Clostridium isatidis colonised carbon electrodes: voltammetric evidence for direct solid state redox processes

Bacteria are known to interact with their environment via oxidation and reduction processes driving or driven by their metabolism. These bacteriological processes are important in areas of corrosion, mining and waste treatment. However, molecular level details on how electrons are transferred between the cell and a solid reactant are not well known. In this study in situ electrochemical interrogation of redox processes in living bacteria probed with a graphite electrode yields unique mechanistic information on the reduction of solid indigo by the moderately thermophilic bacterium Clostridium isatidis. This reduction process yields the reduced form, leuco-indigo, which is an important intermediate in the dyeing industry. The process is shown to be a `true' solid state process rather than involving solubilisation of indigo. This finding has important implications for the application of bacterial-driven reduction in indigo dyeing.