Endogenous Antibiotics as Extracellular Electron Shuttles for <i>Microbacterium</i> spp.

Electro-active microorganisms (EAMs) profoundly affect elemental geochemical cycling and environmental remediation processes. While the roles of microbial-secreted antibiotics in suppressing other coexisting microbial species have been widely recognized, here we discover that such antibiotics can also serve as redox electron mediators to augment microbial extracellular respiration. Specifically, the mitomycin C secreted by Microbacterium proteolyticum ustc, a member of Actinobacteria, not only inhibited the activity and growth of Escherichia coli and Bacillus subtilis but also strengthened the extracellular electron transfer rate by 2.5-times. This dual role of antibiotics renders the Actinobacteria unique ecological advantages for gaining energy in an anoxic environment. Overall, our work unveils an overlooked role of antibiotics for strengthening microbial electroactivity, which may have important implications for environmental remediation and bioelectrochemical applications.