Potassium channel mediates electroactive biofilm formation via recruiting planktonic Geobacter cells

Potassium (K⁺)-channel-based electrical signaling can coordinate microbial actions at a distance that provides an evolutionary advantage to cell communities. Electroactive cells are usually cultured surrounded by an electric field which provided stronger electrical signaling than the K⁺-mediated electrical signaling. Whether the K⁺ signaling also plays a role in coordinating the behavior of electroactive microorganisms has not been accurately demonstrated. Thus, we constructed a K⁺-channel-deficient strain ΔgsuK of Geobacter sulfurreducens to directly investigate roles of K⁺ signaling in electroactive biofilm formation for the first time. The ΔgsuK strain exhibited significantly inferior biofilm formation (i.e., biomass, thickness and component) and consequently showed weaker electrical performance (i.e., start-up time, current output, electrochemical catalytic behavior and charge transfer resistance) than the wild-type strain. Individual electric generation capacity and the expression of genes involved in biofilm formation and electrical performance in the single cell did not significantly change with the deletion of gsuK, indicating that K⁺ signaling indeed influenced the recruiting behavior of planktonic cell but not the functioning of the single cell related to biofilm formation or electric generation. This study is intended to provide an in-depth understanding of electroactive biofilm formation and serve as a basis for optimizing its electrical performance via strengthening the recruitment behavior.