Chrachri Abdul, Hopkinson Brian M, Flynn Kevin, Brownlee Colin, Wheeler Glen L
Marine Biological Association, Plymouth, PL1 2PB, UK.
Department of Marine Sciences, University of Georgia, Athens, 30602-3636, GA, USA.
Nat Commun. 2018 Jan 8;9(1):74. doi: 10.1038/s41467-017-02426-y.
Photosynthesis by marine diatoms plays a major role in the global carbon cycle, although the precise mechanisms of dissolved inorganic carbon (DIC) uptake remain unclear. A lack of direct measurements of carbonate chemistry at the cell surface has led to uncertainty over the underlying membrane transport processes and the role of external carbonic anhydrase (eCA). Here we identify rapid and substantial photosynthesis-driven increases in pH and [CO] primarily due to the activity of eCA at the cell surface of the large diatom Odontella sinensis using direct simultaneous microelectrode measurements of pH and CO along with modelling of cell surface inorganic carbonate chemistry. Our results show that eCA acts to maintain cell surface CO concentrations, making a major contribution to DIC supply in O. sinensis. Carbonate chemistry at the cell surface is therefore highly dynamic and strongly dependent on cell size, morphology and the carbonate chemistry of the bulk seawater.
海洋硅藻的光合作用在全球碳循环中起着重要作用，尽管溶解无机碳（DIC）吸收的确切机制仍不清楚。由于缺乏对细胞表面碳酸盐化学的直接测量，导致对潜在的膜运输过程以及外部碳酸酐酶（eCA）的作用存在不确定性。在这里，我们通过对pH值和CO的直接同步微电极测量以及细胞表面无机碳酸盐化学建模，确定了大型硅藻中华盒形藻细胞表面主要由于eCA的活性而导致的由光合作用驱动的pH值和[CO]的快速大幅增加。我们的结果表明，eCA起到维持细胞表面CO浓度的作用，对中华盒形藻的DIC供应做出了主要贡献。因此，细胞表面的碳酸盐化学是高度动态的，并且强烈依赖于细胞大小、形态以及大量海水的碳酸盐化学性质。
