Waterborne chemical cues in the plankton: a systems biology approach

智力优势：竞争是构建群落的主要力量，包括海洋浮游生物。释放抑制竞争对手的化合物，这一过程被称为化感作用，在浮游植物中被认为是重要的，特别是对那些竞争资源激烈但形成密集繁殖的物种。涉及有毒赤潮鞭毛藻短Karenia的生态相互作用为理解化学介导的相互作用提供了一个理想的系统。该物种的大量繁殖经常发生在墨西哥湾可到达的沿海地区，造成大量鱼类死亡并污染贝类。这些开花的戏剧性后果引发了以下问题。这种有害藻类在与其他浮游植物竞争时采用什么策略？竞争对手会经历哪些致命和亚致命的影响？浮游植物是如何对周围环境做出反应、抵抗和解毒的？化学线索在这些相互作用中扮演什么角色？化感作用如何影响不同的浮游植物群落？先前的研究表明，短链镰刀菌对几种天然共存的浮游植物具有化感作用，但短链镰刀菌产生的神经毒性短链镰刀菌毒素以外的化合物通常是负责的。该物种产生不稳定的500-1000 Da有机化合物的化感作用混合物，导致光系统II活性降低并破坏敏感物种的细胞膜，而其他一些竞争对手则不受影响。此外，短叶藻的自然开花对竞争的大骨藻具有化感作用。这个物种，反过来，似乎影响短链镰刀的化学，减少其化感作用。死亡是一种罕见的结果短叶氏K.化感作用；更微妙的、非致命的反应占据了主导地位。总的来说，环境背景可能是预测哪些生态上重要的化学介质被释放到海洋系统以及这些化合物对浮游生物群落的影响的关键。该项目将：1)表征不同化感作用力的短链镰刀菌样品的分泌物代谢组。我们将利用质谱（MS）和核磁共振（NMR）代谢组学技术对短链乳杆菌菌株和天然华花样品的分泌物进行研究，以确定参与竞争的候选化学线索。短克雷氏菌的蛋白表达将通过MS蛋白质组学来检测短克雷氏菌是否上调或下调参与通路网络的关键蛋白，以应对竞争对手的挑战。2)通过MS-based代谢组学和蛋白质组学研究浮游植物对短叶藻化感作用的反应，寻求了解化感作用对目标浮游植物的亚致死代谢影响。这项工作将为确定化感作用的分子靶点提供一种公正的方法，并允许测试对化感作用的亚致死反应是否包括抑制基本细胞功能和上调与应激和解毒相关的途径。3)将化感敏感性与目标浮游植物的代谢反应联系起来，通过比较对短叶镰刀化感敏感和抗性竞争对手的代谢组学和蛋白质组学变化。我们的期望是，相对于对化感作用最敏感的竞争对手，更具抗性的物种经历了解毒途径的增强和更强大、不受影响的细胞功能。4)确定河口和近海浮游植物对化感作用的生理反应有何不同，因为化感作用对于维持近岸水域的密集华花可能比在近海华花的开始更重要。更广泛的影响：浮游植物大量繁殖会对当地经济造成毁灭性影响，并对人类健康构成威胁。在海洋浮游生物中发现新的化学介导的相互作用和代谢反应可能最终导致预测和控制策略，以减轻这些水华的有害后果。继续努力确定化感化合物混合物的特征并确定其对竞争物种的影响，可能导致生物可降解处理，以减少水生和陆地环境中的浮游植物或微生物的生长。这项研究建立在过去成功的基础上，应用从化学中获得的关于生态过程的经验教训，并利用生态学的见解来发现具有重要生物功能的独特天然产物。本项目将培养3名博士生和数名本科生。博士研究生将扩大他们在以前的教育培训活动中的作用，参加“技术教学”计划，该计划将佐治亚理工学院的学生安置在亚特兰大地区的公立高中，其中约99%的学生是少数民族学生。这些非裔美国学生将学习科学的提问性质和围绕美国赤潮的问题，以及与人类对海洋环境影响的相关联系，通过将科学与他们的日常生活联系起来，激发他们对科学的兴趣。

Intellectual merit: Competition is a major force structuring communities, including the marine plankton. The release of compounds that inhibit competitors, a process known as allelopathy, is hypothesized to be important among phytoplankton, especially for species that compete poorly for resources yet form dense blooms. Ecological interactions involving the toxic red tide dinoflagellate Karenia brevis present an ideal system for understanding chemically mediated interactions. Blooms of this species occur frequently in accessible coastal areas of the Gulf of Mexico, causing massive fish kills and contaminating shellfish. The dramatic consequences of these blooms motivate the following questions. What strategies does this harmful alga use in competition with other phytoplankton? What lethal and sub-lethal effects are experienced by competitors? How do phytoplankton respond, resist, and detoxify their surroundings? What roles do chemical cues play in these interactions? How are different phytoplankton communities affected by allelopathy? Previous studies have shown that K. brevis is allelopathic to several naturally co-occurring phytoplankton species, but compounds other than the known neurotoxic brevetoxins produced by K. brevis generally were responsible. This species produces allelopathic mixtures of unstable, 500-1000 Da organic compounds which cause reduced photosystem II activity and disrupt cell membranes of sensitive species, whereas some other competitors remain unaffected. Moreover, natural blooms of K. brevis were allelopathic to the competing diatom Skeletonema grethae. This species, in turn, appeared to influence the chemistry of K. brevis, reducing its allelopathic effects. Death is a rare outcome of K. brevis allelopathy; more subtle, non-lethal responses have predominated. Overall, environmental context may be critical for predicting what ecologically important chemical mediators are released into marine systems and the consequences of these compounds to plankton communities. The project will: 1) Characterize the exudate metabolome among K. brevis samples of varying allelopathic potency. Exudates of K. brevis strains and natural bloom samples will be studied by mass spectrometry (MS) and nuclear magnetic resonance (NMR) metabolomics to pinpoint candidate chemical cues involved in competition. Karenia brevis protein expression will be examined by MS proteomics to test whether K. brevis up- or down-regulates key proteins involved in pathway networks in response to challenges by competitors. 2) Seek to understand sub-lethal metabolic impacts of exposure to allelopathy on target phytoplankton, by studying responses of phytoplankton to K. brevis allelopathy by MS-based metabolomics and proteomics. This work will provide an unbiased approach to determining molecular targets of allelopathy and allow testing of whether sub-lethal responses to allelopathy include suppressed fundamental cellular functioning and up-regulated pathways related to stress and detoxification. 3) Relate allelopathic sensitivity to metabolic responses in target phytoplankton, by comparing metabolomic and proteomic changes of sensitive versus resistant competitors to K. brevis allelopathy. The expectation is that more resistant species experience enhancement of detoxification pathways and more robust, unaffected cellular function relative to competitors most sensitive to allelopathy. 4) Determine how estuarine and off-shore phytoplankton differ in their physiological responses to allelopathy, because allelopathy may be more important for maintaining dense blooms in near-shore waters than in the initiation of blooms off-shore. Broader impacts: Phytoplankton blooms can be devastating to local economies and pose human health risks. The discovery of new chemically mediated interactions and metabolic responses in the marine plankton could eventually lead to prediction and control strategies to alleviate the harmful consequences of these blooms. Continued effort to characterize mixtures of allelopathic compounds and determine their effects on competing species could lead to biodegradable treatments for reducing phytoplankton or microbial growth in aquatic and terrestrial environments. This study builds on past successes, applying lessons learned from chemistry about ecological processes and using ecological insights to discover unique natural products with important biological functions. This project will provide training for 3 PhD students and several undergraduates. The PhD students will expand their roles in previous educational training activities, participating in a "Tech for Teaching" program that places Georgia Tech students in Atlanta-area public high schools with ~99% minority students. These African-American students will learn about the question-asking nature of science and issues surrounding red tides in the U.S., as well as associated connections to human impacts on marine environments, exciting them about science by connecting it with their daily lives.