Piezophilic activity dominates the Puerto Rico Trench deep subseafloor biosphere

Abstract

Hydrostatic pressure defines the deep ocean, yet its role in structuring microbial activity across the subseafloor biosphere remains poorly understood. Here, we assessed pressure effects on anabolic activity in sediment communities across margin-proximal, bathyal, abyssal, and hadal settings of the Puerto Rico Trench (493-8,385 m water depth). Community-level responses to pressure reversed with burial, revealing an unrecognized shift toward piezophily in communities down to 20 meters below seafloor (mbsf). Atmospheric pressure yielded higher proportions of active cells in surficial sediments, whereas in situ pressure yielded higher proportions in the subseafloor. Pressure also structured active-community composition; in trench-axis sediments down to 8.35 mbsf, JS1/Atribacterota populations within widespread hadal lineages exhibited a physiological response to in situ pressure, indicative of subseafloor piezophily. These findings suggest that hydrostatic pressure acts as an ecological filter after burial, favoring piezophilic traits that may support microbial persistence in the deep subseafloor biosphere.