Collaborative Research: RoL: The rules of life were made to be broken - Connecting physiology, evolutionary ecology, and mathematics to identify a Growth Rate Rule.

所有生物都是由碳(C)、氮(N)和磷(P)等相同的化学元素组成的，尽管这些元素的比例在物种之间存在差异。这种多样性影响了生物在碳固存和养分循环等关键生态系统服务中发挥的作用。然而，科学家们还没有完全了解生物体内碳、氮、磷的比例的生物学规律。一种假设是C:N:P的比例是生物体生长速度的函数，因为为了快速生长，生物体必须产生富含P的结构来推动细胞物质的快速构建。虽然各种数据支持这一观点，但其他研究并不支持这一观点，因此研究人员还不知道这种“增长率规则”何时成立，何时不成立。这个项目将把三种物种（细菌、藻类和甲壳类）置于各种环境和进化条件下，以观察每种生物的C:N:P比例何时遵循这种“生长速率规则”，何时不遵循。研究小组还将建立这些过程的数学模型，以预测当遵循（或不遵循）生长速率规则的生物体相互作用时会发生什么。拟议中的研究将促进对食物网和生态系统如何工作的科学理解，并改进对它们如何应对扰动的预测，包括大气中二氧化碳浓度的增加以及农业和污水中氮和磷污染的输入。此外，为了帮助发展一支受过广泛训练的科学工作队伍，该项目将与当地部落社区合作，让美国土著大学生参与研究。本项目旨在确定三个分类群中生长速率、C:N:P比率和细胞分配到富P核糖体之间是否存在密切耦合的条件：臭假单胞菌（一种异养细菌）、莱茵衣藻（一种光合藻类）和水蚤（一种甲壳类食性动物）。首先，假单胞菌、衣单胞菌和水蚤将在关键不可替代资源（能源、氮、磷）的限制下生长。将量化生长、生物量、排泄和再矿化C:N:P化学计量、细胞RNA和蛋白质含量以及代谢率之间的关系。这些测量结果将用于建立这些细胞过程的数学模型。接下来，项目将完成一系列进化实验，在不同资源的限制下，对假单胞菌、衣单胞菌和水蚤进行选择。产生的后代将在项目的第一个组成部分中进行评估。然后，后代将用于生态实验，以评估进化反应如何影响生态过程。最后，这些实验的结果将用于开发和测试生态和进化动力学的新数学模型。拟议的工作将产生一些资源供科学界使用，包括三种模式生物对生态挑战的生理和转录组反应数据，以及将与同事共享的选定细胞系储存库。该项目将培养具有基因组学、生理学、生态学、进化论和数学等多个学科专业知识的博士后、研究生和本科生。如果成功，该项目将推进我们对生物系统的理解，从基因到生态系统。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。

All organisms are made up of the same set of chemical elements such as carbon (C), nitrogen (N), and phosphorus (P), although there are differences in the proportions of these elements among species. Such diversity affects the roles organisms play in key ecosystem services such as carbon sequestration and nutrient cycling. However, scientists don't yet have a complete understanding of the biological rules that dictate the proportions of C, N, and P in living things. One hypothesis is that C:N:P proportions are a function of how fast an organism grows because, to grow fast, organisms must produce P-rich structures to drive rapid construction of cellular materials. While various data support this view, other studies do not and so researchers do not yet know when this "growth rate rule" holds and when it doesn't. This project will subject three species (a bacterium, an alga, and a crustacean) to a variety of environmental and evolutionary conditions to see when C:N:P proportions of each organism follow this "growth rate rule" and when they don't. The research team will also build mathematical models of these processes to predict what happens when organisms that do (or do not) follow the growth rate rule interact with each other. The proposed research will advance scientific understanding how food webs and ecosystems work and improve predictions of how they respond to perturbations, including increasing atmospheric carbon dioxide concentrations and inputs of nitrogen and phosphorus pollution from agriculture and sewage. Furthermore, to help develop a broadly trained scientific work force, the project will partner with local tribal communities to engage Native American undergraduate students in the research.This project seeks to establish the conditions under which there is or is not a close coupling among growth rate, C:N:P ratios, and cellular allocation to P-rich ribosomes in three taxa: Pseudomonas putida (a heterotrophic bacterium), Chlamydomonas reinhardtii (a photosynthetic alga), and Daphnia pulicaria (a crustacean consumer). First, Pseudomonas, Chlamydomonas, and Daphnia will be grown under limitation by key non-substitutable resources (energy, N, P). Associations among growth, biomass, excretion and remineralization C:N:P stoichiometry, cellular RNA and protein contents, and metabolic rates will be quantified. These measurements will be used to develop mathematical models of these cellular processes. Next, the project will complete a series of evolution experiments, subjecting Pseudomonas, Chlamydomonas, and Daphnia to selection under limitation by different resources. The resulting descendants will be assessed as in the first component of the project. Then, the descendants will be used in ecological experiments to evaluate how evolutionary responses affect ecological processes. Finally, results from these experiments will be used to develop and test new mathematical models of ecological and evolutionary dynamics. The proposed work will produce several resources for use by the scientific community, including data on physiological and transcriptomic responses of three model organisms to ecological challenges as well as a repository of selected lines that will be shared with colleagues. The project will produce uniquely trained postdoctoral researchers, graduate students, and undergraduates with expertise in many disciplines, including genomics, physiology, ecology, evolution, and mathematics. If successful, the project will advance our understanding of biological systems from genes to ecosystems.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.