Evidence of a Streamlined Extracellular Electron Transfer Pathway from Biofilm Structure, Metabolic Stratification, and Long-Range Electron Transfer Parameters
Fernanda Jiménez Otero, Grayson L. Chadwick, Matthew D. Yates, Rebecca L. Mickol, Scott Saunders, Sarah M. Glaven, Jeffrey A. Gralnick, Dianne K. Newman, Leonard M. Tender, Victoria J. Orphan, Daniel R. Bond
Abstract
Current-producing biofilms in microbial electrochemical systems could potentially sustain technologies ranging from wastewater treatment to bioproduction of electricity if the maximum current produced could be increased and current production start-up times after inoculation could be reduced. Enhancing the current output of microbial electrochemical systems has been mostly approached by engineering physical components of reactors and electrodes. Here, we show that biofilms formed by a Geobacter sulfurreducens strain producing ∼1.4× higher current than the wild type results from a combination of denser cell packing and higher anabolic activity, enabled by an increased rate of electron diffusion through the biofilms. Our results confirm that it is possible to engineer electrode-specific G. sulfurreducens strains with both faster growth on electrodes and streamlined electron transfer pathways for enhanced current production.