6PPD-Q driven rare and abundant taxa functional partitioning shapes soil ecological response

N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine-quinone (6PPD-Q), a toxic transformation product of tire antioxidants, may pose ecological risks to soil ecosystems due to its persistence and strong adsorption. However, its degradation mechanisms and ecological impacts in soil remain poorly understood. Here, we conducted a 49-day microcosm experiment to investigate 6PPD-Q degradation dynamics and its effects on soil microbial communities, enzyme activities, metabolites, and dissolved organic matter (DOM). Degradation was time-dependent, with delayed but significant effects on nitrogen transformation and enzyme activity. Microbial community assembly shifted from stochastic to deterministic, with rare taxa dominating pollutant degradation and metabolic functions, while abundant taxa maintained energy metabolism and network stability. Metabolite-DOM co-occurrence networks indicated metabolic reprogramming under stress. High 6PPD-Q concentrations inhibited DOM humification and stable carbon pool formation. These findings highlight a rare taxa-driven and metabolite-DOM-mediated mechanism underlying microbial adaptation and carbon-nitrogen restructuring in contaminated soils, offering insights into the ecological consequences of tire-derived pollutants.