Microbial Communities Powering Plant-Microbial Fuel Cells: Diversity, Functions and Biotechnological Perspectives.

The pressing challenges posed by climate change and the depletion of traditional energy sources have intensified the search for alternative energy-harvesting technologies. Plant-microbial fuel cells (PMFCs) have emerged as a promising solution. Although they are not yet energetically competitive, their potential application in low-power devices as a battery replacement has been widely explored. PMFCs operate by integrating living plants with microbial fuel cells to generate electricity in situ through the metabolic activity of electroactive microorganisms (EAMs) in the rhizosphere. These microbes degrade root exudates and play a central role in PMFC performance and long-term stability. In this review, we selected 21 studies that examined bacterial and archaeal communities in PMFCs, comparing their microbial composition and resulting electricity outputs. We highlight how differences in plant species, system configurations, and environmental conditions influence the structure and function of microbial communities. We also discuss the methods used for microbial community assessment and address the persistent lack of standardisation across studies, which limits comparability. Finally, we outline future research directions aimed at optimising PMFC performance, including the search for electroactivity biomarkers, the potential of genetic engineering and nanomaterials, and the largely unexplored electroactive potential of eukaryotes in these systems. This review advances the existing literature by incorporating recent findings and offering a renewed perspective on PMFC systems.