Genetic technology to improve biofilms electroactivity for bioremediation applications

Hexavalent chromium bioremediation occurs through its reduction to Cr(III) and its following precipitation. Geobacter metallireducens is a dissimilatory metal reducing bacteria known to reduce Cr(VI) to Cr(III) through extracellular electron transfer. However, the effectiveness of this bioreduction process is limited by the low toxicity resistance of G. metallireducens to Cr(VI). G. metallireducens mutants with improved Cr(VI) toxicity resistance can be obtained by genome shuffling method. Here we present the experimental setup for genome shuffling of G. metallireducens, including the optimization of mutagenesis procedure and the respiration rate measure for G. metallireducens in potentiostat-controlled electrochemical cells (EC). Preliminary results show that genome shuffling of G. metallireducens is possible only in liquid growth medium. Chronoamperometry and Cyclic Voltammetry of G. metallireducens biofilms show that the biofilm increase in thickness and activity following the removal of soluble Fe(III)-citrate from the growth medium. The respiration rate of G. metallireducens biofilm was measured at stable current production. Results show that microbial biofilm voltammetry permit comparison of the best G. metallireducens mutants obtained after each round of genome shuffling.