Müller Stefan, Zavřel Tomáš, Červený Jan
Faculty of Mathematics University of Vienna Wien Austria.
Department of Adaptive Biotechnologies Global Change Research Institute of the Czech Academy of Sciences Brno Czech Republic.
Eng Life Sci. 2019 Oct 31;19(12):955-967. doi: 10.1002/elsc.201900061. eCollection 2019 Dec.
Photosynthetic organisms developed various strategies to mitigate high light stress. For instance, aquatic organisms are able to spend excessive energy by exchanging dissolved CO (dCO) and bicarbonate ( ) with the environment. Simultaneous uptake and excretion of the two carbon species is referred to as inorganic carbon cycling. Often, inorganic carbon cycling is indicated by displacements of the extracellular dCO signal from the equilibrium value after changing the light conditions. In this work, we additionally use (i) the extracellular pH signal, which requires non- or weakly-buffered medium, and (ii) a dynamic model of carbonate chemistry in the aquatic environment to detect and quantitatively describe inorganic carbon cycling. Based on simulations and experiments in precisely controlled photobioreactors, we show that the magnitude of the observed dCO displacement crucially depends on extracellular pH level and buffer concentration. Moreover, we find that the dCO displacement can also be caused by simultaneous uptake of both dCO and (no inorganic carbon cycling). In a next step, the dynamic model of carbonate chemistry allows for a quantitative assessment of cellular dCO, , and H exchange rates from the measured dCO and pH signals. Limitations of the method are discussed.
光合生物进化出了多种策略来减轻高光胁迫。例如，水生生物能够通过与环境交换溶解的二氧化碳（dCO）和碳酸氢根（ ）来消耗多余的能量。两种碳物种的同时摄取和排泄被称为无机碳循环。通常，无机碳循环通过在改变光照条件后细胞外dCO信号偏离平衡值来指示。在这项工作中，我们还使用了（i）细胞外pH信号，这需要非缓冲或弱缓冲介质，以及（ii）水生环境中碳酸盐化学的动态模型来检测和定量描述无机碳循环。基于在精确控制的光生物反应器中的模拟和实验，我们表明观察到的dCO位移的大小关键取决于细胞外pH水平和缓冲浓度。此外，我们发现dCO位移也可能由dCO和 的同时摄取引起（无无机碳循环）。下一步，碳酸盐化学的动态模型允许根据测量的dCO和pH信号对细胞的dCO、 和H交换速率进行定量评估。我们还讨论了该方法的局限性。
