Electrical conductivity and application of microbial nanowires

Abstract:

The extracellular respiration of microbes is the key energy metabolism in the anaerobic environment, driving the global biogeochemical cycle of some key elements, like C, N, S and Fe. The discovery of microbial nanowire is a milestone in the study of extracellular respiration, which promoted the study of electromicrobiology. Microbial nanowires are conductive filaments growing on the surface of bacteria. They transfer intracellular metabolic electrons outward for the reduction of extracellular electron acceptors promoting extracellular respiration or they transfer electrons to other microbes forming syntrophic cocultures. This process broadens the knowledge on electron transfer in organism and expands the interactions between microorganism and the natural environment. Owing to the excellent conductivity, microbial nanowires have the prospect of a broad application. Studies on the conductivity, ecological functions and the applications in biomaterials, bioenergy, bioremediation and human health of microbial nanowires have been regarded as a pioneering field and the focus of research in electromicrobiology. However, the biological and ecological functions of microbial nanowires are unknown and the mechanism of electron transfer along nanowire is ambiguous. Here, we will begin by summarizing all published microbial nanowires and their reported characteristics and functions. Two representatives of Geobacter sulfurreducnes and Shewanella oneidensis are included to introduce the composition and structure of their microbial nanowires. Furthermore, after presenting the methods and technologies used for conductivity measurement, the conductivity models of microbial nanowires (metabolic-like conductivity and electron hopping) are discussed and compared. We also suggest future studies and applications of microbial nanowires. The problems, challenges and opportunities analyses of microbial nanowire study are also provided.