Single Electrochemical Impacts of Shewanella oneidensis MR-1 Bacteria for Living Cells Adsorption onto a Polarized Ultramicroelectrode Surface

Single electrochemical impacts of Shewanella oneidensis MR-1 Gram-negative electroactive bacteria onto ultramicroelectrode surfaces are reported and in-depth analysed. Chronoamperometry measurements recorded onto 10 mu m-diameter Pt and 7 mu m-diameter carbon fibre disk ultramicroelectrodes in a 20mM potassium ferrocyanide aqueous solution in the presence of living bacteria show an electrostatic attraction of Shewanella cells onto the ultramicroelectrode surface polarized at +0.8V vs Ag/AgCl. Single current step events analysis and atomic force microscopy experiments confirm the adsorption of living bacteria following the collision onto the ultramicroelectrode surface. The bacteria washing step before the chronoamperometry measurements leads to lower current step events related to the smaller size of the living cells. The electrostatic attraction of the negatively charged bacteria onto the positively charged ultramicroelectrode surface polarized at the oxidation potential of ferrocyanide is clearly demonstrated.