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.

从单细胞原生动物祖先进化出多细胞动物是地球生命史上的一个关键转变。 领鞭毛虫是与动物有共同祖先的原生动物。 它们可以是单细胞的，也可以通过细胞分裂形成多细胞集落，因此我们正在研究它们，以深入了解多细胞的进化。 对于动物祖先通过自然选择进化出的多细胞生物来说，影响生长、繁殖和生存的活动的表现对于群体来说会比单细胞更好。 该项目将重点研究单细胞和多细胞领鞭毛虫在影响其健康的活动中的性能差异：游泳、进食和避免捕食——所有这些都取决于生物体周围的液体流动。 该项目还将解决一个重要的生态问题。 鞭毛虫和其他以细菌为食并反过来被小动物吃掉的微小原生动物是水生食物网中的关键环节。 许多原生动物是单细胞的，而另一些则形成多细胞菌落，但单细胞与多细胞对游泳、进食和逃逸性能的影响尚不清楚。产生单细胞和多细胞形式的领鞭毛虫使我们能够研究菌落形成对单个物种内这些功能的表现的影响。 单细胞领鞭毛虫具有卵形细胞体和被微绒毛环包围的单个鞭毛。细胞通过挥动鞭毛来游泳，这也会产生水流，将细菌带到捕获猎物的微绒毛的衣领处。我们将协调实验室实验与数学模型和计算机模拟，研究决定领鞭毛虫性能的流体动力学机制。 因此，从领鞭毛虫中学到的关于单细胞与多细胞菌落性能的原理可能有助于揭示影响水生原生动物生态相互作用的机制，以及动物的进化起源。该项目还将为本科生、研究生以及博士后学者提供参与该研究的机会。成功进食和躲避捕食者的表现可能是从单细胞向多细胞进化过程中重要的选择因素。 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，以研究各种配置的单细胞与群体领鞭毛虫游泳、进食和与捕食者相互作用的流体动力学，以及海绵领毛细胞的泵送和进食。将开发模型来探测细胞形态、数量和排列的影响，这些细胞形态、数量和排列可以以系统的方式变化，而这对于真正的领鞭毛虫来说是不可能的。这些微型系统需要新的方法来捕获细胞形态、限制结构的几何形状、细菌从领鞭毛领上的动态附着和分离，以及向捕食者呈现的化学和流体动力学信号。将改进正则化 Stokeslet 方法来对这些复杂系统进行建模。实验室实验将使用单细胞的领鞭毛虫物种，这些鞭毛虫可以形成鞭毛朝外的玫瑰花状菌落，或者形成可以从内向外翻转的杯形菌落，使鞭毛排列在杯中，以及领鞭毛虫上的原生动物捕食者。微摄像技术将用于对领鞭毛虫产生的流场进行粒子跟踪测速，并测量游泳速度、进食率以及与捕食者的相互作用。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。