Electrochemical characterization of direct electron uptake in electrical microbially influenced corrosion of iron by the lithoautotrophic \SRB\ Desulfopila corrodens strain \IS4\

By Pascal F. Beese-Vasbender and Simantini Nayak and Andreas Erbe and Martin Stratmann and Karl J.J. Mayrhofer
Published in Electrochimica Acta NULL 2015

Abstract

Corrosion of iron infrastructure in anoxic environments is commonly ascribed to the metabolic activity of sulfate-reducing bacteria (SRB), which can influence electrochemical processes on the metallic surface. The present study characterizes electron transfer processes at the electrode/microorganism interface of the specialized lithoautotrophic \SRB\ Desulfopila corrodens strain \IS4\ that is capable of taking up electrons directly from elemental iron, thereby leading to severe corrosion. Electrochemical analysis of the highly corrosive \SRB\ is performed in bio-electrochemical cells operated with artificial seawater under anoxic conditions, complemented by infrared spectroelectrochemical analysis and environmental \SEM\ observations. In order to provide clear insights into electron transfer processes, sterile controls and a non-corrosive hydrogenotrophic control strain are analyzed in parallel. Remarkably, the electron uptake from electrodes by D. corrodens strain \IS4\ is not restricted to iron serving as the sole electron donor for the microbial metabolism, but instead proceeds also on graphite and doped germanium cathodes. Consequently, a well-defined electrochemical analysis of the electron uptake mechanism is possible, since corrosion precipitates typically observed on iron electrodes are absent on both of the other cathode materials. Direct electron transfer in the absence of artificial electron mediators is achieved at a potential of ?0.4 V vs. \SHE\ under neutral conditions. Electrochemical and infrared spectroelectrochemical analysis indicated c-type cytochromes as the redox active components associated with the outer membrane to be involved in the direct electron uptake from reduced surfaces by D. corrodens strain IS4.

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