molecular studies of a major heterotrophic bacterioplankton lineage that is truly ecologically relevant. The overall objectives of the project are to: (i) examine the distribution, diversity and production of roseophage, (ii) assess the composition and bioavailability of Roseobacter cell lysis-derived DOM and (iii) to track the subsequent uptake and metabolism of Roseobacter-derived carbon and nitrogen by marine surface water microbial communities. These objectives will be achieved through a combination of lab and field-based experiments: molecular tools will be developed to quantify specific rates of roseophage production and Roseobacter mortality under three different environmental regimes (a naturally productive open ocean regime, a near shore to off-shore gradient and induced phytoplankton blooms from mesocosms). The PIs will specifically determine the character and biological availability of carbon from lysates of Roseobacter in lab trials with model microbes. They will examine the rates of assimilation of radiolabeled Roseobacter lysate by natural communities which, when coupled with data on the composition, bioavailability and fate of the DOM released, will form the baseline for a model of Roseobacter-phage C-cycling through the microbial foodweb. Finally, complementary metabolomics studies of lysate consuming populations (in the lab and field) will provide unprecedented insight into how microbes perceive and process viral-lysed material. Collectively, these data will provide critical information on the interplay of phage with a major marine bacterial lineage and the ensuing influence these interactions have on microbial food webs.BROADER IMPACTSThe broader impacts of this study include training of graduate, undergraduate and precollegiate students as well as facilitation of outreach and diversification at an EPSCoR (Experimental Program to Stimulate Competitive Research) institution. At least 3 graduate, 14 undergraduate, and 4 precollegiate students will be supported. The training aspects of the project are high: many of the scientific activities are ideally suited for undergraduates and upper-level high school students research experiences. Two undergraduate journalism students will receive hand-on experiences in the lab and document the scientific efforts as articles and electronic media for dissemination to the general public and K-12 educators. Finally, the PIs are actively engaged in programs designed to recruit and retain under- represented groups into graduate programs in biological and chemical sciences.