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; 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

智力优点。 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未来的高二氧化碳海洋，但它们都使用了相同有限的培养物株，并认为细胞仅短暂适应于升高的二氧化碳。然而，研究者的新结果表明，每个重18zotroph属内都存在广泛的高CO2适应性生态型。此外，在针对毛trichodesmium的初步的四年实验进化研究中，PIS在500-700代选择后通过高CO2-进行了大量的适应性反应，但以一种完全出乎意料的方式。六个复制高CO2适应的细胞系均表现出强大的N2固定速率上调。即使培养物已改回低CO2条件已有多个月，这些N2固定速率仍在继续。在这些细胞系中，NIF操纵子和N同化基因的表达也被上调，基因组的许多基因间区域的表达也是如此。研究人员假设细胞N2固定系统的本构上调可能是TrichodeSmium和Crocosphaera在扩展选择中的常见适应性反应。该项目将在一项为期四年的实验进化研究中检验这一假设，以确定这两种重18zotrophs的高CO2和低CO2专用生态型的适应性反应，以增加CO2。研究人员将在380 ppm的良好复制细胞系中，在380 ppm和750 ppm CO2的情况下，将代表性的高和低CO2适用于1000代的生态型。他们会定期执行“开关”实验，以测量在低CO2处短暂生长（一周）的高CO2选择的细胞系的N2和CO2固定速率，反之亦然。这些开关实验将允许筛选细胞系，这些细胞系在表型表达的速率参数中表现出适应性变化，例如在初步的Trichodesmium研究中观察到的。使用上一次选择期间，使用冷冻样本存档的每月，将检查其基因组，转录组和蛋白质组织的变化，将检查其基因组，转录组和蛋白质组织的变化，从而检查二氧化碳选择的细胞系中的进化机制。对这些分子和生化变化的检查将与深入的生理和生物地球化学分析进行协调。这种结合的方法将允许评估重物营养性氰基菌的潜在自适应机制，范围从indel，重复，单核苷酸多态性和换位突变，到推定的非编码RNA表达，蛋白质表达，蛋白质表达以及这些潜在的蛋白质蛋白质的影响，并将调查剂与他们的潜在机构联系起来，并将其直接联系起来。 N2和CO2固定等生物地球化学过程。最后，研究团队将确定高二氧化碳的长期选择会影响毛d和crocosposphaera的铁和磷需求，因为N2固定的本构上的上调也将对未来的两种关键营养物质在未来的高二氧化碳的限制上限制重新杂志的限制具有重大影响。该项目将支持USC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。该项目的公共教育和沟通工作将通过我们由USC资助的“ 2020”倡议赞助的年度公共宣传和专业校长来增强，旨在整合对气候变化的科学和社会反应。该项目的最大科学影响很可能是开发了一种开创性的新方法，结合了海洋科学和进化生物学，以便获得对N2固定蓝细菌的适应性反应的机械理解，以及它们控制着改变海洋化学和气候变化的生物地球化学周期