Extracellular Electron Transfer

Many microbes living in extreme environments have developed the ability to respire without oxygen. A phylogenetically diverse subgroup of these microbes use extracellular electron transfer (EET) to couple their metabolic pathways to external electron acceptors under anaerobic conditions. EET is a critical step in a variety of microbially-mediated phenomena ranging from geochemical cycling to power generation in electrochemical cells. In the Griguis lab, we study a variety of mechanisms by which microbes may be capable of EET, such as direct contact with electrodes and/or minerals, electron transfer mediated by soluble redox shuttles, biogenic structures such as pili or other filaments, or biofilm formation. We seek to understand how microbes carry out EET, how surface properties influence EET, and the role of EET in microbial energy metabolism in anaerobic environments. We are also interested in developing new technologies to harness microbial EET for sustainable energy production and biocatalytic processes.

Figure 1. Dense biofilms form on the electrodes of microbial fuel cells, and suggest that these organisms are capable of extracellular electron transfer. We use microbial fuel cells and other bioelectrochemical systems to study uncultivated microbes that are capable of EET, to better understand their role in natural ecosystems.

Figure 2. A chambered microbial fuel cell deployed at 950 meters water depth in the Monterey Canyon. We use such systems to study the nature and extent of EET-capable microbes in anaerobic marine sediments.