EAGER: Cyanobacteria-Bacteria Associations in the Ocean and Their Biogeochemical Consequences

知识价值：远洋海洋细菌和古细菌（“细菌”）在海洋浮游植物固定碳的生物地球化学命运的变化中起主要作用。因此，细菌与初级生产者的耦合对气候和生态系统模型具有影响。由于细菌与有机物质（包括浮游植物细胞）的相互作用是在纳米到微米的尺度上进行的，因此了解细菌与初级生产者的生物地球化学耦合需要了解微米尺度上相互作用的性质和强度。利用原子力显微镜（AFM）， PI最近发现了相当一部分异养（非光合作用）细菌，包括以前被认为是自由生活的聚球菌的自然组合，与其他细菌一起出现。在初步实验中，远洋细菌也与原绿球藻的培养有关（我们还不知道原绿球藻的自然组合是否含有联合细菌）。鉴于聚藻球菌和原绿球藻作为海洋中主要的初级生产者的生物地球化学重要性，它们与异养细菌的共生可能会产生深远的影响。这项EAGER研究有可能改变人们对微生物碳循环和海洋生态系统功能的看法。它可能揭示一个新的微空间背景，例如碳和营养循环的“热点”，特别是在聚藻球菌和原绿球藻是主要主要生产者的低营养水域。这种具有潜在变革性但风险很高的研究非常适合EAGER资助模式。尖端的方法，包括低温电子断层扫描，纳米sims和单细胞系统发育将通过多学科合作来测试关于共生的超微结构和生态系统功能的假设。联合伙伴的系统发育特性将通过对海水样品进行直接显微操作以挑选单个联合细胞，然后进行MDA （Multiple Displacement Amplification）分析来确定。细胞间元素交换的NanoSIMS分析将表征共生的性质和生物地球化学意义。实地研究将检查与相关环境因素有关的共生分布。成功实现PI所详述的目标将产生对共生机制的理解和生物地球化学意义。我们将在一份发行量广泛的杂志上以及通过在适当的会议上的谈话迅速传达我们的发现。更广泛的影响：该研究项目旨在深入了解微生物在海洋生态系统功能、生物碳循环和海洋在全球气候变化中的作用的基本机制。因此，结果也应该与紧迫的社会问题渔业和气候变化有关。公共政策研究所的实验室积极参与从本地到国际的公众教育，拟议的研究结果将以适当的形式广泛传播给公众。本研究将培养1名博士后和1名研究生。

Azam EAGER 1036613Intellectual Merit: Pelagic marine bacteria and Archaea ("bacteria") play major roles in the variability in the biogeochemical fate of carbon fixed by phytoplankton in the ocean. The coupling of bacteria with the primary producers therefore has implications for climate and ecosystem models. Since bacteria interact with organic matter, including phytoplankton cells, at the nanometer to micrometer scale, understanding the biogeochemical coupling of bacteria with primary producers requires knowledge of the nature and strength of interactions at the micrometer scale. Using Atomic Force Microscopy (AFM) the PI recently discovered that a substantial fraction of heterotrophic (non-photosynthetic) bacteria, including the natural assemblages of Synechococcus, previously considered free-living, appeared conjoint with other bacteria. In a preliminary experiment, pelagic bacteria also became associated with cultures of Prochlorococcus (we do not yet know whether natural assemblages of Prochlorococcus harbor conjoint bacteria). In view of the biogeochemical importance of Synechococcus and Prochlorococcus as major primary producers in the ocean, their symbioses with heterotrophic bacteria could have far-reaching consequences.This EAGER study has the potential to change ideas on microbial carbon cycling and marine ecosystems functioning. It may reveal a novel microspatial context, e.g., carbon and nutrient cycling 'hot spots', particularly in oligotrophic waters where Synechococcus and Prochlorococcus are major primary producers. This potentially transformative, but high risk research, is an excellent fit to the EAGER model for funding. Cutting edge methodologies, including cryo-electron tomography, nanoSIMS and single cell phylogenetics will be used through multidisciplinary collaborations to test hypotheses on the ultrastructure and ecosystem function of the symbioses. The phylogenetic identity of the conjoint partners will be determined by direct micromanipulation of seawater samples to pick individual conjoint cells followed by analysis by MDA (Multiple Displacement Amplification). NanoSIMS analysis of intercellular elemental exchanges will characterize the nature and biogeochemical significance of the symbioses. Field studies will examine the distribution of the symbioses in relation to relevant environmental factors. Success in the goals detailed by the PI should yield mechanistic understanding and biogeochemical significance of the symbioses. We will rapidly communicate our findings in a wide circulation journal as well as through talks at appropriate conferences.Broader Impacts: This research project is aimed at gaining insights on fundamental mechanisms underlying the roles of microbes in the functioning of marine ecosystems, biological carbon cycling and the ocean's role in global climate variability. Therefore, the result should also be relevant to pressing societal issues fisheries and climate change. The PI's lab is actively involved in public education from local to international levels, and the findings of the proposed research will be disseminated broadly to the public in appropriately accessible formats. One postdoctoral fellow and one graduate student will receive training during this research.