Microbes are known to accumulate intracellular SiO₂(aq) up to 100s of mmol/l from modern seawater (SiO₂(aq) <100 µmol/l), despite having no known nutrient requirement for Si. Before the evolution of siliceous skeletons, marine silica concentrations were likely an order of magnitude higher than the modern ocean, raising the possibility that intracellular SiO₂(aq) accumulation interfered with normal cellular function in non-silicifying algae. Yet, because few culturing studies have isolated the effects of SiO₂(aq) at high concentration, the potential impact of elevated marine silica on early microbial evolution is unknown. Here, we test the influence of elevated SiO₂(aq) on eukaryotic algae, as well as a prokaryote species. Our results demonstrate that under SiO₂(aq) concentrations relevant to ancient seawater, intracellular Si accumulates to concentrations comparable to those found in siliceous algae such as diatoms. In addition, all eukaryotic algae showed a statistically significant response to the high-Si treatment, including reduced average cell sizes and/or a reduction in the maximum growth rate. In contrast, there was no consistent response to the high-Si treatment by the prokaryote species. Our results highlight the possibility that elevated marine SiO₂(aq) may have been an environmental stressor during early eukaryotic evolution.

中文翻译：

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SiO2(aq)升高对细胞内二氧化硅吸收和微生物代谢的影响

已知微生物会从现代海水（SiO ₂ ( aq ) <100 µmol/l）中积累高达 100 mmol/l 的细胞内 SiO ₂ ( aq )，尽管对 Si 没有已知的营养需求。在硅质骨架进化之前，海洋二氧化硅浓度可能比现代海洋高一个数量级，这增加了细胞内 SiO ₂ ( aq ) 积累干扰非硅化藻类正常细胞功能的可能性。然而，由于很少有培养研究分离出 SiO ₂ ( aq) 在高浓度下，升高的海洋二氧化硅对早期微生物进化的潜在影响是未知的。在这里，我们测试了升高的 SiO ₂ ( aq ) 对真核藻类以及原核生物物种的影响。我们的结果表明，在 SiO ₂ ( aq) 与古代海水相关的浓度，细胞内的 Si 积累到与硅藻等硅藻中发现的浓度相当的浓度。此外，所有真核藻类对高硅处理均表现出统计学上的显着响应，包括平均细胞尺寸减小和/或最大生长速率降低。相比之下，原核生物物种对高硅处理没有一致的反应。我们的结果强调了在早期真核生物进化过程中升高的海洋 SiO ₂ ( aq ) 可能是环境压力源的可能性。