Thickness and roughness of transparent gold-palladium anodes have no impact on growth kinetics and yield coefficients of early-stage Geobacter sulfurreducens biofilms

Geobacter sulfurreducens is the model organism for electroactive microorganisms performing direct extracellular electron transfer and forming thick mature biofilm electrodes. Although numerous physiological properties of mature biofilm electrodes are deciphered, there is an extensive gap of knowledge on the early-stage biofilm formation. We have shown recently that transparent gold-palladium (AuPd) electrodes allow for analysis of early-stage biofilm formation using confocal laser scanning microscopy. Here we analysed the influence of thickness (ranging from 12.5 to 200 nm) and roughness of AuPd electrodes on physiological parameters of G. sulfurreducens early-stage biofilms. We show that when grown potentiostatically at -200 mV vs. Ag/ AgCl sat. KCl neither maximum current density (j(max) of similar to 80-150 mu A cm(-2)) nor lag time (lag t of similar to 0.2-0.4 days) or single cell yield coefficients (Y-Ne of 1.43 x 10(12) cells mol(e-)(-1)) of the biofilms are influenced by the electrode preparation. This confirms the robustness of the experimental approach, which is an inevitable prerequisite for obtaining reliable results in follow-up experiments. (C) 2021 Elsevier B.V. All rights reserved.