The hidden mechanistic hand: the mechanical force that drives global biogeochemical cycles

Microbial life has traditionally been understood to be driven by phototrophic and chemotrophic energy sources. However, recent discoveries have revealed the previously overlooked potential role of ubiquitous mechanical energy to drive biogeochemical cycles. This review presents recent advances in mechanically driven biogeochemistry and proposes a novel paradigm in which the piezoelectric effect converts mechanical forces from environmental processes (e.g., river flow, tides, and seismic activity) into electrons that drive microbial metabolism. This review uniquely consolidates these dispersed insights into a coherent 'mechano-biogeochemistry' framework, explicitly distinguishing it from proximate fields like tribochemistry, and mechanochemistry by its focus on a microbially mediated, two-step energy transduction pathway (mechanical force → electron → biochemical energy). This study investigates the mechanisms by which biohybrid piezoelectric systems, composed of piezoelectric materials such as BaTiO3, ZnO, and quartz, in conjunction with electroactive microorganisms, facilitate processes including autotrophic carbon fixation, denitrification, sulfate reduction, and methanogenesis in the absence of light or conventional chemical electron donors. Elucidating this mechanism not only provides an alternative and potential theoretical basis for understanding microbial survival strategies in energy-limited environments, such as the deep biosphere, but also potentially offers new perspectives for exploring the evolution of early metabolic pathways and global element cycling patterns. By integrating principles from materials science, geophysics, and microbiology, this review proposes 'mechano-biogeochemistry' as a significant complementary framework for understanding Earth's element cycles, with profound implications for environmental engineering and sustainable bioproduction.