Membrane Separated Flow Cell for Parallelized Electrochemical Impedance Spectroscopy and Confocal Laser Scanning Microscopy to Characterize Electro-Active Microorganisms
By St
Published in Electrochimica Acta
2016
Abstract
Abstract Understanding the attachment of electro-active bacteria to electrode surfaces and their subsequent biofilm formation is one of the major challenges for the establishment of bacterial bioelectrochemial systems (BES). For a constant observation of biofilm growth, providing information on different stages of biofilm formation, continuous monitoring methods are required. In this paper a combination of two powerful analytical methods, Electrochemical Impedance Spectroscopy (EIS) and Confocal Laser Scanning Microscopy (CLSM), for biofilm monitoring is presented. A custom-built flow cell with a transparent indium tin oxide working electrode (WE) was constructed allowing monitoring of cell attachment to a working electrode simultaneously by {EIS} and CLSM. Cyclic Voltammetry (CV) and {EIS} of an iron (II)/iron (III) redox couple indicate that the flow cell is suitable for electrochemical experiments. An engineered Shewanella oneidensis MR-1 (ATCC700550) producing eGFP was used as electro-active model organism to demonstrate the practical application of the flow cell as {BES} to monitor cell attachment simultaneously with {EIS} and CLSM. Applying the flow cell as {MFC} (transparent working electrode poised as anode) produced a typical current curve for such a system. From the equivalent circuit used to interpret {EIS} data the charge transfer resistance {RCT} is sensitive to attachment of microorganisms. Fitted {RCT} was increased initially after cell inoculation and then lowered constantly with progressing experimental time. In parallel taken {CLSM} images show that bacteria already adhered to the {WE} 5 min after inoculation. A mono- respectively bilayer of electro-active cells was observed after 17 h on the {WE} surface. With the presented flow cell interpretation of {EIS} measurements is significantly improved by simultaneous {CLSM} imaging, leading to a wide range of attachment information and pointing to the investigation of less studied and less established electro-active bacteria.