Collaborative Research: The Role of Iron-oxidizing Bacteria in the Sedimentary Iron Cycle: Ecological, Physiological and Biogeochemical Implications

合作研究：铁氧化细菌在沉积铁循环中的作用：生态、生理和生物地球化学意义

• 批准号: 1459600
• 负责人: David Emerson
• 金额: $ 52.25万
• 依托单位: Bigelow Laboratory for Ocean Sciences
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-03-01 至 2018-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1459600&HistoricalAwards=false
• 关键词: Collaborative; Research; Role; Iron; oxidizing

Iron is one of the most abundant elements on Earth and is an essential element for life. Despite its abundance, iron is not always biologically available. For example, in the water column of the ocean, iron is easily oxidized and precipitates or sinks to the sediments. This can result in there being such a deficit of iron in the open ocean that it is often the primary limiting nutrient for the growth of phytoplankton that form the base of the marine food web. Marine sediments can be a major source of iron to the ocean, when it is made biologically available. Interestingly, one group of bacteria, the iron-oxidizing bacteria (FeOB), can use iron directly as an energy source to fuel their growth, and may govern the availability of iron to other parts of the ocean. While this group can be abundant at hydrothermal vents, little is known about their abundance or activity in marine sediments. Are these bacteria playing an important role in controlling the flux of iron from the sediments to the water column? To answer this, sediments on the east and west coasts of the United States will be analyzed to characterize and quantitate the diversity and abundance of FeOB. In addition, a series of laboratory experiments will be aimed at understanding the specific role they play in controlling iron flux from the sediments to the ocean, as well as the technically challenging question of determining the lower limit of oxygen at which they can grow. This work has relevance to our understanding of how biological control of a seemingly minor constituent in seawater, iron, could have implications for productivity of the entire ocean. Notably, a predicted impact of climate change on marine environments is to decrease oxygen levels in the ocean. This could have a profound influence on the sedimentary iron cycle, and possibly lead to greater inputs of iron, which could in turn alleviate iron-limitation in some regions of the ocean, thereby enhancing the rate of CO2-fixation and draw down of CO2 from the atmosphere. This project will provide training for a postdoctoral scientist, graduate students and undergraduates. Public outreach will include a student initiated exhibit, entitled "Iron and the evolution of life on Earth" at the Harvard Museum of Natural History providing a unique opportunity for undergraduate training and outreach. The central hypothesis of this proposal is that FeOB are more common in marine sedimentary environments than previously recognized, and play a substantive role in governing the iron flux from the sediments into the water column by constraining the release of dissolved iron (dFe) from sediments. A survey of near shore regions in the Gulf of Maine, and a transect along the Monterey Canyon off the coast of California will obtain cores of sedimentary muds and look at the vertical distribution of FeOB and putative Fe-reducing bacteria using sensitive techniques to detect their presence and relative abundance. Sediments will be used in a novel reactor system that will allow for precise control of O2 levels and iron concentration to measure the dynamics of the iron cycle under different oxygen regimens. Pure cultures of FeOB with different O2 affinities will be tested in a bioreactor coupled to a highly sensitive mass spectrometer to determine the lower limits of O2 utilization for different FeOB growing on iron, thus providing mechanistic insight into their activity and distribution in low oxygen environments.

铁是地球上最丰富的元素之一，是生命的重要元素。尽管它丰富，但并不总是在生物学上获得铁。 例如，在海洋的水柱中，铁很容易被氧化，沉淀或沉积物沉积到沉积物中。这可能会导致在开阔的海洋中存在如此之多的铁缺乏，以至于它通常是构成海洋食品网络基础的浮游植物生长的主要限制营养素。当生物学上可用时，海洋沉积物可能是海洋铁的主要来源。有趣的是，一组细菌，即铁氧化细菌（FEOB），可以直接用铁作为能源来促进其生长，并可以控制铁对海洋其他部位的可用性。尽管这群在热液通风口可能很丰富，但对海洋沉积物中的丰度或活性知之甚少。这些细菌在控制从沉积物到水柱的铁的通量中起重要作用？为了回答这一点，将分析美国东海岸和西海岸的沉积物，以表征和量化FEOB的多样性和丰度。此外，一系列实验室实验将旨在了解他们在控制从沉积物到海洋的铁通量中所起的特定作用，以及确定它们可以生长的氧气下限的技术挑战性问题。这项工作与我们对海水中看似较小的成分的生物控制如何对整个海洋的生产力产生影响有关。 值得注意的是，气候变化对海洋环境的影响是降低海洋中的氧气水平。这可能会对沉积铁循环产生深远的影响，并可能导致更多的铁投入，进而减轻海洋某些地区的铁限制，从而提高二氧化碳固定速率并从中降低CO2气氛。该项目将为博士后科学家，研究生和本科生提供培训。公众推广将包括一个学生发起的展览，标题为“铁与地球上的生命进化”，这为自然历史博物馆提供了一个独特的本科培训和外展活动的机会。该提议的中心假设是，在海洋沉积环境中，FEOB比以前认识到的更为普遍，并且通过约束从沉积物中溶解铁（DFE）释放，在管理从沉积物进入水柱的铁通量中发挥了实质性作用。对缅因州海湾近岸地区的调查，以及沿着加利福尼亚海岸蒙特雷峡谷的横断面将获得沉积泥浆，并使用敏感技术来检测FEOB的垂直分布和推定的减少FE的细菌存在和相对丰度。沉积物将用于新的反应器系统中，该系统将允许精确控制O2水平和铁浓度，以测量不同氧气方案下铁循环的动力学。具有不同O2亲和力的FEOB的纯培养物将在与高度敏感的质谱仪相连的生物反应器中进行测试，以确定O2利用的下限，以在铁上生长的不同FEOB，从而为其在低氧环境中的活性和分布提供机械洞察力。