Spectroscopic slicing to reveal internal redox gradients in electricity-producing biofilms

Exocellular electron conduction is one of the most fascinating  discoveries of microbiology in the last decade. In natural and  man-made environments it is thought to play a fundamental  role, allowing the exchange of electrons between bacterial  cells and between these and external electronic acceptors.  Moreover, it is one of the fundamental processes behind the  production of electricity by electroactive biofilms grown on  electrodes, which are of paramount importance in such  emerging technologies as microbial fuel cells,microbial  electrolysis cells, the microbial electrosynthesis process, and whole cell biosensors. Electroactive biofilms grown on polarized electrodes are  in fact a very appropriate system for exploring electron  conduction because researchers have learnt to grow them in  fully controlled conditions with excellent reproducibility.  In the typical case, biofilms of Geobacter sulfurreducens, the  most efficient current producer described to date, are grown  on a polarized electrode during 4-6 days until obtaining  a constant current. During this time, cells reproduce actively  at maximal rate, using the electrode as the electron acceptor,  until reaching a thickness of about 40-60m m. At this stage,  cells within the entire population seem to operate at an  uniform rate, as evidenced by the constant increase in the  accumulation of proteins. A remarkable feature in these  biofilms is that a uniform distribution of cell activity can only  be possible if cells at a distance from the electrode are  electrically connected to it by a low-resistance pathway that  prevents electron acceptor limitations. There is debate as to  whether such electron conduction is based on one of two  alternative mechanisms : metallic-like conduction through  nanowires, or electron hopping (superexchange) through  cytochromes.Fil: Robuschi, Luciana. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Tomba, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Schrott, Germán David. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Bonanni, P. Sebastian. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Desimone, Paula Mariela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; ArgentinaFil: Busalmen, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Mar del Plata. Instituto de Investigación En Ciencia y Tecnología de Materiales (i); Argentina. Universidad Nacional de Mar del Plata. Facultad de Ingeniería; Argentin