Collaborative Research: Viral induced chemotaxis mediating cross-trophic microbial interactions and carbon flux

海洋表层水中漂浮的光合微生物完成了全球近一半的碳(C)固定，既支持了海洋食物网，又降低了大气中的二氧化碳（CO2）水平。海洋生态系统中碳的命运是由高度互联的浮游生物食物网中无数个体的相互作用控制的，这种相互作用的复杂性阻碍了对全球碳循环的预测性理解。化学线索控制着微生物的相互作用，在感染期间，海洋病毒操纵浮游植物和细菌的代谢，促进溶解的有机物从感染细胞中释放出来。本研究旨在确定完整、受感染的浮游植物的病毒代谢重编程和有机物释放如何影响微生物相互作用和C循环。该项目的跨学科、协作性质将使两名博士后研究员、一名研究生和本科生在病毒生态学、微流体学和代谢组学方面得到直接培训。一项教育推广计划将扩大，让中学生参与动手，微生物的高速成像，该项目将在为期三天的研讨会上达到高潮，以推进微流体设备和质谱分析在微生物生态学中的应用。这项研究背后的主要假设是，病毒感染改变了完整的、受感染的浮游植物细胞的化学景观，吸引邻近的趋化细菌和原生浮游动物，并改变了C通量途径。为了验证这一想法，将进行一系列相关的多尺度实验室实验，以1)利用基于微流体的趋化分析来表征不同模型海洋微生物对完整的、受病毒感染的浮游植物释放的溶解有机物（DOM）的反应，2)利用稳定同位素标记、代谢组学分析和趋化分析来确定引发趋化反应的关键病毒衍生的DOM化合物。3)利用与微生物食物网高时空分辨率实时成像相关的升尺度碳动态测量，量化微米尺度的跨营养相遇动力学，并评估其对大规模碳循环的影响。该项目的最终目标是对完整的、病毒感染的细胞在海洋C循环中的作用进行机制理解。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Drifting photosynthetic microbes in surface ocean waters carry out nearly half of global carbon (C) fixation, both supporting the marine food web and reducing atmospheric carbon dioxide (CO2) levels. The fate of C in ocean ecosystems is controlled by myriad individual interactions within a highly interconnected planktonic food web, the sheer complexity of which has hindered predictive understanding of global C cycling. Chemical cues govern microbial interactions, and during infection, marine viruses manipulate the metabolism of phytoplankton and bacteria, facilitating the release of dissolved organic matter from infected cells. This research aims to determine how viral metabolic reprogramming of and organic matter release from intact, infected phytoplankton influences microbial interactions and C cycling. The interdisciplinary, collaborative nature of the project will enable direct training of two postdoctoral researchers, one graduate student, and undergraduate students in viral ecology, microfluidics, and metabolomics. An educational outreach program that engages middle school students in hands-on, high speed imaging of microbes will be expanded, and the project will culminate in a three-day workshop to advance the application of microfluidic devices and mass spectrometry analyses in microbial ecology.The overarching hypothesis behind this research is that viral infection alters the chemical landscape of intact, infected picophytoplankton cells, attracting neighboring chemotactic bacteria and protistan zooplankton, and altering C flux pathways. To test this idea, a series of linked multi-scale laboratory-based experiments will be run to 1) Characterize the response of diverse model marine microbes to dissolved organic matter (DOM) released from intact, virus-infected picophytoplankton using microfluidics-based chemotaxis assays, 2) Identify key viral-derived DOM compounds eliciting chemotactic responses using stable isotope labeling, metabolomics analyses, and chemotaxis assays, and 3) Quantify micron-scale cross-trophic encounter dynamics and evaluate their impact on bulk-scale C cycling using liter-scale measurements of C dynamics linked to high spatiotemporal resolution live imaging of microbial food webs. The ultimate goal of the project is to develop a mechanistic understanding of the role of intact, virus-infected cells in oceanic C cycling.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.