Environmental selection shapes the ecological cascade of biofilm assembly and functional gene abundance in sandstone weathering.

Microorganisms are pivotal agents in the process of sandstone weathering; nevertheless, the ecological mechanisms that govern their transition from mere colonization to sustained weathering activity remain ambiguous. This study systematically elucidated microbe-mediated weathering mechanisms through amplicon and metagenomic sequencing of bacteria, fungi, and archaea across a sandstone weathering sequence-from original unweathered sandstone (OS), biofilm-covered sandstone (BS), to weathered sandstone (WS). The findings indicate that microbial communities undergo associations across a weathering gradient, with biofilms constituting a unique transitional state. Community assembly mechanisms undergo a transition from stochastic processes in original sandstone to deterministic processes during the processes of biofilm formation and weathering. Biofilm communities formed modular, tightly interconnected putative association networks enriched with keystone taxa. Metagenomic analysis revealed significant enrichment of functional pathways related to iron acquisition, organic acid metabolism, and sulfur cycling during weathering, with functional annotation directly linking these traits to pivotal microbial groups. The findings of this study, as suggested by partial least squares path modeling (PLS-PM), indicate that environmental changes are associated with deterministic processes and with increased microbial richness. These factors are further linked to the composition of putative keystone taxa along the weathering gradient. These pivotal groups subsequently influence the abundance of weathering-related functional genes, directly accelerating weathering processes. This finding unveils a distinct ecological cascade pathway, commencing with environmental selection and culminating in the enrichment of functional gene potentials. The present study proposes a universal framework demonstrating that sandstone weathering is associated with deterministic processes, putative keystone taxa, and synergistic gene networks. This mechanism is not only applicable to sandstone systems, but also offers novel insights into the understanding of microbially mediated mineral weathering in terrestrial environments. This process is fundamental in influencing global biogeochemical cycles, soil formation, and the preservation of geological and cultural heritage.