Are all microbes electroactive?

Abstract

Microbial electroactivity enables microorganisms to exchange electrons with extracellular electron donors and acceptors. Initially identified in Geobacter and Shewanella, it has now become evident that microbial electroactivity is prevalent in a variety of environments, facilitating access to distant and scarce electron donors and acceptors. This phenomenon is not confined to a few select microbes but spans across the three domains of life, viz. archaea, bacteria, and eukaryotes. In this perspective, we discuss electroactivity as a unifying metabolic trait across diverse microbial taxa, including phototrophs, sulfur-oxidizing bacteria, iron-oxidizing bacteria, nitrogen fixers, and even obligate aerobes. We highlight recent findings regarding possible mechanisms for the spread of electroactivity via horizontal gene transfer. Importantly, structurally conserved mechanisms of extracellular electron transfer (EET) across different microbial groups underscore its evolutionary significance. Considering the dominance of anaerobic metabolisms on early Earth, we propose that electroactivity is an ancestral adaptation available to all extant microorganisms.