Extracellular electron transfer involving microbes is important as it closely reflects the ability of cells to communicate with the environment. However, there are few reports on electron transfer mechanisms of pure microalgae and a lack of any model alga to study the transfer processes. In the present study, nine green microalgae species were isolated from wastewater and characterized in terms of their ability to transfer electrons between cells and an electrode. One species showed direct electron transfer via membrane-associated proteins and indirect electron transfer via secreted oxygen. The microalga was identified as Desmodesmus sp. based on phylogenetic analysis and electron microscopy. Electrochemical tests demonstrated that Desmodesmus sp. was able to act as a cathodic microorganism. Stable current densities of −0.24, 35.54 and 170 mA m−2 were achieved at potentials of +0.2, −0.2 and −0.4 V, respectively, under illumination. Dissolved oxygen concentration measurement showed gradients within the microalgae biofilm: 18.3 mg L−1 in light decreasing to 4.29 mg L−1 in the dark. This study diversified the exoelectrogen library and provided a potential model microalga to explore the associated mechanism of extracellular electron transfer.
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机译：涉及微生物的细胞外电子转移非常重要，因为它密切反映了细胞与环境交流的能力。然而，关于纯微藻类的电子转移机理的报道很少，并且缺乏任何模型藻类来研究转移过程。在本研究中，从废水中分离出9种绿色微藻物种，并根据它们在细胞和电极之间转移电子的能力进行了表征。一种物种通过膜相关蛋白表现出直接电子转移，并通过分泌的氧气表现出间接电子转移。微藻被鉴定为Desmodesmus sp。基于系统发育分析和电子显微镜。电化学测试表明，Desmodesmus sp。能够充当阴极微生物。在照明下，分别在+ 0.2，-0.2和-0.4 V的电势下，可实现-0.24、35.54和170 mA m -2 的稳定电流密度。溶解氧浓度测量显示微藻生物膜内的梯度：在光照下为18.3 mg L -1 ，在黑暗中降至4.29 mg L -1 。这项研究使外生电子库多样化，并提供了一种潜在的模型微藻，以探索细胞外电子转移的相关机制。
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