Electrochemical Activity Produced from Abundant Expression of C‐Type Cytochromes in a Filamentous Gram‐Positive Bacterium

Abstract

Natural microbes employing c-type cytochromes (c-Cyts) for extracellular electron transport (EET) were greatly valuable to develop redox-based bioelectrochemical applications. However, low levels of c-Cyt expression limited the phylogenetically diverse Gram-positive species to be used in bioelectrochemical devices. This work reported the remarkable finding that a high level of c-Cyts was expressed in the cells of the Gram-positive strain Lysinibacillus varians GY32. c-Cyts in Lysinibacillus varians GY32 cells were expressed at a level close to those in Shewanella oneidensis. These c-Cyts were found to cluster in cytoplasmic membrane and periplasmic space, along the length of Lysinibacillus varians GY32 cell. With voltammetry and spectroelectrochemical titration, phenazine methosulfate-mediated electron transfer between the c-Cyts and an electrode was proved. These results expanded the accessible natural models of EET and suggested a new microbial platform for developing bioelectrochemical applications.

Cysteine-Mediated Extracellular Electron Transfer of Lysinibacillus varians GY32

“…Assuming the redox potential of the cysteine/cystine couple in the anodic culture was −40 mV, it would be thermodynamically favorable to deliver electrons from many redox proteins or coenzymes to the anode ( 41 ). Our recent results showed that the membrane-bound c -type cytochromes of GY32 have a midpotential of −178 mV ( 43 ). Therefore, the cysteine/cystine couple may be reduced by these c -type cytochromes in strain GY32.…”