Potential-dependent extracellular electron transfer pathways of exoelectrogens

Exoelectrogens are distinct from other bacteria owing to their unique extracellular electron transfer (EET) abilities that allow for anaerobic respiration with various external redox-active surfaces, including electrode and metal oxides. Although the EET process is known to trigger diverse extracellular redox reactions, the reverse impact has been long overlooked. Recent evidences show that exoelectrogens can sense the potential changes of external surfaces and alter their EET strategies accordingly, which imparts them remarkable abilities in adapting to diverse and redox-variable environment. This mini-review provides a condensed overview and critical analysis about the recent discoveries on redox-dependent EET pathways of exoelectrogens, with focus on Geobacter sulfurreducens and Shewanella oneidensis. We summarize the detailed responses of various EET components, analyze the drives and mechanisms of such responses, highlight the diversity of EET dynamics among different bacterial species and under integrated effects of redox potential and surface chemistry, and discusses the future research needs.