Uranium-induced differentiation in metabolic responses and functional potential of nitrogen-cycling microorganisms...

Uranium (U) contamination poses a severe ecological risk by disrupting key biogenic element cycles, particularly nitrogen (N) transformation. However, the extent to which intrinsic soil heterogeneity shapes the functional adaptation of N cycling microorganisms to U stress remains poorly understood. This study investigated soil microcosms with metagenomic analysis to unravel the structural and functional differentiation of N cycling communities across forest (FT), grassland (GL), and farmland (FL) soils. Our results indicated that U contamination exerted significant selective pressure, leading to distinct functional differentiation in N cycling processes (R² = 0.56) which was primarily shaped by land-use legacy (R² = 0.62). Driven by this U-induced pressure, the three soils diverged into unique N cycling adaptive strategies. Specifically, U stress shifted the FT towards a strategy of energetic autonomy, enriching robust nitrate reduction coupled with a metabolic repertoire associated with U(VI) resistance and transformation potential. In the GL, U exposure shaped a complex, self-sustaining co-occurrence network associated with potential functional stability, characterized by cross-pathway complementation among N fixation, nitrification, and anammox. Conversely, U contamination drove the FL into a maladaptive simplification, where the reduction of functional redundancy and the dominance of a single nitrification pathway led to heightened vulnerability. Collectively, this study demonstrates that U stress acts as a selective filter that amplifies pre-existing soil driven discrepancies, driving soil microbial communities onto distinct functional potential trajectories. These findings emphasize the necessity of developing differentiated risk management strategies based on the specific N cycling resilience of various soil types.