Collaborative Research: DMS/NIGMS2: Computational and Experimental Analysis of Choanoflagellate Hydrodynamic Performance - Selective Factors in the Evolution of Multicellularity

合作研究：DMS/NIGMS2：领鞭毛虫水动力性能的计算和实验分析 - 多细胞进化中的选择因素

• 批准号: 2054333
• 负责人: Lisa Fauci
• 金额: $ 56.13万
• 依托单位: Tulane University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2021
• 资助国家: 美国
• 起止时间: 2021-07-01 至 2025-06-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2054333&HistoricalAwards=false
• 关键词: Collaborative; Research; DMS; NIGMS2; Computational

The evolution of multicellular animals from a unicellular protozoan ancestor was a pivotal transition in the history of life on earth. Choanoflagellates are protozoans that share a common ancestor with animals. They can be unicellular or form multicellular colonies by cell division, so we are studying them to gain insights about the evolution of multicellularity. For multicellularity to have evolved via natural selection in the ancestors of animals, the performance of activities that affected growth, reproduction, and survival would have been better for colonies than for single cells. This project will focus on performance differences between unicellular and multicellular choanoflagellates of activities that affect their fitness: swimming, feeding, and avoiding predation – all of which depend upon the fluid flow around the organisms. This project also will address an important ecological issue. Choanoflagellates and other microscopic protozoans that eat bacteria and are in turn consumed by small animals are a critical link in aquatic food webs. Many protozoans are unicellular, while others form multicellular colonies, but the consequences to swimming, feeding, and escape performance of being single-celled versus multicellular are not yet understood. Choanoflagellates that produce both unicellular and multicellular forms permit us to study the effects of colony formation on the performance of these functions within a single species. A unicellular choanoflagellate has an ovoid cell body and a single flagellum surrounded by a collar of microvilli. The cell swims by waving its flagellum, which also creates a water current that brings bacteria to the collar of prey-capturing microvilli. We will coordinate laboratory experiments with mathematical models and computer simulations that study the hydrodynamic mechanisms that determine the performance of choanoflagellates. Thus, the principles learned from choanoflagellates about the performance of single cells versus multicellular colonies may shed light on mechanisms affecting ecological interactions of aquatic protozoans, as well as on the evolutionary origins of animals. The project will also provide opportunities for undergraduate and graduate students, and postdoctoral scholars to participate in the research.Feeding success and predator avoidance are examples of performance that might have been important selective factors in the evolution from single cells to multicellularity. Our interdisciplinary team will coordinate laboratory experiments, mathematical modeling, and computational simulations to study the hydrodynamics of swimming, feeding, and interacting with predators by unicellular versus colonial choanoflagellates of various configurations, and of pumping and feeding by sponge choanocytes. Models will be developed that probe the effects of cell morphology, number, and arrangement that can be varied in systematic ways not possible with real choanoflagellates. These microscale systems require novel methods that capture cell morphology, geometry of confining structures, dynamic attachment, and detachment of bacteria from choanoflagellate collars, and the chemical and hydrodynamic signals presented to predators. The method of regularized Stokeslets will be advanced to model these complex systems. Lab experiments will use species of choanoflagellates that can be unicellular and form rosette colonies with flagella pointing outwards, or that form cup-shaped colonies that can turn inside-out so the flagella line the cup, as well as protozoan predators on choanoflagellates. Micro videography will be used for particle-tracking velocimetry of flow fields produced by the choanoflagellates, and to measure swimming speeds, feeding rates, and interactions with predators.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.

多细胞动物从单细胞原生动物祖先的演变是地球生命史上的关键转变。 Choanoflagellates是原生动物，与动物共有共同的祖先。它们可以按细胞分裂形成单细胞或多细胞菌落，因此我们正在研究它们，以了解多细胞性的进化。为了使多细胞通过动物祖先的自然选择进化，影响生长，繁殖和生存的活动的表现对菌落来说比单细胞更好。该项目将重点介绍影响其适应性的活动的单细胞和多细胞choanoferations：游泳，喂养和避免预测 - 所有这些都取决于生物体周围的流体流动。该项目还将解决一个重要的生态问题。食用小动物食用并被小动物食用的choanoflagelates和其他微观原生动物是水生食物网的关键联系。许多原生动物是单细胞的，而其他原生动物则形成多细胞菌落，但是尚不清楚游泳，喂食和逃避性能的后果。产生单细胞和多细胞形式的choanofallages使我们能够研究菌落形成对单个物种中这些功能的性能的影响。单细胞的choanoflagelate具有卵形细胞体和一个被微绒毛项圈包围的单个鞭毛体。该细胞通过挥舞鞭毛游泳，这也会产生一种水流，从而将细菌带到捕食捕获的微绒毛上。我们将与数学模型和计算机模拟协调实验室实验，这些模型和计算机模拟研究确定Choanoflagelates性能的流体动力学机制。这是从choanofepelate中学到的有关单细胞与多细胞菌落的性能的原则可能会阐明影响水生原生动物生态相互作用以及动物的进化起源的机制。该项目还将为大学生和研究生提供机会，并在博士后学者参与研究。进食成功和避免捕食者的示例是表现的示例，这些示例可能是从单个细胞到多细胞性的进化中重要的选择性因素。我们的跨学科团队将协调实验室实验，数学建模和计算模拟，以研究游泳，喂养的流体动力学，并通过各种构型的单细胞与殖民地choanofelates与捕食者相互作用，并研究了赞助者Choanocycytes的泵送和泵送和喂食。将开发模型，以探测细胞形态，数量和排列的影响，而实际choanofelate不可能以系统的方式变化。这些显微镜系统需要新的方法，以捕获细胞形态，狭窄结构的几何形状，动态依恋以及细菌从Choanoflagellate锁领中脱离，以及呈现给捕食者的化学和水动力信号。正规化的stokeslet的方法将提出来对这些复杂系统进行建模。实验室实验将使用可以单细胞的choanofagellates物种，并形成玫瑰花结菌落，鞭毛向外指向，或形成杯状菌落，可以将杯形倒入内而外，以使杯子杯，以及在choanoflagelates上的原生动物捕食者。微观视频将用于Choanoflagelates产生的流场的粒子跟踪速度计，并测量游泳速度，进食速度和与捕食者的相互作用。该奖项反映了NSF的法定任务，并通过使用该基金会的知识分子和更广泛的影响来评估NSF的法定任务，并被视为珍贵的支持。