Collaborative Research: Lipid lubrication of oceanic carbon and sulfur biogeochemistry via a host-virus chemical arms race

知识价值：尽管病毒在塑造海洋微生物生态系统方面至关重要，但人们对介导浮游植物-病毒相互作用的分子机制知之甚少。因此，我们目前缺乏生物标志物来量化海洋中活跃的病毒感染，这严重阻碍了我们对其生态和生物地球化学影响的理解。球石藻是一种世界性的单细胞光自养生物，其方解石骨架约占海洋CaCO3总产量的三分之一。赫胥黎氏杆菌每年春季在北大西洋形成大规模的繁殖，被含有球肠炎病毒的巨大双链DNA裂解感染并终止。研究发现，赫胥黎肠杆菌的溶性病毒感染会激活宿主的程序性细胞死亡（PCD）机制，这表明病毒采用了一种复杂的、共同进化的？军备竞赛吗?介导宿主-病毒相互作用。研究人员最近证明，病毒鞘糖脂（vGSLs）来源于鞘脂生物合成基因的意外集群，这是一种在病毒基因组中从未描述过的途径，在促进赫胥黎肠杆菌感染中起着至关重要的功能作用。在北大西洋和挪威峡湾观察到的vgsl进一步表明，它们可能是一种新的、诊断性的球石藻群体病毒感染的生物标志物。同时，vGSLs和一种独特的保护性802脂质的发现表明，宿主-病毒共同进化的化学军备竞赛在调节病毒感染和润滑C和上层海洋生物地球化学通量方面起着关键作用。本项目的重点是阐明vGSLs（和其他极性脂质）与全球碳和硫循环之间的分子、生态和生物地球化学联系。研究小组提出了一种多管齐下的方法，结合了一套基于实验室的机制研究，使用了几个触觉病毒模型系统，以及在东北大西洋进行的观察研究和操作现场实验。利用这些诊断标记，他们将记录天然球石藻种群的活跃病毒感染，并将其与一套海洋学测量相结合，以量化病毒感染（通过vGSLs）如何影响细胞命运、溶解有机碳（DOC）池、特定有机碳（POC）和无机碳（PIC）的垂直输出；如碳酸钙，CaCO3)（以及相关的烯酮脂质生物标志物和病毒及其宿主的遗传特征）和上层海洋硫循环（通过二甲硫[DMS]和其他生物源硫化合物的循环）。此外，鉴于它们是病毒独有的，他们提出，vGSLs可以用来追踪病毒衍生碳的流动，并提供定量的见解。病毒分流?这使得固定碳从更高的营养水平和深海中转移出来。这项研究的首要假设是，vGSLs是上层海洋的基石分子，它促进了大规模的病毒感染，从而在机械上起到了润滑作用。海洋中碳和硫的生物地球化学通量。广泛影响：本研究融合了生理学、分子生物学、生物化学、病毒学和脂质化学的概念，以及海洋学和生物地球化学，从而为不同教育背景的研究人员提供了一个互动和发展的机会。本项目为博士后、研究生和本科生的发展提供了良好的实践训练。该研究为机构间交流提供了资源和机会，并建立在现有的国家和国际合作基础上，并将促进新的合作。pi将与COSEE合作，现在和？网络化的海洋世界？通过将科学研究与K-12教育工作者和公众观众结合起来，提高海洋素养。该项目的一个重要组成部分是使海上科学家与课堂上的学生和公众接触。因此，这个项目包含了几个具体的策略，包括：(1)在海上发布网络/视频博客；(2)聘请一名自由摄像师在前往东北大西洋的游轮上收集多媒体内容，这些内容将用于游轮后的各种交付成果；(3)生产？海洋凝视?播客，让公众可以看到，听到和触摸海洋，并通过介绍正在进行的海洋学研究和采访海洋学家来解开它的一些秘密；(4)将研究活动与正在进行的K-12教师研讨会结合起来，作为海洋活动、资源和教育计划的一部分，并通过与海女孩小学（Sea girl， NJ）的科学/技术教师劳拉·邓巴（Laura Dunbar）的互动。

Intellectual Merit: Despite the critical importance of viruses in shaping marine microbial ecosystems, very little is known about the molecular mechanisms mediating phytoplankton-virus interactions. As a consequence, we currently lack biomarkers to quantify active viral infection in the oceans, significantly hindering our understanding of its ecological and biogeochemical impacts. The coccolithophore Emiliania huxleyi (Prymnesiophyceae, Haptophyte) is a cosmopolitan unicellular photoautotroph whose calcite skeletons account for about a third of the total marine CaCO3 production. E. huxleyi forms massive annual spring blooms in the North Atlantic that are infected and terminated by lytic, giant double-stranded DNA containing coccolithoviruses. Findings that lytic viral infection of E. huxleyi recruits the hosts programmed cell death (PCD) machinery demonstrate that viruses employ a sophisticated, co-evolutionary ?arms race? in mediating host-virus interactions. The investigators recently demonstrated that viral glycosphingolipids (vGSLs), derived from unexpected cluster of sphingolipid biosynthetic genes, a pathway never before described in a viral genome, play a crucial functional role in facilitating infection of E. huxleyi. The observations of vGSLs in the North Atlantic and Norwegian fjords further suggest that they may be novel, diagnostic biomarkers for viral infection of coccolithophore populations. At the same time, the discovery of vGSLs and a distinct, protective 802 lipid argues that a host-virus, co evolutionary chemical arms race plays a pivotal role in regulating viral infection and in lubricating upper ocean biogeochemical fluxes of C and S.The focus of this project is to elucidate the molecular, ecological, and biogeochemical links between vGSLs (and other polar lipids) and the global cycles of carbon and sulfur. The team of investigators proposes a multi-pronged approach combing a suite of lab-based, mechanistic studies using several haptophyte-virus model systems along with observational studies and manipulative field-based experiments the Northeast Atlantic. Using these diagnostic markers, they will document active viral infection of natural coccolithophore populations and couple it with a suite of oceanographic measurements in order to quantify how viral infection (via vGSLs) influences cell fate, the dissolved organic carbon (DOC) pool, vertical export of particular organic (POC) and inorganic carbon (PIC; as calcium carbonate, CaCO3) (along with associated alkenone lipid biomarkers and genetic signatures of viruses and their hosts) and the upper ocean sulfur cycle (via the cycling of dimethylsulfide [DMS] and other biogenic sulfur compounds). Furthermore, given they are unique to viruses, they propose that vGSLs can be used to trace the flow of virally-derived carbon and provide quantitative insights into a ?viral shunt? that diverts fixed carbon from higher trophic levels and the deep sea. The overarching hypothesis for this study is that vGSLs are cornerstone molecules in the upper ocean, which facilitate viral infection on massive scales and thereby mechanistically ?lubricate? the biogeochemical fluxes of C and S in the ocean.Broader Impact: This research blends concepts in physiology, molecular biology, biochemistry, viriology and lipid chemistry, with oceanography and biogeochemistry, thereby providing an opportunity whereby researchers with different educational backgrounds can interact and develop. This project provides excellent hands-on training for development of postdocs, graduate students and undergraduate students. The research provides resources and opportunities for inter-institutional exchange Rutgers-WHOI-College of Charleston and builds both on established national and international collaborations and will foster new ones. The PIs will work with COSEE NOW and ?Networked Ocean World? to increase ocean literacy by integrating scientific research with K-12 educators and public audiences. An important component of this project is to bring scientists at sea in touch with classroom students and the general public. As such, the project incorporates several concrete strategies, including: (1) posting web/video blogs from sea; (2) incorporating a freelance videographer to collect multimedia content on a cruise to the Northeast Atlantic, which will be used in diverse post-cruise deliverables; (3) producing ?Ocean Gazing? podcasts so the general public can look at, listen to and touch the ocean and unpack some of its secrets by presenting ongoing oceanographic research and interviewing oceanographers; and (4) integrating the research activities with ongoing K-12 teacher workshops as part of the Marine Activities, Resources and Education program and through interactions with Laura Dunbar, a Science/Technology teacher at Sea Girt Elementary School (Sea Girt, NJ).