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。抑制竞争对手的化合物的释放被称为化感作用，这一过程被认为对浮游植物很重要，特别是对于那些竞争资源较少但形成密集水华的物种。涉及有毒赤潮甲藻的生态相互作用为理解化学调节的相互作用提供了一个理想的系统。该物种的水华经常发生在墨西哥湾可接近的沿海地区，导致大量鱼类死亡和污染贝类。这些水华的戏剧性后果引发了以下问题。这种有害的藻类在与其他浮游植物的竞争中使用了什么策略？竞争对手经历了哪些致命和亚致命的影响？浮游植物如何对周围环境作出反应、抵抗和解毒？化学线索在这些相互作用中扮演什么角色？化感作用对不同的浮游植物群落有何影响？以前的研究表明，短杆菌对几个自然共存的浮游植物物种具有化感作用，但通常是由短杆菌产生的神经毒性短杆菌毒素以外的化合物起作用。该物种产生不稳定的、500-1000Da的有机化合物的化感作用混合物，导致光系统II活性降低，并扰乱敏感物种的细胞膜，而其他一些竞争对手仍未受到影响。此外，自然开花对与之竞争的硅藻骨骼藻Grethae具有化感作用。反过来，这个物种似乎影响了短杆菌的化学成分，减少了它的化感作用。死亡是短杆菌化感作用的罕见结果；更微妙的非致命性反应占主导地位。总体而言，环境背景可能对预测哪些具有生态重要性的化学介体被释放到海洋系统以及这些化合物对浮游生物群落的后果至关重要。该项目将：1)表征化感作用不同的短杆菌样品中的渗出物代谢组。短链克雷伯氏菌和天然水华样品的渗出物将通过质谱仪(MS)和核磁共振(核磁共振)代谢组学进行研究，以确定参与竞争的候选化学线索。MS蛋白质组学将检测K.brevis蛋白的表达，以测试K.brevis是否上调或下调参与途径网络的关键蛋白以应对竞争对手的挑战。2)以MS代谢组学和蛋白质组学为基础，研究浮游植物对短杆菌化感作用的反应，以期了解化感作用对目标浮游植物的亚致死代谢影响。这项工作将提供一种公正的方法来确定化感作用的分子靶标，并允许测试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)通过比较K.brevis化感作用敏感和抗性竞争对手的代谢组和蛋白质组的变化，将化感敏感性与目标浮游植物的代谢反应联系起来。人们的期望是，与对化感作用最敏感的竞争对手相比，更多的抗性物种经历了解毒途径的增强，以及更强大、更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，因为化感作用在维持近岸水域密集水华方面可能比在近岸水域启动水华方面更重要。更广泛的影响：浮游植物水华可能对当地经济造成毁灭性影响，并对人类健康构成风险。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，最终可能导致预测和控制战略，以减轻这些水华的有害后果。继续努力确定化感作用化合物混合物的特征并确定其对竞争物种的影响，可导致可生物降解的治疗方法，以减少水生和陆地环境中的浮游植物或微生物生长。这项研究建立在过去成功的基础上，应用从化学中学到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的天然产品。该项目将为3名博士生和几名本科生提供培训。博士生将扩大他们在之前的教育培训活动中的角色，参加一个“技术促进教学”计划，将佐治亚理工学院的学生安排在亚特兰大地区的公立高中，其中99%的学生是少数族裔学生。这些非裔美国学生将了解科学的提问性质和美国赤潮的相关问题，以及与人类对海洋环境的影响有关的联系，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.