CAREER: Microbial Activity and Chemoautotrophy in the Deep Sea: Who, How, and How Much?

职业：深海微生物活动和化能自养：谁、如何以及多少？

• 批准号: 2143035
• 负责人: Anne Dekas
• 金额: $ 81.24万
• 依托单位: Stanford University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-04-01 至 2027-03-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2143035&HistoricalAwards=false
• 关键词: CAREER; Microbial; Activity; Chemoautotrophy; Deep

The deep sea, defined as deeper than 200 m, is the largest and least explored habitat on the surface of our planet. It covers nearly two-thirds of the Earth's surface, contains approximately 75% of marine water by volume, and is home to about 55% of all marine microorganisms. Deep-sea microorganisms can play important roles in shaping global chemistry and climate, for example producing and consuming greenhouse gases (e.g., carbon dioxide and nitrous oxide). However, the microbiology of deep-sea waters is understudied relative to that of the surface ocean. Recent data suggests a much more diverse and active microbial community at depth than previously thought, but much remains to be known. For instance, recent estimates suggest that approximately 60% of the microbial species in the deep sea are novel. This project investigates the metabolic activity of deep-sea microorganisms, focusing on chemoautotrophy and the carbon cycle. Chemoautotrophy is a microbial metabolism in which inorganic carbon (e.g., carbon dioxide) is converted to sugar and biomass using chemical energy. This project uses several state-of-the-art sampling and analyses techniques to determine which species conduct chemoautotrophy (who?), what types of chemical energy support it (how?), and at what rate it occurs (how much?) throughout the deep sea. Answering these questions provides insight into deep-sea microbial ecology and quantitative data on the sources and sinks of carbon in deep waters. Results will advance our understanding of the ability of our oceans to sequester carbon over long timescales. This work benefits society through the implications of its findings for our ability to predict and mitigate climate change, as well as its educational mission, which includes training diverse high school, undergraduate, and graduate students in interdisciplinary, climate-relevant science through one-on-one mentorship, hands-on coursework, and the initiation of an annual regional symposium featuring student research. This project investigates uncultured microorganisms' genetic potential and activity in the mesopelagic and bathypelagic oceanographic layers (200 to 4000 m water depth) to characterize deep-sea microbiology and address a discrepancy in the marine carbon cycle, namely, that respiration rates consistently exceed estimates of vertical inputs of carbon to the dark ocean. Chemoautotrophy may explain at least part of this discrepancy, but known types of chemoautotrophy (e.g., coupled to ammonia and nitrite oxidation) are insufficient to bridge the gap, suggesting novel chemoautotrophs and diverse coupled catabolisms. The overarching hypotheses are that (1) deep-sea microorganisms are more active than currently appreciated, (2) the organic carbon required to support this activity is provided, at least in part, by higher rates of endogenous inorganic carbon fixation, and (3) carbon fixation is performed by more phylogenetically and metabolically diverse chemoautotrophs/mixotrophs than currently known. This study uses high-pressure sampling containers during two deep-sea oceanographic expeditions, metagenomics, metatranscriptomics, and stable-isotope experiments coupled to single-cell isotope analyses via nanoSIMS to (1) quantify microbial anabolic activity in general and chemoautotrophy, mixotrophy, and heterotrophy specifically at bulk and single-cell levels, (2) characterize the diversity and distribution of genes and transcripts involved in chemoautotrophy and heterotrophy, (3) identify novel chemoautotrophs and mixotrophs and quantify their contribution to carbon cycling, and (4) investigate the ability of a major chemoautotrophic deep-sea lineage, the Marine Group I Thaumarchaeota, to utilize organic matter. The results have the potential to reveal novel functions in uncultured microbes and change our understanding of marine carbon cycling.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.

深海的定义是深度超过200米，是地球表面最大和最少探索的栖息地。它覆盖了近三分之二的地球表面，包含约75%的海水体积，是约55%的海洋微生物的家园。深海微生物可以在塑造全球化学和气候方面发挥重要作用，例如产生和消耗温室气体（例如，二氧化碳和一氧化二氮）。然而，深海沃茨的微生物学相对于海洋表面的微生物学研究不足。最近的数据表明，深海微生物群落比以前认为的更加多样和活跃，但仍有很多东西有待了解。例如，最近的估计表明，深海中大约60%的微生物物种是新的。该项目研究深海微生物的代谢活动，重点是化能自养和碳循环。化能自养是一种微生物代谢，其中无机碳（例如，二氧化碳）使用化学能转化为糖和生物质。该项目使用几种最先进的采样和分析技术来确定哪些物种进行化能自养（谁？），什么类型的化学能支持它（如何？），以及它发生的速率（多少？）在整个深海。研究这些问题有助于深入了解深海微生物生态学，并提供关于深海沃茨碳源和碳汇的定量数据。研究结果将促进我们对海洋长期固碳能力的理解。这项工作通过其研究结果对我们预测和缓解气候变化的能力的影响以及其教育使命，其中包括培训不同的高中，本科和研究生跨学科，气候相关的科学通过一对一的指导，动手课程，以及启动年度区域研讨会，以学生研究为特色。 该项目调查未培养微生物在中层和深层海洋层（200至4 000米水深）的遗传潜力和活动，以确定深海微生物学的特征，并解决海洋碳循环中的一个差异，即呼吸率一直超过对暗海洋垂直碳输入的估计。化能自养可以解释这种差异的至少一部分，但已知类型的化能自养（例如，偶联氨和亚硝酸盐氧化）不足以弥合差距，提示新的化能自养生物和多样的偶联分解代谢。总体假设是：（1）深海微生物比目前认识到的更活跃，（2）支持这一活动所需的有机碳至少部分是由更高的内源无机碳固定率提供的，（3）碳固定是由比目前已知的在遗传和代谢方面更多样化的化能自养生物/兼养生物进行的。本研究在两次深海海洋学考察、宏基因组学、元转录组学和稳定同位素实验期间使用高压采样容器，通过nanoSIMS结合单细胞同位素分析，以（1）在总体和化学自养、混合营养和异养水平上量化微生物的合成代谢活性，（2）表征参与化能自养和异养的基因和转录物的多样性和分布，（3）鉴定新的化能自养生物和兼养生物并量化它们对碳循环的贡献，和（4）调查一个主要的化能自养深海谱系-海洋第一组Thaumarchaeota-利用有机物质的能力。该研究结果有可能揭示未培养微生物的新功能，并改变我们对海洋碳循环的理解。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。