Bacterial Translational Motion on the Electrode Surface under Anodic Electric Field

Application of an electric field (alternating or cathodic polarization) has been suggested as a possible mean of controlling biofilm development. Bacteria on an anodically polarized surface were shown to be active and highly motile when compared with a nonpolarized condition, but no quantitative information on bacterial motion has been reported. This study investigated the effects of environmental conditions (current density and ionic strength) on the translational motion of P. aeruginosa PAO1 cells under an anodic electric field using a quantitative tracking method. Bacterial displacement for 10 s was found to be approximately 1.2 μm, irrespective of wide-ranging current densities (7.5–30 μA/cm2). However, the local dynamics of bacterial communities differed under varied current densities. The distribution of bacterial displacement appeared to exhibit a more oscillating (subdiffusive) at high current density. At the same time, the number of bacteria with a circular trajectory (superdiffusive) decreased. Bacterial movement decreased with increased ionic strength of the media, because of strong electrostatic interactions. The motion of bacterial communities on an anodically polarized surface under various conditions is discussed, along with possible mechanisms. In addition, the control of biofilm growth was partly demonstrated by changing the motility of bacterial cells under anodic polarization.