Endogenous\nAntibiotics as Extracellular Electron Shuttles\nfor <i>Microbacterium</i> spp.

Electro-active microorganisms (EAMs) profoundly affect\n elemental\ngeochemical cycling and environmental remediation processes. While\nthe roles of microbial-secreted antibiotics in suppressing other coexisting\nmicrobial species have been widely recognized, here we discover that\nsuch antibiotics can also serve as redox electron mediators to augment\nmicrobial extracellular respiration. Specifically, the mitomycin C\nsecreted by <i>Microbacterium proteolyticum</i> ustc, a\nmember of <i>Actinobacteria</i>, not only inhibited the\nactivity and growth of <i>Escherichia coli</i> and <i>Bacillus subtilis</i> but also strengthened the extracellular\nelectron transfer rate by 2.5-times. This dual role of antibiotics\nrenders the <i>Actinobacteria</i> unique ecological advantages\nfor gaining energy in an anoxic environment. Overall, our work unveils\nan overlooked role of antibiotics for strengthening microbial electroactivity,\nwhich may have important implications for environmental remediation\nand bioelectrochemical applications.