Comparison of Ndh2-dependent EET to the different physicochemical properties that were hypothesized to drive activity, including LogD, ΔGcomp, E o , tPSA, and Dwater, revealed that activity correlated linearly to ΔGcomp (p = 0.0115, Fig. ) and LogD (p < 0.0001, Fig. ). The LogD analysis does omit 34 as this mediator possesses a positive ΔGcomp, thus indicating an unfavorable interaction with Ndh2. No relationship was observed between EET activity and E o , tPSA, or Dwater (Fig. ). Additionally, the E o of the top ten EET active compounds (-1.30 to -0.16 V, Table ) was not distinguishable from the range of E o in the library Therefore, a successful mediator should be relatively polar (~LogD < 2), have favorable predicted free energy of binding (< -2.5 kcal/mol). Since screening mediators via iron(III) oxide reduction is much higher throughput than BES experiments (Fig. ), we used the high throughput assay data to select compounds for further study. We selected five structurally distinct mediators for a more thorough analysis in a BES. This included three amine analogs (23, 24, and 27; Fig. ), and two hydroxyl analogs (7 and 21; Fig. ). To characterize each mediator's electrochemical properties, we conducted cyclic voltammetry (CV) at varying scan rates (Fig. ). The Dwater of each quinone was calculated from the CV data by plotting the peak current (ip) against the square root of the scan rate ( 1/2 ). According to the Randles-Sevcik equation, the resulting linear curves confirmed that the electron transfer process to the electrode is diffusion-controlled, as expected. The diffusion coefficients ranged from 1.1210 -6 to 4.3510 -7 cm 2 /s, consistent with values reported for quinone diffusion in Table . To further evaluate each quinone's potential use in biosensing applications, we performed BES experiments following previously published protocols, evaluating the current generation from each mediator in the presence of the same two L. plantarum strains previously described in triplicate independent reactor experiments (Fig. ). All five mediators enabled Ndh2-dependent EET; however, the hydroxyl analogs (7 and 21) produced limited signal above the background current generated by the Ndh2-deficient strain (Fig. ). In contrast, the amine analogs (23, 24, and 27) produced steady-state current in the Ndh2-competent strain that was significantly greater than the background signal. The background signal from the Ndh2deficient strain was very low, settling to a current density value close to 0 μA/cm 2 within 8 to 12 h (Fig. ). Moreover, the temporal evolution of current across the three analogs was qualitatively similar, reaching the peak within ~4 h and remaining near that peak level for the duration of the experiment. These data show that these amine analogs stably mediate Ndh2-dependent EET over 24 h, strongly suggesting they could effectively mediate signals for bioelectronic sensing. The difference in relative current magnitude compared to iron(II) generation for each mediator is likely due to inherent differences in their interactions with the different TEA (iron(III) oxide vs electrode).