Faustino Marisa M, Fonseca Bruno M, Costa Nazua L, Lousa Diana, Louro Ricardo O, Paquete Catarina M
Instituto de Tecnologia Química e Biológica António Xavier, Universidade Nova de Lisboa, Av. da República, 2780-157 Oeiras, Portugal.
Microorganisms. 2021 Jan 31;9(2):293. doi: 10.3390/microorganisms9020293.
Bioelectrochemical systems (BES) are emerging as a suite of versatile sustainable technologies to produce electricity and added-value compounds from renewable and carbon-neutral sources using electroactive organisms. The incomplete knowledge on the molecular processes that allow electroactive organisms to exchange electrons with electrodes has prevented their real-world implementation. In this manuscript we investigate the extracellular electron transfer processes performed by the thermophilic Gram-positive bacteria belonging to the genus, which were found to produce higher levels of current and tolerate higher temperatures in BES than mesophilic Gram-negative bacteria. In our study, three multiheme -type cytochromes, Tfer_0070, Tfer_0075, and Tfer_1887, proposed to be involved in the extracellular electron transfer pathway of , were cloned and over-expressed in . Tfer_0070 (ImdcA) and Tfer_1887 (PdcA) were purified and biochemically characterized. The electrochemical characterization of these proteins supports a pathway of extracellular electron transfer via these two proteins. By contrast, Tfer_0075 (CwcA) could not be stabilized in solution, in agreement with its proposed insertion in the peptidoglycan wall. However, based on the homology with the outer-membrane cytochrome OmcS, a structural model for CwcA was developed, providing a molecular perspective into the mechanisms of electron transfer across the peptidoglycan layer in .
生物电化学系统（BES）正在成为一套多功能的可持续技术，可利用电活性生物从可再生和碳中和源生产电力及增值化合物。由于对电活性生物与电极交换电子的分子过程了解不完整，阻碍了它们在现实世界中的应用。在本论文中，我们研究了属于该属的嗜热革兰氏阳性细菌所进行的细胞外电子转移过程，发现这些细菌在生物电化学系统中比嗜温革兰氏阴性细菌能产生更高水平的电流并耐受更高温度。在我们的研究中，三种被认为参与该菌细胞外电子转移途径的多血红素型细胞色素Tfer_0070、Tfer_0075和Tfer_1887在大肠杆菌中被克隆并过表达。Tfer_0070（ImdcA）和Tfer_1887（PdcA）被纯化并进行了生化特性分析。这些蛋白质的电化学特性支持了通过这两种蛋白质进行细胞外电子转移的途径。相比之下，Tfer_0075（CwcA）在溶液中无法稳定存在，这与其被认为插入肽聚糖壁的情况相符。然而，基于与外膜细胞色素OmcS的同源性，构建了CwcA的结构模型，为该菌中肽聚糖层的电子转移机制提供了分子层面的视角。
