Joey Erwin

Geobacter sulfurreducens is a soil-dwelling obligate anaerobe. Rather than use fermentation, geobacter species carry out anaerobic respiration utilizing inorganic metals, typically Fe(III) species, as terminal electron acceptors. Geobacter uses multiheme cytochromes in its metal reducing metabolism to both transport electrons across the outer membrane and to increase the cell's surface area via the secretion of cell-attatched cytochrome polymers known as nanowires, which allow geobacter to access metals that are microns away from the cell. These cytochrome polymers also enable geobacter to grow in hundred-micron thick biofilms on electrodes, allowing the cells on the outside of the biofilm to interact with the electrode and use it as a terminal electron acceptor.

My research has focused on four of the key cytochromes complexes used by geobacter: two involved in Fe(III) metabolism, Om(abc)B and OmcS, and two involved in biofilm formation, ExtA and OmcZ. Over the course of my PhD, I have developed methods to purify all of these cytochromes from the native geobacter host. I have focused on characterizing the biochemical, catalytic, and electrochemical properties of these proteins, as well as their interactions with their potential metabolic interaction partners. I have also studied the assembly mechanisms of the cytochrome nanowires OmcS and OmcZ using a mix of genetic and biochemical techniques.