Bidirectional extracellular electron transfer (EET) is mediated by back and forth electron delivery between microorganisms and extracellular substances. This enables the exchange of biochemical information and energy with the surrounding environments. As a novel bioenergy strategy, bidirectional EET provides low-cost opportunities for the production of clean energy sources and carriers (e.g., hydrogen and methane) as well as the production of value-added chemicals from carbon dioxide. Electrochemically active bacteria (EAB) can also transform pollutants to less toxic or benign substances in contaminated environments, and therefore they have been widely applied in bioremediation studies. Among all the available EAB, Geobacter and Shewanella are well-known for their versatility to accept/donate electrons from/to external environments. In this review, we focus on how these model EAB generate or harvest energy through bidirectional EET, as well as recent advances in the application of EET in bioelectrochemical technology and environmental bioremediation. Finally, the challenges, perspectives and new directions in the bidirectional EET studies are discussed.

双向细胞外电子转移（EET）由微生物与细胞外物质之间的来回电子传递介导。这使得能够与周围环境交换生化信息和能量。作为一种新颖的生物能源策略，双向EET为生产清洁能源和载体（例如，氢气和甲烷）以及从二氧化碳生产增值化学品提供了低成本机会。电化学活性细菌（EAB）还可在污染的环境中将污染物转化为毒性较小或良性的物质，因此它们已被广泛应用于生物修复研究中。在所有可用的EAB中，Geobacter和Shewanella众所周知，它们具有从/向外部环境接受/捐赠电子的多功能性。在这篇综述中，我们重点介绍这些模型EAB如何通过双向EET产生或收集能量，以及EET在生物电化学技术和环境生物修复中的最新应用。最后，讨论了双向EET研究中的挑战，观点和新方向。