Collaborative Research: Role of small-sized protists in the microbial loop with emphasis on interactions between mixotrophic protists and picocyanobacteria

合作研究：小型原生生物在微生物循环中的作用，重点是混合营养原生生物和微微蓝藻之间的相互作用

• 批准号: 1458095
• 负责人: Eunsoo Kim
• 金额: $ 8.06万
• 依托单位: American Museum Natural History
• 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: 2015-06-01 至 2019-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1458095&HistoricalAwards=false
• 关键词: Collaborative; Research; Role; small; sized

Protists are mostly single-celled, eukaryotic microorganisms, including algae and protozoans. They are ubiquitous, diverse, and major contributors in oceanic food webs. Determining their taxonomic identity and the extent to which they contribute to carbon and nutrient cycles (whereby carbon and minerals are continuously changed chemically in the environment and reincorporated in living organisms) are among the major goals of this study. Moreover, the investigators will study how they respond to environmental change, one of the most important and challenging current problems in oceanography. Answering these questions is fundamental to understanding how living organisms in the ocean environment interact with one another and contribute to the health and productivity of the ocean. The main goal of the project is to investigate biotic interactions of small-sized protists with very tiny cyanobacteria also known as picocyanobacteria, which represent the most abundant photosynthetic organisms in the ocean. These studies will be done both in ocean environments and in laboratory experimental settings. Considering the limited knowledge on this topic, the work planned in this project promises important and exciting discoveries. Two early career female scientists will lead this project. In addition, one postdoctoral scholar, one graduate student, and at least three undergraduate summer interns will participate in the proposed research activities. The principal investigators will create a strong public outreach program that will engage middle school students in hands-on activities related to ocean sciences, and will produce a video in collaboration with the Education Department at the American Museum of Natural History. The video will summarize the major findings of the proposed research. It can be used in schools and in informal learning settings, including access by the public on the Internet through the Museum's Science Bulletins web page.Single-celled eukaryotic microorganisms or protists, though largely outnumbered by picocyanobacteria (Prochlorococcus and Synechococcus), contribute significantly to ocean carbon biomass and primary productivity, partially by virtue of their larger cell size. In addition, small planktonic protists can regulate picocyanobacteria abundance through grazing. The main goal of this project is to investigate biotic interactions of planktonic pico- and nano-sized eukaryotes with picocyanobacteria, both in the field and in laboratory settings. A set of field- and culture-based experiments will be conducted, using state-of-the-art methodologies, including fluorescence-activated cell sorting, isotope and fluorescent stain labeling, and next-generation molecular sequencing to address the research objectives. Operationally, this project is structured around two objectives: Objective 1 is to assess the contribution of small protists to carbon and nutrient cycling through measurement of primary production, bacterivory, mixotrophy and phosphorus uptake in major microbial groups, and evaluate the role of nutrient availability in controlling mixotrophy. Objective 2 will focus on assessing the distribution and diversity of small-sized protists that feed on picocyanobacteria and further evaluate the role of nutrient availability among the protists that are mixotrophic. To reach these objectives field-based experiments will be conducted in contrasted environments: the North Pacific subtropical gyre (phosphorus replete, dominated by Prochlorococcus at Sta. ALOHA) and the North West Mediterranean sea (phosphorus deplete, dominated by Synechococcus at Sta. DYFAMED). Complementary experiments using model protists and picocyanobacteria will be conducted using controlled cultures in the lab. The work will provide critical new information on the phylogenetic diversity and function of marine microbial eukaryotes, with emphasis on their ecological role as predators (phagotrophy, mixotrophy) on, and competitors with, the picoyanobacteria Prochlorococcus and Synechococcus.

原生生物大多是单细胞真核微生物，包括藻类和原生动物。它们在海洋食物网中无处不在，种类繁多，是主要的贡献者。确定它们的分类身份以及它们对碳和养分循环（碳和矿物质在环境中不断发生化学变化并重新融入生物体）的贡献程度是本研究的主要目标之一。此外，研究人员将研究它们如何应对环境变化，这是海洋学中最重要和最具挑战性的问题之一。探讨这些问题对于了解海洋环境中的生物如何相互作用并促进海洋的健康和生产力至关重要。该项目的主要目标是调查小型原生生物与非常微小的蓝细菌（也称为picocyanobacteria）的生物相互作用，这是海洋中最丰富的光合生物。这些研究将在海洋环境和实验室实验环境中进行。考虑到对这一主题的知识有限，该项目计划的工作有望带来重要和令人兴奋的发现。两位早期职业女性科学家将领导这个项目。此外，一名博士后学者，一名研究生和至少三名本科生暑期实习生将参加拟议的研究活动。主要研究人员将创建一个强大的公共宣传计划，让中学生参与与海洋科学相关的实践活动，并将与美国自然历史博物馆的教育部门合作制作一个视频。该视频将总结拟议研究的主要发现。单细胞真核微生物或原生生物虽然在数量上远不及微蓝细菌（原绿球藻和聚球藻），但对海洋碳生物量和初级生产力的贡献很大，部分原因是它们的细胞体积较大。此外，小型浮游原生生物可以通过放牧调节微蓝细菌的丰度。该项目的主要目标是研究微藻蓝细菌与微皮科和纳米真核生物在野外和实验室环境中的生物相互作用。将进行一系列基于实地和培养的实验，使用最先进的方法，包括荧光激活细胞分选，同位素和荧光染色标记，以及下一代分子测序，以解决研究目标。在操作上，这个项目是围绕两个目标：目标1是通过测量主要微生物群体的初级生产力，噬菌性，兼养性和磷的吸收来评估小型原生生物对碳和营养循环的贡献，并评估营养物质的可用性在控制兼养性中的作用。目标2将侧重于评估的分布和多样性的小型原生生物的饲料picocyanobacteria，并进一步评估的营养物质的可利用性之间的作用，是兼养的原生生物。为了达到这些目标，将在对比环境中进行基于实地的实验：北太平洋亚热带环流（磷充足，在Sta. ALOHA）和西北地中海（磷耗尽，在Sta. DYFAMED）。使用模式原生生物和微蓝细菌的补充实验将在实验室中使用受控培养物进行。这项工作将提供关于海洋微生物真核生物系统发育多样性和功能的重要新信息，重点是它们作为捕食者（吞噬、混合营养）和竞争对手的生态作用，包括微蓝细菌原绿球藻和聚球藻。