Collaborative research: Adaptation of key N2-fixing cyanobacteria to changing CO2

合作研究：关键固氮蓝细菌对二氧化碳变化的适应

• 批准号: 1260490
• 负责人: David Hutchins
• 金额: $ 149.84万
• 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: 2013
• 资助国家: 美国
• 起止时间: 2013-03-01 至 2018-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1260490&HistoricalAwards=false
• 关键词: Collaborative; research; Adaptation; key; N2

Intellectual Merit. This study will employ a novel combination of experimental evolution techniques and state-of-the-art molecular methods to yield unique insights into adaptive changes in the keystone marine cyanobacteria Trichodesmium and Crocosphaera in response to selection by high CO2 Several studies have suggested that N2-fixation rates of the biogeochemically-critical cyanobacteria Trichodesmium and Crocosphaera may increase dramatically in the future high CO2 ocean, but these have all used the same limited set of cultured isolates and considered cells only briefly acclimated to elevated CO2. The investigator's new results, however, demonstrate that a broad diversity of high- and low-CO2 adapted ecotypes exists within each diazotroph genus. Furthermore, in a preliminary four year experimental evolution study with Trichodesmium, the PIs observed large adaptive responses following 500-700 generations of selection by high CO2- but in a completely unexpected way. All of the six replicate high CO2-adapted cell lines exhibited strong constitutive up-regulation of N2 fixation rates. These very elevated N2 fixation rates continued, even though the cultures have were switched back to low-CO2 conditions for many months. Expression of the nif operon and N assimilatory genes was also up-regulated in these cell lines, as is expression of many intergenic regions of the genome. The investigators hypothesize that constitutive up-regulation of cellular N2 fixation systems may be a common adaptive response of both Trichodesmium and Crocosphaera under extended selection by elevated CO2. This project will test this hypothesis in a four-year experimental evolution study to determine the adaptive responses of both high- and low-CO2 specialized ecotypes of these two diazotrophs to increased CO2. The investigators will grow representative high- and low-CO2 adapted ecotypes from each genus in well-replicated cell lines at 380 ppm and 750 ppm CO2 for up to 1000 generations. Periodically, they will perform "switch" experiments to measure N2 and CO2 fixation rates and growth rates of high CO2-selected cell lines grown briefly (one week) at low CO2, and vice versa. These switch experiments will allow screening for cell lines which exhibit adaptive changes in phenotypically-expressed rate parameters, such as those observed in the preliminary Trichodesmium study. Evolutionary mechanisms in the CO2-selected cell lines will be examined by comparison of changes in their genomes, transcriptomes, and proteomes over time relative to reference genomes, using frozen samples archived monthly during the preceding selection period. Examination of these molecular and biochemical changes will be coordinated with an in-depth array of physiological and biogeochemical analyses. This combined approach will allow an evaluation of potential adaptive mechanisms in diazotrophic cyanobacteria ranging from indel, duplication, single nucleotide polymorphism, and transposition mutations to altered putative non-coding RNA expression, protein expression, and post-translational protein modifications, and then allow the investigators to link these mechanisms directly with their potential impacts on ecosystem-level biogeochemical processes like N2 and CO2 fixation. Finally, the research team will determine how long term selection by high CO2 affects the iron and phosphorus requirements of Trichodesmium and Crocosphaera, since constitutive up-regulation of N2 fixation would also have major implications for limitation of diazotrophs by these two critical nutrients in the future high CO2 ocean.Broader Impacts. This project will support graduate student dissertation work at USC and WHOI, as well as research activities by under-represented undergraduate biology majors. Public education and communication efforts for this project will be enhanced by an annual series of public outreach and professional colloquia sponsored by our USC-funded "2020" initiative intended to integrate scientific and societal responses to climate change. The biggest scientific impact of this project may well be the development of a pioneering new approach combining marine science and evolutionary biology, in order to obtain a mechanistic understanding of the adaptive responses of N2-fixing cyanobacteria and the key biogeochemical cycles that they control to changing ocean chemistry and climate

知识价值。本研究将采用实验进化技术和最先进的分子方法相结合的新方法，对关键的海洋蓝藻Trichodesmium和Crocosphaera在高二氧化碳选择下的适应性变化产生独特的见解。几项研究表明，生物地球化学关键的蓝藻Trichodesmium和Crocosphaera的n2固定率可能在未来的高二氧化碳海洋中急剧增加。但这些研究都使用了同样有限的培养分离物，并且认为细胞只是短暂地适应了升高的二氧化碳。然而，研究者的新结果表明，在每个重氮养菌属中存在着广泛的高和低二氧化碳适应生态型的多样性。此外，在对Trichodesmium进行的一项为期四年的初步实验进化研究中，pi观察到在高二氧化碳的500-700代选择之后，出现了很大的适应性反应——但以一种完全出乎意料的方式。所有6个重复的高co2适应性细胞系均表现出N2固定率的强组成上调。这些非常高的N2固定率继续存在，即使培养物已经切换回低二氧化碳条件好几个月了。nif操纵子和N同化基因的表达也在这些细胞系中上调，基因组的许多基因间区域的表达也是如此。研究人员推测，细胞内N2固定系统的结构性上调可能是trichodesium和Crocosphaera在二氧化碳升高的长期选择下共同的适应性反应。该项目将在为期四年的实验进化研究中验证这一假设，以确定这两种重氮营养体的高二氧化碳和低二氧化碳特化生态型对增加的二氧化碳的适应性反应。研究人员将在380 ppm和750 ppm的二氧化碳浓度下，在复制良好的细胞系中培养具有代表性的高二氧化碳和低二氧化碳适应生态型，最多可达1000代。他们将定期进行“切换”实验，测量在低二氧化碳条件下短暂生长（一周）的高二氧化碳选择细胞系的N2和CO2固定率和生长率，反之亦然。这些开关实验将允许筛选在表型表达率参数中表现出适应性变化的细胞系，例如在初步的Trichodesmium研究中观察到的那些细胞系。在二氧化碳选择细胞系的进化机制将通过比较其基因组、转录组和蛋白质组随时间相对于参考基因组的变化来进行研究，使用在前选择期间每月存档的冷冻样本。这些分子和生化变化的检查将与一系列深入的生理和生物地球化学分析相协调。这种结合的方法将允许评估重氮营养蓝藻的潜在适应机制，包括indel、重复、单核苷酸多态性和转座突变，以及假设的非编码RNA表达、蛋白质表达和翻译后蛋白质修饰的改变，然后允许研究人员将这些机制直接与它们对生态系统水平的生物地球化学过程（如N2和CO2固定）的潜在影响联系起来。最后，研究小组将确定高二氧化碳的长期选择如何影响Trichodesmium和Crocosphaera对铁和磷的需求，因为在未来的高二氧化碳海洋中，N2固定的组成上调也将对这两种关键营养物质对重氮营养物的限制产生重大影响。更广泛的影响。该项目将支持南加州大学和WHOI的研究生论文工作，以及代表性不足的本科生物学专业的研究活动。南加州大学资助的“2020”计划旨在整合科学和社会对气候变化的反应，将通过每年一系列的公众宣传和专业座谈会来加强该项目的公众教育和沟通工作。该项目最大的科学影响可能是开发了一种开创性的结合海洋科学和进化生物学的新方法，以获得对固氮蓝藻的适应性反应及其控制的关键生物地球化学循环的机制理解，以改变海洋化学和气候

项目成果

Comment on “The complex effects of ocean acidification on the prominent N 2 -fixing cyanobacterium Trichodesmium ”

评论 – 海洋酸化对重要的 N 2 固定蓝藻 Trichodesmium 的复杂影响 –

• DOI: 10.1126/science.aao0067
• 发表时间: 2017
• 期刊: Science
• 影响因子: 56.9
• 作者: Hutchins, David A.;Fu, Feixue;Walworth, Nathan G.;Lee, Michael D.;Saito, Mak A.;Webb, Eric A.
• 通讯作者: Webb, Eric A.

Nutrient-Colimited Trichodesmium as a Nitrogen Source or Sink in a Future Ocean

• DOI: 10.1128/aem.02137-17
• 发表时间: 2018-02-01
• 期刊: APPLIED AND ENVIRONMENTAL MICROBIOLOGY
• 影响因子: 4.4
• 作者: Walworth, Nathan G.;Fu, Fei-Xue;Hutchins, David A.
• 通讯作者: Hutchins, David A.

Responses of the large centric diatom Coscinodiscus sp. to interactions between warming, elevated CO 2 , and nitrate availability: Diatom responses to climate changes

大中心硅藻 Coscinodiscus sp 的响应。

• DOI: 10.1002/lno.10781
• 发表时间: 2018
• 期刊: Limnology and Oceanography
• 影响因子: 4.5
• 作者: Qu, Pingping;Fu, Feixue;Hutchins, David A.
• 通讯作者: Hutchins, David A.

Transcriptional Activities of the Microbial Consortium Living with the Marine Nitrogen-Fixing Cyanobacterium Trichodesmium Reveal Potential Roles in Community-Level Nitrogen Cycling

与海洋固氮蓝藻Trichodesmium一起生活的微生物群落的转录活性揭示了群落水平氮循环的潜在作用

• DOI: 10.1128/aem.02026-17
• 发表时间: 2017
• 期刊: Applied and Environmental Microbiology
• 影响因子: 4.4
• 作者: Lee, Michael D.;Webb, Eric A.;Walworth, Nathan G.;Fu, Fei-Xue;Held, Noelle A.;Saito, Mak A.;Hutchins, David A.;Drake, Harold L.
• 通讯作者: Drake, Harold L.

Adaptive evolution in the coccolithophore Gephyrocapsa oceanica following 1,000 generations of selection under elevated CO 2

高CO 2 条件下颗石藻Gephyrocapsa oceanica经过1,000代选择后的适应性进化

• DOI: 10.1111/gcb.14065
• 发表时间: 2018
• 期刊: Global Change Biology
• 影响因子: 11.6
• 作者: Tong, Shanying;Gao, Kunshan;Hutchins, David A.
• 通讯作者: Hutchins, David A.