In situ quantification of bacterial adhesion to electrically polarized metallic surfaces under shear

Microbial biofouling causes human and economic loss through hospital acquired infections, corrosion and drag losses on ship hulls, and in both oil and food distribution. Microorganisms interacting with surfaces under these open channel flows contend with high shear rates and active transport to the surface. The metallic surfaces they interact with carry charge at various potentials, which are little addressed in the literature. We demonstrate that mass transport limiting current, chronoamperometry, and cyclic voltammetry in a rotating disk electrode are ideal for studying adhesion of microbes to electrically polarized metallic surfaces under shear. We study the adhesion of Escherichia coli, Bacillus subtilis, and 1 µm silica microspheres over a range of shear stress from 0.15 – 37.33 dynes. cm<sup>-2</sup> or shear rates of 14.73 – 3727.28 s <sup>-1</sup>. The mechanism we use has been qualitatively reported in the literature. Unlike quartz-crystal microbalance, our methodology measures changes in area instead of mass, simultaneously providing measurements of the protein binding step that initiates biofilm formation. Our deposition rates agree with those found using optical systems. However, unlike fluorescence microscopy, our methods are in situ and apply to a larger range of materials than on-chip flow devices.