College of Life Science, Northeast Forestry University, Harbin, China.
Appl Microbiol Biotechnol. 2022 Sep;106(18):6253-6262. doi: 10.1007/s00253-022-12120-9. Epub 2022 Aug 15.
Electronic exchanges occur between semiconductor minerals and microorganisms. However, researchers have focused on the photocatalytic degradation of pollutants by semiconductor minerals, and there is a limited amount of studies on semiconductor photogenerated electrons that influence the growth and energetic mechanisms of bacteria. Bioelectrochemical systems (BES) are important new bioengineering technologies for investigating the mechanisms by which bacteria absorb electrons. In this work, we built a BES that used α-FeO nanorods as a photoanode and Citrobacter freundii as bio-cathode bacteria to explore the effect of photoelectrons on C. freundii growth and metabolism. The photoanode was prepared by a hydrothermal synthesis method. As confirmed by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS), the photoanode was made of α-FeO. Corresponding scanning electron microscope (SEM) images showed that α-FeO nanorod arrays formed with a diameter of 50 nm, and the band gap was 2.03 eV, as indicated by UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The C. freundii growth metabolism changed significantly because of photoelectrons; under light conditions, the growth rate of C. freundii significantly accelerated, and as inferred from the three-dimensional fluorescence spectrum, the protein, humic acid, and NADH concentrations were significantly higher at 72 h. According to the changes in the organic acid content, photoelectrons participated in the reductive tricarboxylic acid cycle (rTCA) to enhance growth and metabolism. The results of the study have broad implications for advancing fields that study the effects of semiconductor minerals on electroactive microorganisms and the semiconductor-photoelectronic transport mechanisms of electroautotrophic microorganisms. KEY POINTS: • For the first time, A BES was built that used α-Fe2O3 nanorods as a photoanode and C. freundii as a bio-cathode bacteria. • Photoelectrons produced by α-Fe2O3 photoelectrode promote the growth of C. freundii. • Effects of photoelectrons on C. freundii metabolism were conjectured by the changes of organic acids and NADH.
电子在半导体矿物和微生物之间发生交换。然而，研究人员专注于半导体矿物对污染物的光催化降解，而对影响细菌生长和能量机制的半导体光生电子的研究则有限。生物电化学系统（BES）是研究细菌吸收电子机制的重要新型生物工程技术。在这项工作中，我们构建了一个 BES，使用α-FeO 纳米棒作为光阳极和弗氏柠檬酸杆菌作为生物阴极细菌，以探索光电子对 C. freundii 生长和代谢的影响。光阳极通过水热合成法制备。X 射线衍射（XRD）和 X 射线光电子能谱（XPS）证实光阳极由α-FeO 组成。相应的扫描电子显微镜（SEM）图像显示，α-FeO 纳米棒阵列的直径为 50nm，带隙为 2.03eV，如紫外可见漫反射光谱（UV-vis DRS）所示。由于光电子的作用，C. freundii 的生长代谢发生了显著变化；在光照条件下，C. freundii 的生长速度明显加快，根据三维荧光光谱推断，72h 时蛋白质、腐殖酸和 NADH 的浓度明显更高。根据有机酸含量的变化，光电子参与还原三羧酸循环（rTCA），以增强生长和代谢。该研究的结果对推进研究半导体矿物对电活性微生物的影响以及电自养微生物的半导体光电输运机制的领域具有广泛的意义。 要点： • 首次构建了一个使用α-Fe2O3纳米棒作为光阳极和 C. freundii 作为生物阴极细菌的 BES。 • α-Fe2O3 光电极产生的光电子促进了 C. freundii 的生长。 • 通过有机酸和 NADH 的变化推测了光电子对 C. freundii 代谢的影响。
