Electron transfer in Gram-positive bacteria: enhancement strategies for bioelectrochemical applications

To this day, bioelectrochemical systems are still perceived as one of the rising technologies due to their versatile applications in electricity production, bioremediation, biosensors, and production of value-added products. While the majority of bioelectrochemical applications utilize Gram-negative bacteria, Gram-positive bacteria has not received sufficient attention. The lack of adequate knowledge about their electron transfer pathways along with the presence of a thick non-conductive cell wall are among the reasons behind their limited use. In this review, the electroactivity of Gram-positive bacteria will be covered describing the different pathways of electron transfer among different electroactive Gram-positive strains. Special emphasis will be given to the role of multiheme cytochromes, quorum sensing molecules, peptide-based signalling, and pili in the extracellular electron transfer. This review will also provide an overview of possible approaches for enhancement strategies of electron transfer such as enhancing biofilm formation, biocomposites and cell perforation. Understanding the fundamentals is critical for improving the use of Gram-positive bacteria in bioelectrochemical systems and may lead to the discovery of new applications.