Types of energy utilization by microorganisms. (A) Phototrophy; (B) chemotrophy; (C) electrotrophy; (D) piezo-electrotrophy. While all microorganisms involve electron transfer in metabolism and can be broadly considered electroactive, this article narrowly defines electrotrophic microorganisms as those directly acquiring electrons from external sources (e.g., minerals or electrodes) to emphasize piezoelectrotrophy’s uniqueness—generating/acquiring electrical energy from mechanical forces via piezoelectric mechanisms.