Liu Wei, Wu Yundang, Liu Tongxu, Li Fangbai, Dong Hui, Jing Meiqing
College of Materials and Energy, South China Agricultural University, Guangzhou, China.
Guangdong Key Laboratory of Integrated Agro-Environmental Pollution Control and Management, Guangdong Institute of Eco-Environmental Science and Technology, Guangzhou, China.
Front Microbiol. 2019 Mar 6;10:464. doi: 10.3389/fmicb.2019.00464. eCollection 2019.
The electron shuttling process has been recognized as an important microbial respiration process. Because the incubation temperature can influence both the reactivity of electron mediators and cell growth, it may also affect the electron-shuttle-mediated extracellular electron transfer (EET) process. Here, the effect of incubation temperature (22-38°C) was investigated in a bioelectrochemical system (BES) using MR-1 and 50 μM of 9,10-anthraquinone-2-sulfonate (AQS). We found that current generation increased as the temperature was increased from 22 to 34°C and then decreased sharply at 38°C. The biofilm biomass, as indicated by the total protein extracted from the electrode, increased as the temperature increased from 22 to 34°C and then decreased at 38°C, mirroring the current generation results. These results were further confirmed by increasing the temperature slowly, step-by-step, in a single BES with a constant biofilm biomass, suggesting that the EET rates could be substantially influenced by temperature, even with the same biofilm. The effects of temperature on the AQS bioreduction rate, -type cytochrome (-Cyts)-bound-cofactor-mediated EET, the AQS mid-point potential, and the AQS diffusion coefficient were studied. From these results, we were able to conclude that temperature influenced the EET rates by changing the -Cyts-bound-cofactor-mediated EET process and the AQS bioreduction rate, and that the change in biofilm formation was a dominant factor influencing the overall EET rates. These findings should contribute to the fundamental understanding of EET processes. Moreover, optimization of the operating parameters for current generation will be helpful for the practical application of bioelectrochemical techniques.
电子穿梭过程已被认为是一种重要的微生物呼吸过程。由于培养温度会影响电子介质的反应性和细胞生长，它也可能影响电子穿梭介导的细胞外电子转移（EET）过程。在此，利用MR-1和50μM的9,10-蒽醌-2-磺酸盐（AQS），在生物电化学系统（BES）中研究了培养温度（22-38°C）的影响。我们发现，随着温度从22°C升高到34°C，电流生成增加，然后在38°C时急剧下降。如从电极提取的总蛋白所示，生物膜生物量随着温度从22°C升高到34°C而增加，然后在38°C时下降，这与电流生成结果一致。通过在具有恒定生物膜生物量的单个BES中逐步缓慢升高温度，进一步证实了这些结果，这表明即使生物膜相同，EET速率也可能受到温度的显著影响。研究了温度对AQS生物还原速率、-型细胞色素（-Cyts）结合辅因子介导的EET、AQS中点电位和AQS扩散系数的影响。从这些结果中，我们能够得出结论，温度通过改变-Cyts结合辅因子介导的EET过程和AQS生物还原速率来影响EET速率，并且生物膜形成的变化是影响整体EET速率的主要因素。这些发现将有助于从根本上理解EET过程。此外，优化电流生成的操作参数将有助于生物电化学技术的实际应用。
