Exploration of bifurcated electron transfer mechanism in Bacillus cereus for enhanced power generation in double-chambered microbial fuel cells

Abstract

Extracellular Electron Transfer (EET) is considered as the communication bridge between bacterial cells and outer electron acceptors. Apart from a few model microorganisms conventionally studied, the literature regarding the EET mechanism in Gram-positive bacteria and its conductive interaction is sparse. In the present study, proteolytic Gram-positive bacteria - Bacillus cereus is explored for enhancement of power generation in Microbial Fuel Cells (MFC). A low zeta potential (−0.1 V) of B. cereus, enables it to release electrons and protons much faster. We achieve a power density as high as 400 mW m−2 with a current density of ~5.8 mA cm−2 by inoculating an MFC with B. cereus. A genome wide transcriptome analysis by RNA-seq is used to categorize the genes and the significant pathways potentially involved in EET in B. cereus. The expression of gene cluster encodes for PTS (Phosphotransferase system) that catalyzes and transport phosphorylation of disaccharide present in the medium. This plays a regulatory role in biofilm formation. Simultaneously the secretion and assembly of extracellular flavin molecules by B. cereus, shuttle and mediate electron to the extracellular acceptor. In short, B. cereus uses bifurcated pathway i.e., directly by aligning the cytochrome complex and indirectly by secreting flavins molecules to promote electron transfer. These findings reveal its significant functional role in MFCs’ electrode community for sustainable bioenergy production.