Department of Biological Sciences, University of Southern California, Los Angeles, California, USA.
Climate Change Cluster, University of Technology Sydney, Ultimo, New South Wales, Australia.
Glob Chang Biol. 2022 Oct;28(19):5741-5754. doi: 10.1111/gcb.16330. Epub 2022 Jul 20.
Despite their relatively high thermal optima (T ), tropical taxa may be particularly vulnerable to a rising baseline and increased temperature variation because they live in relatively stable temperatures closer to their T . We examined how microbial eukaryotes with differing thermal histories responded to temperature fluctuations of different amplitudes (0 control, ±2, ±4°C) around mean temperatures below or above their T . Cosmopolitan dinoflagellates were selected based on their distinct thermal traits and included two species of the same genus (tropical and temperate Coolia spp.), and two strains of the same species maintained at different temperatures for >500 generations (tropical Amphidinium massartii control temperature and high temperature, CT and HT, respectively). There was a universal decline in population growth rate under temperature fluctuations, but strains with narrower thermal niche breadth (temperate Coolia and HT) showed ~10% greater reduction in growth. At suboptimal mean temperatures, cells in the cool phase of the fluctuation stopped dividing, fixed less carbon (C) and had enlarged cell volumes that scaled positively with elemental C, N, and P and C:Chlorophyll-a. However, at a supra-optimal mean temperature, fixed C was directed away from cell division and novel trait combinations developed, leading to greater phenotypic diversity. At the molecular level, heat-shock proteins, and chaperones, in addition to transcripts involving genome rearrangements, were upregulated in CT and HT during the warm phase of the supra-optimal fluctuation (30 ± 4°C), a stress response indicating protection. In contrast, the tropical Coolia species upregulated major energy pathways in the warm phase of its supra-optimal fluctuation (25 ± 4°C), indicating a broadscale shift in metabolism. Our results demonstrate divergent effects between taxa and that temporal variability in environmental conditions interacts with changes in the thermal mean to mediate microbial responses to global change, with implications for biogeochemical cycling.
尽管它们的热最佳温度相对较高（T），热带分类单元可能特别容易受到基线上升和温度变化增加的影响，因为它们生活在接近其 T 的相对稳定的温度下。我们研究了具有不同热历史的微生物真核生物如何应对平均温度以下或以上的不同幅度（0 对照、±2、±4°C）的温度波动。选择了具有不同热特征的世界性甲藻，包括同一属的两个物种（热带和温带的 Coolia spp.），以及在不同温度下维持超过 500 代的同一物种的两个菌株（热带 Amphidinium massartii 对照温度和高温，CT 和 HT）。在温度波动下，种群增长率普遍下降，但热生态位较窄的菌株（温带 Coolia 和 HT）的生长减少约 10%。在非最适平均温度下，波动冷相中的细胞停止分裂，固定的碳（C）较少，细胞体积增大，与元素 C、N、P 和 C：叶绿素 a 呈正相关。然而，在超最适平均温度下，固定的 C 被引导离开细胞分裂，并形成新的特征组合，导致表型多样性增加。在分子水平上，热休克蛋白和伴侣蛋白，以及涉及基因组重排的转录物，在 CT 和 HT 中在上调在超最适波动的暖相（30±4°C）期间，这是一种应激反应，表明有保护作用。相比之下，热带 Coolia 物种在其超最适波动的暖相（25±4°C）中上调了主要的能量途径，表明代谢发生了广泛的转变。我们的结果表明，分类单元之间存在不同的影响，并且环境条件的时间变异性与热均值的变化相互作用，介导微生物对全球变化的反应，对生物地球化学循环有影响。
