Electrochemical analysis of Shewanella oneidensis engineered to bind gold electrodes.

Abstract

Three-electrode bioreactors can be utilized to examine the mechanisms involved in electron flow from bacteria to insoluble electron acceptors and allow these processes to be analyzed quantitatively. As an electrode, gold is an ideal surface to study the electrophysiology occurring during extracellular respiration; yet previous research has shown that Shewanella is resistant to colonization on gold surfaces. Therefore, the goal of this work was to direct adhesion of Shewanella oneidensis to gold surfaces via cell surface display of a modified E. coli outer membrane protein, LamB, and a gold-binding peptide (5rGBP) to encourage microbe-electrode interaction, improve whole-cell biocatalytic systems, and increase overall current production. Expression of LamB-5rGBP increased the affinity of Shewanella for gold surfaces, but also led to the displacement of certain outer membrane components required for extracellular electron transport. Displacement of these outer membrane proteins decreased the rate at which Shewanella was able to reduce both insoluble iron and riboflavin. Expression of LamB-5rGBP, although effectively increasing attachment to gold, did not greatly increase current production in gold-electrode bioreactors.