Unity and Diversity of Ultrastructural Systems in Single Celled Eukaryotes

30多亿年来，微生物在丰度和多样性方面一直主宰着地球，但微生物的基本和创新特性是所有生物体中最不了解的。在微生物生命的三大谱系（真核生物、细菌和微生物）中，单细胞真核生物是迄今为止最复杂的，具有细胞核、内膜系统、共生获得的细胞器和支持大量细胞延伸和行为的精细细胞骨架。尽管只有一个细胞组成，但每个微生物真核生物本质上都是一个宇宙，我们对这些生物的理解已经推翻了长期以来对细胞多样性的看法。因此，拟议的研究计划旨在探索这个陌生的世界，以帮助解开生命的总组成，相互关系和历史。该研究旨在发现和表征单细胞真核生物中的新型超微结构系统，并为由数字图像和DNA序列组成的全物种生命百科全书做出贡献。 个别项目将跨越真核生物多样性的广泛取样，以解决超微结构性状进化的大规模模式（例如，收敛）。该研究计划将继续并行研究四种主要的单细胞真核生物群，它们可以说是地球上真核生物最不相似的三种模式：捕食、光自养和寄生。海洋捕食性鞭毛虫（如裸藻、甲藻和低温单胞菌）的形态变化具有独立但对应的模式，是研究细胞进化中的限制和重复创新的理想比较系统。所有这三个群体都在沙粒之间的空间中多样化，并独立获得了复杂的进食装置，滑翔运动模式，与细菌的共生关系以及光合细胞器。拟议的研究计划还将解决第四组真核生物，为生命史上最神秘的进化转变之一提供令人信服的见解：专性细胞内寄生虫从自由生活的光自养祖先的起源。顶复门与自由生活的腰鞭毛虫密切相关，尽管作为人类和牲畜的病原体而臭名昭著（例如，疟原虫），大多数顶复门多样性在世界海洋中蓬勃发展。apicomplexans的起源和多样化将通过探索海洋gregarines，这是大的和动态的单细胞寄生虫感染海洋无脊椎动物宿主的比较超微结构和分子生物学来解决。 单细胞真核生物多样性的研究本质上是探索性的，其进展可分为五个阶段：（1）从自然界中发现、分离和培养生物（例如，这些技术包括：（1）利用光学显微镜、荧光共聚焦显微镜和电子显微镜对生物体进行鉴定并确定其超微结构特征;（2）利用光学显微镜、荧光共聚焦显微镜和电子显微镜对生物体进行鉴定并确定其超微结构特征;（3）对生物体进行分子特征鉴定;（4）与图像处理、下一代测序和分子生物遗传学有关的计算分析;（5）利用比较方法进行进化综合。拟议的研究计划将加速从不同环境中发现新的真核细胞谱系，扩大和完善理解真核生物多样性的整体系统发育框架，并确定这些生物体解决基本生物学问题的非常规方法（例如，细胞运动、进食和光感受）。

For over 3 billion years, microbes have dominate the planet in terms of abundance and diversity, yet the fundamental and innovative properties of microbes are the least understood of all organisms. Of the three major lineages of microbial life (Eukarya, Bacteria and Archaea), single-celled eukaryotes are by far the most complex, having nuclei, endomembrane systems, symbiotically acquired organelles and elaborate cytoskeletons supporting a vast array of cell extensions and behaviors. Despite being composed of only a single cell, each microbial eukaryote is essentially a universe in and of itself, and advances in our understanding of these organisms have overturned long-held views about the diversity of cells. Accordingly, the proposed research program is designed to explore this foreign world in order to help unravel the total composition, interrelationships and history of life. The research aims to discover and characterize novel ultrastructural systems in single-celled eukaryotes and make contributions to an all-species Encyclopedia of Life, consisting of digital images and DNA sequences. Individual projects will span a broad sampling of eukaryotic diversity in order to resolve large-scale patterns of ultrastructural trait evolution (e.g., convergence). The research program will continue to study, in parallel, four major groups of single-celled eukaryotes that encompass what are arguably the three most dissimilar modes of eukaryotic life on the planet: predation, photoautotrophy, and parasitism. The independent but corresponding patterns of morphological change in marine predatory flagellates, such as euglenids, dinoflagellates and cryomonads, represent an ideal comparative system for investigating the constraints and reoccurring innovations in cell evolution. All three groups have diversified within the spaces between grains of sand and have independently acquired sophisticated feeding apparatuses, modes of gliding locomotion, symbiotic associations with bacteria, and photosynthetic organelles. The proposed research program will also address a fourth group of eukaryotes that provides compelling insights into one of the most enigmatic evolutionary transformations in the history of life: the origin of obligate intracellular parasites from free-living, photoautotrophic ancestors. Apicomplexans are closely related to free-living dinoflagellates, and despite being infamous as pathogens of humans and livestock (e.g., Plasmodium), most of apicomplexan diversity is thriving in the world’s oceans. The origin and diversification of apicomplexans will be addressed by exploring the comparative ultrastructure and molecular phylogeny of marine gregarines, which are large and dynamic single-celled parasites that infect marine invertebrate hosts. Research on the diversity of single-celled eukaryotes is, in essence, exploratory and progresses in five phases: (1) discovery, isolation and cultivation of the organisms from nature (e.g., Bamfield Marine Sciences Centre and other regions of the Pacific Ocean); (2) identification and ultrastructural characterization of the organisms using light, fluorescence confocal and electron microscopy; (3) molecular characterization of the organisms; (4) computational analyses associated with image processing, next-generation sequencing and molecular phylogenetics; and (5) evolutionary synthesis using comparative methods. The proposed research program will accelerate the discovery of new lineages of eukaryotic cells from diverse environments, expand and refine the overall phylogenetic framework for understanding eukaryotic diversity, and identify unconventional ways in which these organisms have solved basic biological problems (e.g., cell locomotion, feeding, and photoreception).