2020 Volume 88 Issue 3 Pages 224-229
Microbial extracellular electron transfer (EET) in diverse environments has gained increasing attention. However, the EET capability of oral pathogens and associated mechanisms has been scarcely studied. Here, our results suggest that the Capnocytophaga ochracea, an etiological human pathogen showed current production and demonstrated a rate enhancement of electron transport at a high cell-density. C. ochracea produced ∼10-fold more current at an OD600 of 0.5 associated with twice a higher glucose consumption rate per cell, compared to 0.1, measured in a three-electrode electrochemical system by single-potential amperometry at +0.2 V (vs Ag/AgCl [sat. KCl]). During current production, the accumulation of the redox molecules on the electrode was observed at high OD600 compared to low OD600. Apart from cell released redox active product, externally added redox active additives enhanced the electron transport, suggesting the EET capability of C. ochracea via electron mediator. A higher metabolic activity via single-cell assay (based on anabolic incorporation of 15NH4+) in cells that did not attach to the electrode strongly suggests the EET rate enhancement through an electron mediator. As bacterial populations play a role in the pathogenesis of human infections such as periodontitis, our results suggest that population-induced EET mechanisms may facilitate in-vivo colonization of C. ochracea.
