DDT exposure drives time-dependent restructuring of soil microbiomes in urban garden microcosms

Dichlorodiphenyltrichloroethane (DDT) remains a pervasive legacy contaminant in urban soil matrices, yet the temporal dynamics of how it reshapes microbial community assembly remain poorly characterized. In this study, we investigated the successional response of an urban garden soil microbiome (Istanbul, Türkiye) to DDT exposure using a laboratory-scale microcosm framework. Soil samples were collected across a 15-day gradient (Days 0, 5, 10, and 15) and analyzed via 16S rRNA gene amplicon sequencing. DDT exposure was associated with time-dependent shifts in microbial diversity and community structure. Rather than showing evidence of broad diversity loss, Shannon diversity increased steadily in treated soils, suggesting niche expansion following the suppression of sensitive taxa. Differential abundance analysis identified a responder consortium; genera such as Rhodococcus, Kribbella, Nitrospira, Solirubacter, and Millisia significantly increased, whereas Pedomicrobium, Lysobacter, Pseudoarthrobacter, and Sedimentibacter declined. Inferred functional profiling revealed a marked metabolic restructuring in which pathways involved in aromatic amino acid and fatty acid metabolism decreased, while modules related to the degradation of chlorinated aromatic compounds, redox homeostasis, and stress responses were enriched. These findings suggest that DDT induces a specialized successional trajectory in soil microbiome, reflecting an adaptive transition toward a stress-resilient and potentially degradative community.