Collaborative Research: Systems analysis of the interplay between oxygenic photosynthesis and nitrogen fixation in a unicellular cyanobacterium

现代农业严重依赖化肥作为生物可利用氮的来源。化肥的化学合成是能源密集型的，这个过程会产生温室气体，而温室气体是气候变化的主要驱动力。此外，化肥的使用总是会导致与径流有关的问题，对环境有害。一个潜在的解决方案是开发固氮作物。这在生物学上是一个巨大的挑战，因为氧是固氮酶的有力抑制剂，固氮酶是催化固氮的酶。产氧的光合作用生物是生物圈中氧气的主要生产者。其中，一些蓝藻菌株还可以利用光合作用中捕获的能量来固定氮素。这个项目的中心目标是深入了解蓝藻中适应两个拮抗过程--光合作用和固氮--的生物系统。这些努力的成功将揭开发展固氮作物的设计原则，并将对基础生物学和生物技术产生深远影响。项目活动还包括(I)为当地和国际本科生提供培训；(Ii)由华盛顿大学国际能源、环境和可持续发展中心组织的针对科学贫困个人的外展活动。单细胞重氮营养蓝藻是唯一同时存在氧气光合作用和固氮作用的细胞平台。这些微生物已经开发出复杂的策略，通过暂时分离它们，在同一个细胞中执行这些拮抗过程。蓝藻是唯一具有良好特征的生物钟的原核生物，被认为协调这两个过程。然而，对这些生物调节新陈代谢以适应固氮和光合作用的分子机制缺乏详细的了解。该计划是使用最近开发的单细胞重氮菌Cyanothess sp.的遗传修饰系统。51142，从战略上探讨这些问题。在这个项目中，系统生物学方法被用来剖析协调光合作用和固氮的调节层次结构。总体而言，这些研究有助于解开光合作用和固氮在单个细胞中整合的谜团。它们提供了昼夜循环中发生的高度协调的变化的量化地图，告知调节事件如何影响新陈代谢以及新陈代谢产物如何重置调节。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Modern agriculture is critically dependent on fertilizers as the source of biologically available nitrogen. Chemical synthesis of fertilizers is energy intensive, and the process generates greenhouse gases that are a major driver of climate change. Moreover, application of fertilizers invariably leads to run-off related issues that are detrimental to the environment. One potential solution is development of nitrogen-fixing crop plants. This is a grand challenge in biology, since oxygen is a potent inhibitor of nitrogenase, the enzyme that catalyzes nitrogen fixation. Oxygenic photosynthetic organisms are the primary producers of oxygen in the biosphere. Among them, some cyanobacterial strains can also fix nitrogen using the energy captured during photosynthesis. The central objective of this project is to develop a deep understanding of the biological system in cyanobacteria that accommodates the two antagonistic processes, photosynthesis and nitrogen fixation. Success in these efforts will unravel design principles to develop nitrogen-fixing crop plants and will have far reaching implications in basic biology as well as biotechnology. The project activities also include (i) providing training for local and international undergraduate students and (ii) outreach activities for scientifically underprivileged individuals, organized by the International Center for Energy, Environment and Sustainability at Washington University.Unicellular diazotrophic cyanobacteria are the only cellular platforms in which oxygenic photosynthesis and nitrogen fixation coexist. These microbes have developed sophisticated strategies to perform these antagonistic processes in the same cell by temporally separating them. Cyanobacteria are the only prokaryotes with a well characterized circadian clock that is thought to coordinate these two processes. However, a detailed understanding of the molecular mechanisms by which these organisms adjust their metabolism to accommodate both nitrogen fixation and photosynthesis is lacking. The plan is to use a recently developed genetic modification system for the unicellular diazotrophic strain Cyanothece sp. ATCC 51142 to strategically probe these questions. During this project, a systems biology approach is deployed to dissect the regulatory hierarchies that coordinate photosynthesis and nitrogen fixation. Overall, these studies help unlock the puzzle of the integration of photosynthesis and nitrogen fixation in a single cell. They provide a quantitative map of the highly orchestrated changes occurring during the day-night diel cycle informing how regulatory events affect metabolism as well as how the products of metabolism reset regulation.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.