Kumar Santosh, Rechav Katya, Kaplan-Ashiri Ifat, Gal Assaf
Department of Plant and Environmental Sciences, Weizmann Institute of Science, Rehovot, Israel.
Department of Chemical Research Support, Weizmann Institute of Science, Rehovot, Israel.
Sci Adv. 2020 Oct 16;6(42). doi: 10.1126/sciadv.aaz7554. Print 2020 Oct.
Diatoms are an abundant group of microalgae, known for their ability to form an intricate cell wall made of silica. Silicon levels in seawater are in the micromolar range, making it a challenge for diatoms to supply the rapid intracellular silicification process with the needed flux of soluble silicon. Here, we use three-dimensional cryo-electron microscopy and spectroscopy to quantitatively analyze, at submicrometer spatial resolution and sensitivity in the millimolar range, intracellular silicon in diatom cells. Our results show that the internal silicon concentration inside the cell is ~150 mM in average, three orders of magnitude higher than the external environment. The cellular silicon content is not compartmentalized, but rather unevenly distributed throughout the cell. Unexpectedly, under silicon starvation, the internal silicon pool is not depleted, reminiscent of a constitutive metabolite. Our spatially resolved approach to analyze intracellular silicon opens avenues to investigate this homeostatic trait of diatoms.
硅藻是一类数量丰富的微藻，以其能够形成由二氧化硅构成的复杂细胞壁而闻名。海水中的硅含量处于微摩尔范围内，这使得硅藻难以向快速的细胞内硅化过程提供所需的可溶性硅通量。在此，我们使用三维冷冻电子显微镜和光谱学，在亚微米空间分辨率和毫摩尔范围内的灵敏度下，对硅藻细胞内的硅进行定量分析。我们的结果表明，细胞内部的硅平均浓度约为150 mM，比外部环境高三个数量级。细胞内的硅含量并非被分隔开，而是在整个细胞中分布不均。出乎意料的是，在硅饥饿条件下，细胞内的硅库并未耗尽，这让人联想到一种组成型代谢物。我们用于分析细胞内硅的空间分辨方法为研究硅藻的这种稳态特性开辟了道路。
