Schneider Hans, Lai Bin, Krömer Jens O
Systems Biotechnology Group, Department Microbial Biotechnology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, 04318, Germany.
BMBF Junior Research Group Biophotovoltaics, Department Microbial Biotechnology, Helmholtz Centre for Environmental Research - UFZ, Leipzig, 04318, Germany.
Plant J. 2025 Jan;121(2):e17225. doi: 10.1111/tpj.17225.
Biophotovoltaics offers a promising low-carbon footprint approach to utilize solar energy. It aims to couple natural oxygenic photosynthetic electrons to an external electron sink. This lays the foundation for a potentially high light-to-energy efficiency of the Biophotovoltaic process. However, there are still uncertainties around demonstrating the direct coupling of electron fluxes between photosystems and the external electrode. The dynamic cellular electron transfer network linked to physiological and environmental parameters poses a particular challenge here. In this work, the active cellular electron transfer network was modulated by tuning the cultivating conditions of Synechocystis and the operating conditions in Biophotovoltaics. The current output during darkness was found to be determined by the intracellular glycogen levels. Minimizing the intracellular glycogen pools also eliminated the dark-current output. Moreover, our results provide strong evidence that water splitting in photosystem II is the electron source enabling photocurrent, bypassing the microbe's metabolism. Eliminating the storage carbon as possible source of electrons did not reduce the specific photocurrent output, indicating an efficient coupling of photosynthetic electron flux to the anode. Furthermore, inhibiting respiration on the one hand increased the photocurrent and on the other hand showed a negative effect on the dark-current output. This suggested a switchable role of the respiratory electron transfer chain in the extracellular electron transfer pathway. Overall, we conclude that Synechocystis dynamically switches electron sources and utilizes different extracellular transfer pathways for the current output toward the external electron sink, depending on the physiological and environmental conditions.
生物光伏提供了一种利用太阳能的具有前景的低碳足迹方法。它旨在将自然的产氧光合作用电子与外部电子受体耦合。这为生物光伏过程潜在的高光能转换效率奠定了基础。然而，在证明光系统与外部电极之间电子通量的直接耦合方面仍存在不确定性。与生理和环境参数相关的动态细胞电子传递网络在此构成了特殊挑战。在这项工作中，通过调节集胞藻的培养条件和生物光伏中的操作条件来调控活跃的细胞电子传递网络。发现黑暗期间的电流输出由细胞内糖原水平决定。使细胞内糖原池最小化也消除了暗电流输出。此外，我们的结果提供了有力证据，表明光系统II中的水分解是产生光电流的电子来源，绕过了微生物的代谢。消除作为可能电子来源的储存碳并没有降低比光电流输出，表明光合电子通量与阳极有效耦合。此外，一方面抑制呼吸增加了光电流，另一方面对暗电流输出显示出负面影响。这表明呼吸电子传递链在细胞外电子传递途径中具有可切换的作用。总体而言，我们得出结论，集胞藻根据生理和环境条件动态切换电子来源，并利用不同的细胞外传递途径向外部电子受体输出电流。
