Application of external voltage-applied enhances surface adhesion of Shewanella oneidensis MR-1

Abstract

Electroactive bacteria play a crucial role in electrocatalytic oxidation and reduction reactions within bioelectrochemical systems (BES). However, the influence of BES startup modes on the adhesion of electroactive bacteria and the underlying mechanisms remains elusive. We hypothesize that startup mode-induced microniches trigger changes in bacterial motility, which mediate bacterial adhesion on anodic surface. To test this hypothesis, we employed Shewanella oneidensis MR-1 as a model strain and launched investigations in single-chambered BES under both external voltage-free (EVF) and external voltage-applied (EVA) modes. Our results showed that the EVA mode facilitated MR-1 adhesion up to fourfold compared to the EVF mode. Surface chemistry analysis revealed that EVA mode, with proper external voltages (400–600 mV), enhanced substrate adsorption onto anodic surfaces by up to 410 %, significantly promoting bacterial cell movement and chemotactic migration towards anodic surfaces, thereby facilitating bacterial adhesion. Principal component analysis and structural equation modeling indicated that lactate adsorption capacity was the determining factor for bacterial adhesion under EVF mode, whereas external voltage diminished the effect of lactate on triggering cell motility and subsequent bacterial adhesion in the EVA mode. Our findings provide valuable insights into the initiation and enhancement of electrochemically active biofilm on electrode surfaces in BES.