Oxygen limitation can trigger the production of branched GDGTs in culture
Oxygen limitation can trigger the production of branched GDGTs in culture
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DOI：
10.7185/geochemlet.2132
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发表时间：
2021-01-01
影响因子：
4.9
通讯作者：
Kopf, S. H.
中科院分区：
文献类型：
--
作者：
Halamka, T. A.;McFarlin, J. M.;Kopf, S. H.
支链甘油二烷基甘油四醚（brGDGT）是普遍存在且保存良好的沉积生物标志物。这些化合物作为重要的古环境指标，由于强烈的经验之间的相关性brGDGT分布和温度和pH值在现代环境。然而，温度，pH值和brGDGT生产之间的机械联系迄今为止一直无法确定，由于缺乏明确的生物来源的brGDGT。在这里，我们报告说，氧限制触发brGDGT生产在至少一种培养的酸杆菌，并确认首次生物合成的三种结构品种的brGDGT，包括一个未表征的异构体的brGDGT Ic。这一发现有助于解释为什么brGDGT生产者如此难以识别，并为揭示brGDGT的遗传基础和生物学功能提供了一条途径，这将有助于更全面地了解其古环境意义。如果这里观察到的氧的影响更广泛地适用，基于brGDGT的温度和pH重建的经验校准目前可能会错过氧的影响，作为一个相关的，可能是主要的控制环境分布的brGDGT。
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are ubiquitous and well preserved sedimentary biomarkers. These compounds serve as important palaeoenvironmental indicators due to strong empirical correlations between brGDGT distributions and temperature and pH in modern environments. However, the mechanistic link between temperature, pH, and brGDGT production has been impossible to ascertain thus far due to the absence of a clear biological source for brGDGTs. Here, we report that oxygen limitation triggers brGDGT production in at least one cultured species of Acidobacteria and confirm for the first time the biosynthesis of three structural varieties of brGDGTs, including an uncharacterised isomer of brGDGT Ic. This discovery helps explain why brGDGT producers have been so difficult to identify and provides a pathway towards uncovering the genetic basis and biological function of brGDGTs, which will lead to a more comprehensive understanding of their palaeoenvironmental significance. If the oxygen effects observed here apply more broadly, the empirical calibrations for brGDGT-based temperature and pH reconstructions may currently be missing the effects of oxygen as a relevant and possibly dominant control in the environmental distributions of brGDGTs.