How do eukaryotic CO2 fixers co-exist with faster growing prokaryotic CO2 fixers in the oligotrophic ocean covering 40% of Earth?

%20%20真核%20CO2%20固定者%20如何与%20更快%20生长%20原核%20CO2%20固定者%20共存%20%20%20寡营养%20海洋%20覆盖%2040%%20%20地球？

• 批准号: NE/M015831/1
• 负责人: Peter Foster
• 金额: $ 17.22万
• 依托单位: Natural History Museum
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2015
• 资助国家: 英国
• 起止时间: 2015 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FM015831%2F1
• 关键词: How; do; eukaryotic; CO2; fixers

The principal aim of the proposal is to explain the ecological basis of the most extensive biome on Earth - co-existence of eukaryotic CO2 fixers with faster growing prokaryotic CO2 fixers in the open oligotrophic ocean. Eukaryotes dominate CO2 fixation in most of Earth's biomes, e.g. terrestrial, freshwater and some marine (coastal and polar waters), with one but major exception: the oligotrophic oceanic gyres, covering 40% of Earth. Why have energetically superior eukaryotes been unable to outgrow prokaryotes despite millions of years of co-evolution in the gyres?We hypothesise that co-existence of CO2 fixing eukaryotes and prokaryotes is sustained by episodic nutrient pulses into the surface sunlit waters complemented by feeding of CO2-fixing eukaryotes on prokaryotes, i.e. bacterivory. Using the combined expertise of our research team strengthened by novel experimental approaches we will address the following questions: What is the impact of nutrient pulses on growth rates of CO2-fixing prokaryotes and eukaryotes? How do nutrient pulses affect bacterivory? Is selective feeding by CO2-fixing eukaryotes a mechanism for controlling growth of CO2-fixing prokaryotes?We will find out how general the answers to the above questions are by focusing on experimental work in the subtropical gyres of the Atlantic and Pacific Oceans, which comprise nearly three quarters of the total oligotrophic open ocean area. The three gyres we will investigate are of different geological ages and differ in composition of depleted inorganic nutrients. We will use isotopic tracers in combination with flow cytometric sorting to directly measure impact of nutrient pulses on microbial group-specific growth rates and bacterivory rates. Morphology, taxonomic identity and physiological potential of flow sorted microbial groups will be characterised by ultra-structural, molecular and metagenomic analyses. The effects of nutrient pulses on cellular biomass of CO2 fixing prokaryotes and eukaryotes will be assessed by electron microscopy of flow sorted cells coupled with energy dispersive X-ray spectroscopy. The experimental evidence will be synthesised into a generic concept to explain the mechanism of co-existence of the smallest eukaryotic and prokaryotic CO2 fixers of increasing global biogeochemical significance owing to expansion of the oligotrophic ocean under the influence of modern climate changes. Thus, the project will test the extent of inorganic nutrient control of biological CO2 fixation in the largest Earth's biome.

该提案的主要目的是解释地球上最广泛的生物群落的生态基础-在开放的贫营养海洋中，真核CO2固定器与生长更快的原核CO2固定器共存。真核生物在地球的大多数生物群落中控制着二氧化碳的固定，例如陆地、淡水和一些海洋（沿海和极地沃茨），但有一个但主要的例外：寡营养海洋环流，覆盖地球的40%。为什么尽管在环流中共同进化了数百万年，但能量上级的真核生物却无法超越原核生物？我们假设，CO2固定的真核生物和原核生物的共存是持续的情节营养脉冲到表面阳光照射的沃茨补充喂养的CO2固定的真核生物对原核生物，即bacterivory。利用我们研究团队的综合专业知识，通过新颖的实验方法，我们将解决以下问题：营养脉冲对固定二氧化碳的原核生物和真核生物的生长速率有什么影响？营养脉冲如何影响噬菌性？固定CO2的真核生物选择性摄食是控制固定CO2的原核生物生长的一种机制吗？我们将通过集中在大西洋和太平洋的亚热带环流中进行的实验工作来发现对上述问题的答案有多普遍，这些环流占贫营养开放海洋总面积的近四分之三。我们将调查的三个环流具有不同的地质年龄，并且在耗尽的无机营养物的组成上不同。我们将使用同位素示踪剂结合流式细胞仪分选直接测量营养脉冲对微生物组特异性生长速率和噬菌率的影响。将通过超微结构、分子和宏基因组分析来表征流式分选微生物组的形态、分类学身份和生理潜力。营养脉冲对固定CO2的原核生物和真核生物的细胞生物量的影响将通过流式分选细胞的电子显微镜结合能量色散X射线光谱来评估。实验证据将被合成为一个通用的概念，以解释最小的真核和原核CO2固定剂的共存机制，由于贫营养海洋的扩张，现代气候变化的影响下，全球生物地球化学的意义越来越大。因此，该项目将测试地球上最大的生物群落中无机养分对生物二氧化碳固定的控制程度。