The urgent need to mitigate global energy and environmental crises underscores the importance of developing clean and sustainable energy technologies. Microbial electrochemical systems (MESs) have emerged as a promising platform, exploiting the ability of electroactive microorganisms to exchange electrons with electrodes through extracellular electron transfer (EET). While conventional studies have primarily focused on community-level processes, they often overlook the intrinsic heterogeneity and dynamic behaviors of individual cells that ultimately govern MES performance. To overcome these limitations, single-cell analytical approaches are being developed, though their application to EET studies remains in its infancy. This review provides a comprehensive summary of current single-cell microbial electrochemistry studying techniques, beginning with the fundamental mechanisms of EET and progressing to electrochemical microelectrode methods and optical imaging strategies. Particular attention is given to both label-free and probe-labeled imaging approaches, each offering distinct advantages. Finally, we briefly discuss the interplay between EET and microbial behaviors at single-cell scale. These insights highlight emerging methodologies for probing single-cell EET, their applications in uncovering microbial physiology and behaviors, and the future opportunities they open for advancing microbial electrochemistry and the rational design of MESs.
Xing et al. (Fri,) studied this question.