High Throughput Technique for Screening Archaeal Tetraether Lipid Cores in Sediments as Probes of Palaeo Surface-water Temperature

筛选沉积物中古菌四醚脂质核心作为古地表水温度探针的高通量技术

• 批准号: NE/H025545/1
• 负责人: Brendan Keely
• 金额: $ 8.53万
• 依托单位: University of York
• 依托单位国家: 英国
• 项目类别: Training Grant
• 财政年份: 2010
• 资助国家: 英国
• 起止时间: 2010 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=NE%2FH025545%2F1
• 关键词: Throughput; Technique; Screening; Archaeal; Tetraether

Archaea, one of the three domains of life, were long considered to be limited to environments that exhibit extremes of temperature, pH, salinity and anoxia. Since the recognition, in the early 1990's, of archaeal gene sequences in the oceans, non-extreme archaea have been shown to be prevalent in the oceans where they fulfill important roles in the carbon and nitrogen cycles. The long term contribution of these organisms to marine element cycling is evident from the recognition of lipid structures, that are specific to the archaea and derive from their membranes, in sediments deposited around 90 million years ago. Among the lipids produced only by the archaea are structures that differ in the number of five-membered rings contained within these membrane lipid-derived components. The differences in the number of rings are believed to regulate the organisation of the membrane, allowing the organisms to adapt to different conditions, e.g. temperature, under which they grow. A particular ratio (the TEX86 index) computed from the proportions of structures with different numbers of five-membered rings that are present in marine sediments was shown to correlate very strongly with the surface water temperature of the overlying ocean, providing the potential to derive sea surface water temperatures of oceans in times past from analysis of the archaeal lipid residues preserved within sediment cores. Further investigations have identified situations where the TEX86 index shows linear trends with surface water temperature, but the values are offset by a number of degrees C. We have previously demonstrated a method using tandem mass spectrometry that differentiates different archaeal lipid structures and reveals that some of the chromatographic peaks measured for use in the TEX86 index contain isomeric structures. We plan to differentiate individual lipid structures, including isomers, using a combination of improved separation and application of tandem mass spectrometry. Hence, we will obtain much improved measurements of TEX86. At the same time, we plan to address points in the analytical approach where new strategies can be introduced to improve both the capability to detect compounds at very low levels and the speed of the overall technique for deriving the TEX86 values. Thus, we plan to develop a high throughput technique that will deliver the capacity to assess sea surface water temperatures in the past using very small sediment sample sizes and with very short analysis times. This will enable the temperature records to be generated at very high depth resolution, allowing high time resolution in the data and thereby revealing changes in temperature even over short intervals of time. The ability to generate intensive records of temperature change will be of considerable benefit to researchers concerned with understanding the nature of the marine environment in times past and its response to environmental stresses, and in developing clearer records that relate to climate change over the recent geological past (Quaternary). The method may also have application to ancient sediment sequences subject to assessment of the longer-term stability of the lipids.

古细菌是生命的三大领域之一，长期以来一直被认为仅限于极端温度、pH值、盐度和缺氧的环境。自20世纪90年代初认识到海洋中的古菌基因序列以来，非极端古菌已被证明在海洋中普遍存在，它们在碳和氮循环中发挥重要作用。这些生物对海洋元素循环的长期贡献从对古生菌特有的脂质结构的认识中可以看出，这些脂质结构来自于约9000万年前沉积的沉积物中的膜。只有古生菌产生的脂质中，有一些结构在这些膜脂质衍生成分中所含的五元环数量上不同。环数量的差异被认为可以调节膜的组织，使生物体能够适应不同的生长条件，例如温度。根据海洋沉积物中存在的具有不同数量的五元环的结构的比例计算的特定比率（TEX86指数）显示出与上覆海洋的表面水温非常强烈的相关性，提供了从沉积物芯中保存的古细菌脂质残留物分析得出过去海洋的表面水温的可能性。进一步的调查已经确定了TEX86指数与地表水温呈线性趋势的情况，但这些值被抵消了若干摄氏度。我们以前已经证明了一种方法，使用串联质谱法，区分不同的古生菌脂质结构，并揭示了一些色谱峰测量使用的TEX86指数包含异构体结构。我们计划区分个别脂质结构，包括异构体，使用改进的分离和应用串联质谱的组合。因此，我们将获得更好的TEX86测量。与此同时，我们计划解决分析方法中的一些问题，在这些问题上可以引入新的策略，以提高在非常低的水平下检测化合物的能力和获得TEX86值的整体技术的速度。因此，我们计划开发一种高通量技术，该技术将提供过去使用非常小的沉积物样本量和非常短的分析时间来评估海表面水温的能力。这将使温度记录能够以非常高的深度分辨率生成，从而允许数据中的高时间分辨率，从而即使在短时间间隔内也能显示温度的变化。能够生成温度变化的密集记录，将大大有助于研究人员了解过去海洋环境的性质及其对环境压力的反应，并有助于更清楚地记录最近地质时期（第四纪）的气候变化。该方法也可能有应用到古代沉积物序列的长期稳定性的脂质的评估。