Exploring the Linkages Between Trichodesmium spp. Physiology, Diversity and Iron Geochemistry in the Ocean

探索 Trichodesmium spp 之间的联系。

• 批准号: 0623499
• 负责人: Eric Webb
• 金额: $ 66.03万
• 依托单位: University of Southern California
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2006
• 资助国家: 美国
• 起止时间: 2006-10-01 至 2009-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0623499&HistoricalAwards=false
• 关键词: Exploring; Linkages; Between; Trichodesmium; spp.

ABSTRACTProposal No.: OCE-0623499Rates of nitrogen fixation by the colonial cyanobacteria, Trichodesmium spp., long considered the dominant diazotroph in the ocean, can be limited by iron and/or phosphorus. Although models have defined regions within the oceans where diazotrophs, especially Trichodesmium, are predicted to be limited by Fe, light, P or none of these factors, the boundaries of these regions are uncertain. Empirical validation of the models requires field surveys that are difficult to conduct without a rapid diagnostic for Fe or P limitation. Two PIs from the University of Southern California have identified several diagnostic genes for Fe and P limitation that are useful for quickly assessing the Fe and P status with natural Trichodesmium populations in space and time. These genes can also provide insights into the mechanism of Fe uptake. For instance, one of the Fe stress-induced genes is feoB which is predicted to be required for efficient uptake of Fe(II). Although common in facultatively anaerobic bacteria, its presence in open-ocean cyanobacteria is limited to Trichodesmium and another diazotroph, Crocosphaera. The PIs hypothesize that because diazotrophs have a higher Fe requirement due to N2 fixation than other cyanobacteria, they may utilize feoB, perhaps in conjunction with an exogenous or endogenous reductase mechanism, to access additional reservoirs of Fe within the dissolved Fe pool in seawater.The PIs will study the expression of Fe and P diagnostic probes within the western Pacific warm pool to determine if Trichodesmium is Fe or P limited in this region. On an already funded cruise from New Zealand to Hawaii in 2007, they anticipate encountering significant Fe gradients along N-S and E-W transects that span the range over which Trichodesmium becomes Fe-limited. Measurements of Fe and Fe-speciation will be made, including application of novel methods to extend current detection limits for Fe speciation to sub-nanomolar levels. Temporal aspects of the relationship between Fe speciation parameters and the Fe stress diagnostics will also be studied by following the characteristic Trichodesmium abundance maximum at the Hawaii Ocean Time Series Station (HOT) that occurs in the late summer.One component of the Broader Impacts of this proposal is the validation of current global ocean model predictions. This project will also develop a large dataset of Fe concentration measurements in an important, yet understudied regime of the ocean. Furthermore, this project will fund the research for two graduate students and include the participation of undergraduates from small, 4-year colleges on cruises.

摘要提案编号： OCE-0623499菌落蓝细菌，束毛藻属，长期以来被认为是海洋中占主导地位的固氮生物，可能会受到铁和/或磷的限制。虽然模型已经确定了海洋中的固氮生物，特别是束毛藻，被预测为限制铁，光，磷或没有这些因素，这些地区的边界是不确定的。 经验验证的模型需要实地调查，很难进行没有快速诊断铁或磷的限制。来自南加州大学的两名PI已经鉴定了几个用于Fe和P限制的诊断基因，这些基因可用于快速评估天然束毛藻种群在空间和时间上的Fe和P状况。 这些基因也可以提供铁吸收机制的见解。例如，Fe胁迫诱导的基因之一是feoB，预计其是有效吸收Fe（II）所需的。虽然常见于兼性厌氧细菌，但其存在于开放海洋蓝细菌中仅限于束毛藻和另一种固氮生物Crocosphaera。PI假设，由于固氮生物由于N2固定而具有比其他蓝细菌更高的Fe需求，因此它们可能利用feoB，可能与外源或内源还原酶机制结合，研究员将研究Fe和P诊断探针在西太平洋暖池中的表达，以确定束毛藻是否受Fe或P限制在这个地区。 在2007年从新西兰到夏威夷的一次已经资助的巡航中，他们预计会遇到显著的铁梯度，沿着沿着N-S和E-W横断面，跨越Trichodesmium成为铁限制的范围。将对Fe和Fe形态进行测量，包括应用新方法将当前Fe形态的检测限扩展到亚纳摩尔水平。Fe形态参数和Fe应力诊断之间的关系的时间方面也将研究以下特征Trichodesmium丰度最大值在夏威夷海洋时间序列站（HOT），发生在夏末。这一建议的更广泛的影响的一个组成部分是目前的全球海洋模型预测的验证。该项目还将在一个重要但研究不足的海洋区域开发一个大型铁浓度测量数据集。此外，该项目将资助两名研究生的研究，并包括来自小型四年制大学的本科生参加游轮。