The thermoacidophilic red alga Cyanidioschyzon merolae survives its challenging environment likely in part by operating a carbon-concentrating mechanism (CCM). Here, we demonstrated that C. merolae's cellular affinity for CO2 is stronger than the affinity of its rubisco for CO2. This finding provided additional evidence that C. merolae operates a CCM while lacking the structures and functions characteristic of CCMs in other organisms. To test how such a CCM could function, we created a mathematical compartmental model of a simple CCM, distinct from those we have seen previously described in detail. The results of our modeling supported the feasibility of this proposed minimal and non-canonical CCM in C. merolae. To facilitate the robust modeling of this process, we measured and incorporated physiological and enzymatic parameters into the model. Additionally, we trained a surrogate machine-learning model to emulate the mechanistic model and characterized the effects of model parameters on key outputs. This parameter exploration enabled us to identify model features that influenced whether the model met the experimentally derived criteria for functional carbon concentration and efficient energy usage. Such parameters included cytosolic pH, bicarbonate pumping cost and kinetics, cell radius, carboxylation velocity, number of thylakoid membranes, and CO2 membrane permeability. Our exploration thus suggested that a non-canonical CCM could exist in C. merolae and illuminated the essential features generally necessary for CCMs to function.

中文翻译：

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使用不确定性量化建模揭示了非规范藻类碳浓缩机制的基本要素


嗜热酸性红藻 Cyanidioschyzon merolae 在其具有挑战性的环境中幸存下来，部分原因可能是通过运行碳浓缩机制 （CCM）。在这里，我们证明了 C. merolae 对 CO2 的细胞亲和力强于其 rubisco 对 CO2 的亲和力。这一发现提供了额外的证据，表明 C. merolae 在 CCM 中操作 CCM，同时缺乏其他生物体中 CCM 的结构和功能特征。为了测试这种 CCM 的工作原理，我们创建了一个简单 CCM 的数学区室模型，与我们之前详细描述的模型不同。我们的建模结果支持了这种提出的在 C. merolae 中的最小和非经典 CCM 的可行性。为了促进这一过程的稳健建模，我们测量了生理和酶参数并将其纳入模型。此外，我们还训练了一个替代机器学习模型来模拟机理模型，并表征了模型参数对关键输出的影响。这种参数探索使我们能够确定影响模型是否满足实验得出的功能性碳浓度和有效能源利用标准的模型特征。这些参数包括胞质 pH 值、碳酸氢盐泵送成本和动力学、细胞半径、羧化速度、类囊体膜数量和 CO2 膜通透性。因此，我们的探索表明 C. merolae 中可能存在非经典 CCM，并阐明了 CCM 发挥作用通常需要的基本特征。