MIP: Protist-Prokaryote Symbioses in Bathyal Sulfidic Sediments: Santa Barbara Basin Flagellates and Ciliates

根据显微研究，在圣巴巴拉盆地(SBB)缺乏氧气、富含硫化物的深海沉积物中发现了丰富多样的原生生物群落。这些真核生物中的大多数，其中许多属于科学上新发现的分类群，以一种假定的共生组合形式庇护着原核生物。目前，这些相关原核生物的身份和生理作用/代谢活动尚不清楚。本项目的目标是通过结合基于培养、分子、细胞生物学和地球化学的方法来阐明这些联合的宿主-共生体的身份和功能，从而研究在先前的研究中在SBB中观察到的四个特定的原核生物-真核生物联合(假定的共生体)。这些方法包括rRNA和功能基因的分析，针对rRNA的荧光原位杂交研究(FISH)，分子鉴定和显微放射自显影相结合(MAR-FISH)，以及显微镜分析(扫描电子显微镜、透射电子显微镜)。资料将在两次为期5天的海洋巡航中收集。待分析的特定关联体涉及以下宿主：Calkinsia aureus(鞭毛虫与外生物体)，Euglenid sp.(鞭毛虫与外生物体)，鞭毛虫(具纤毛虫与外生物体)，以及后生盐藻或Parablepharisma sp.(纤毛虫内生或外生)。这些假定的内生和外生共生体被认为具有各种代谢能力。这个项目将大大提高我们对原核生物-真核生物在一个研究较少的海洋栖息地中的相互作用的了解。大多数SBB真核生物，其中许多尚未被描述，与似乎是假定的共生体的原核生物有联系。这些相关原核生物的生理学、系统学和新陈代谢尚不清楚。在这个硫酸盐和微氧/缺氧的深海环境中，阐明微生物群落中原核生物和真核生物之间的共生关系将有助于阐明微生物群落中的共生生物在它们适应这些环境方面所发挥的作用，以及它们对该环境的生物地球化学的潜在影响。此外，共生体是通过引入新的遗传物质进行进化变化的潜在载体，因此代表了物种形成的可能机制。共生也可能允许生态位和栖息地的扩大，这可能是真核生物早期进化和多样化的一个主要因素。该项目将包括本科生和研究生、K-12教师和普通公众的积极参与，以及通过基于互联网的知识网络、广泛发行的专业科学期刊上的出版物、教育活动(例如，为中学教师和研究科学家举办的讲习班)和研讨会广泛传播成果。

On the basis of microscopic studies it is established that an abundant and diverse protistan community occurs in the oxygen-depleted, sulfide-enriched deep-sea sediments of the Santa Barbara Basin (SBB). The majority of these eukaryotes, many of which belong to taxa that are new to science, harbor prokaryotes in a putative symbiotic association. At present, the identity and physiological role/metabolic activities of these associated prokaryotes are unknown. The goal of this project is to investigate four specific prokaryote-eukaryote associations (putative symbioses) that were observed in SBB during previous studies by elucidating the host-symbiont identities and functions of these associations using a combination of culture-based, molecular, cell biological, and geochemical methods. These approaches include analyses of rRNA and functional genes, fluorescent in situ hybridization studies targeting rRNA (FISH), a combination of molecular identification and microautoradiography (MAR-FISH), and microscopical analyses (SEM, TEM). Material will be collected on two 5-day oceanographic cruises. The specific associations to be analyzed involve the following hosts: Calkinsia aureus (flagellate with ectobionts), Euglenoid sp. (flagellate with ectobionts), Metopus verrucosus (ciliate with ectobionts), and Metopus halophila or Parablepharisma sp. (ciliates with endobionts or ectobionts). These putative endo- and ectosymbionts are hypothesized to have a variety of metabolic capabilities. This project will significantly enhance our knowledge of prokaryote-eukaryote associations in a poorly studied marine habitat. The majority of the SBB eukaryotes, many of which are yet to be described, have associations with prokaryotes that appear to be putative symbionts. The physiology, systematics, and metabolism of these associated prokaryotes are unknown. Elucidating the symbiotic relationships between prokaryotes and eukaryotes within the microbial community in this sulfidic and micro-oxic/anoxic deep-sea environment will shed light on the role that symbioses play within microbial consortia in their adaptation to these environments, and their potential impact on the biogeochemistry of that environment. Further, symbioses are potential vehicles for evolutionary change through the introduction of new genetic material, and therefore represent possible mechanisms of speciation. Symbioses may also allow for niche and habitat expansion, possibly a major factor in the early evolution and diversification of eukaryotes. This project will include active involvement of undergraduate and graduate students, K-12 teachers, and the lay public, as well as broad dissemination of results via internet-based knowledge networks, publications in widely-circulated professional scientific journals, educational activities (e.g., workshops for both secondary school teachers and research scientists), and seminars.