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

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.