Abstract
About fifteen years ago, the ability of certain micro-organisms to grow on the surface of an electrode, extracting electrons from organic compounds and directing them to the electrode material, was discovered. Thanks to these micro-organisms, electrons from the oxidation of a wide variety of compounds can be injected into an electrical circuit. Simply close the circuit with a conventional cathode, and you have a so-called "microbial" fuel cell. Such a cell generates electricity through the oxidation of renewable fuels, found in large quantities in domestic effluent or agricultural waste, for example. The result was a particularly attractive technology, but also the discovery of an unexpected link between microbial life and electricity.
Initial studies showed that certain bacterial cells act by connecting directly to the electrode surface, using a sophisticated redox chain to transfer electrons across their membrane. However, this mechanism requires direct contact between the bacterial cell and the electrode. It was then demonstrated that cells far from the electrode surface can also participate in electron transfer via two mechanisms. Some synthesize small extracellular molecules which they use as redox mediators. Others connect via pili, a kind of nanowire they synthesize and which possess electrical conducting properties. The electrical conduction properties of pili have been the subject of lively debate, and will be commented on. Ultimately, the diversity and effectiveness of strategies developed to ensure extracellular electronic exchanges suggest that this may be an essential function for microbial life.
The presentation will conclude with a brief review of the many technologies to which electro-microbial catalysis could give rise, in fields as varied as electricity generation, hydrogen production, effluent treatment or the synthesis of molecules of interest fromCO2.
