Sun Cheng, Yu Qilin, Zhao Zhiqiang, Zhang Yaobin
Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
Key Laboratory of Industrial Ecology and Environmental Engineering (Dalian University of Technology), Ministry of Education, School of Environmental Science and Technology, Dalian University of Technology, Dalian 116024, China.
Sci Total Environ. 2022 Nov 25;849:157864. doi: 10.1016/j.scitotenv.2022.157864. Epub 2022 Aug 4.
As a vital part of the global carbon cycle, photosynthesis helps in fixing CO to produce diverse biomass. However, over-reliance on optical density results in inadequate photosynthesis under limited light sources. The coupling of extracellular respiration and photosynthetic chain via the quinone pool provides a possibility for electrically driven photosynthesis in darkness, which is not well understood. In this study, CO fixation of photosynthetic bacteria Rhodopseudomonas palustris was enhanced in the dark via extracellular electron uptake from the electrode at -0.4 V. The copy number of R. palustris increased by 35 folds during 28 days of operation, accompanied by the increase of ATP content, NADH/NAD, and NADPH/NADP of cells. Especially, the activity of Rubisco, the key enzyme of the Calvin cycle, increased by 28 % during electro-cultivation. Accordingly, the electrochemical activity of R. palustris was found to increase, which might be attributed to the structural modification of protein-like substances due to the enhanced proton-coupled electron transfer (PCET) process in electro-cultivation, which was further confirmed by in situ Fourier transform infrared spectroscopy and kinetic isotope effect tests. This study indicated that extracellular respiration could be electrostimulated via PCET to maintain photosynthesis in R. palustris in the dark.
作为全球碳循环的重要组成部分，光合作用有助于固定二氧化碳以产生各种生物质。然而，过度依赖光密度会导致在有限光源下光合作用不足。通过醌池将细胞外呼吸与光合链耦合为黑暗中电驱动光合作用提供了一种可能性，但对此了解并不充分。在本研究中，通过在-0.4 V时从电极摄取细胞外电子，黑暗中光合细菌沼泽红假单胞菌的二氧化碳固定得到增强。在运行28天期间，沼泽红假单胞菌的拷贝数增加了35倍，同时细胞的ATP含量、NADH/NAD和NADPH/NADP增加。特别是，卡尔文循环的关键酶核酮糖-1,5-二磷酸羧化酶/加氧酶（Rubisco）的活性在电培养期间增加了28%。相应地，发现沼泽红假单胞菌的电化学活性增加，这可能归因于电培养中质子耦合电子转移（PCET）过程增强导致的类蛋白质物质的结构修饰，原位傅里叶变换红外光谱和动力学同位素效应测试进一步证实了这一点。本研究表明，细胞外呼吸可通过PCET被电刺激，以在黑暗中维持沼泽红假单胞菌的光合作用。
