Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, United Kingdom.
Department of Chemistry, Université de Montréal, Roger-Gaudry Building, Montreal, Quebec H3C 3J7, Canada.
J Am Chem Soc. 2020 Mar 18;142(11):5194-5203. doi: 10.1021/jacs.9b13077. Epub 2020 Mar 4.
Extracellular electron transfer (EET) in microorganisms is prevalent in nature and has been utilized in functional bioelectrochemical systems. EET of has been extensively studied and has been revealed to be facilitated through -type cytochromes, which mediate charge between the electrode and in anodic mode. However, the EET pathway of cathodic conversion of fumarate to succinate is still under debate. Here, we apply a variety of analytical methods, including electrochemistry, UV-vis absorption and resonance Raman spectroscopy, quartz crystal microbalance with dissipation, and electron microscopy, to understand the involvement of cytochromes and other possible electron-mediating species in the switching between anodic and cathodic reaction modes. By switching the applied bias for a biofilm coupled to investigating the quantity and function of cytochromes, as well as the emergence of Fe-containing particles on the cell membrane, we provide evidence of a diminished role of cytochromes in cathodic EET. This work sheds light on the mechanisms of biofilm growth and suggests the possible existence of a nonheme, iron-involving EET process in cathodic mode.
微生物中外源电子传递 (EET) 在自然界中很普遍，并且已被应用于功能性生物电化学系统中。已经对 的 EET 进行了广泛的研究，并且已经发现它是通过 - 型细胞色素来促进的，这些细胞色素在阳极模式下介导电极和 之间的电荷。然而，延胡索酸盐到琥珀酸盐的阴极转化的 EET 途径仍存在争议。在这里，我们应用了多种分析方法，包括电化学、紫外-可见吸收和共振拉曼光谱、石英晶体微天平耗散、电子显微镜，以了解细胞色素和其他可能的电子介导物质在阳极和阴极反应模式之间切换中的作用。通过切换与 生物膜耦合的施加偏压来研究细胞色素的数量和功能，以及细胞膜上出现含铁颗粒，我们提供了细胞色素在阴极 EET 中作用减弱的证据。这项工作揭示了 生物膜生长的机制，并表明阴极模式下可能存在非血红素、铁参与的 EET 过程。
