Structural Control of Phthalate Toxicity in Agricultural Soil Biofilms: Aliphatic-Chain-Length-Driven Hazards Revealed by Field Evidence, Multiomics, and Quantum Chemical Analysis

Phthalates (PAEs) pose significant ecological risks in greenhouse soils because of their hydrophobicity and persistence. This study combined field survey, microcosm experiments, multiomics analysis profiling, and quantum chemical calculations to investigate how the aliphatic chain length influences the toxicity of PAEs toward soil biofilms. Results showed that longer-chain PAEs caused stronger inhibition of biofilm formation, reduced extracellular polymeric substance polysaccharide production, enhanced oxidative stress, and disrupted microbial community structure. Multiomics revealed that PAEs primarily affected energy metabolism, electron transport, and glycerophospholipid metabolism. Molecular docking and density functional theory (DFT) calculations further suggested that PAEs preferentially interact with the Trp198 region of NADH dehydrogenase I, with the binding strength increasing with the aliphatic chain length. This study establishes a structural toxicology framework linking the molecular structure to biofilm dysfunction, providing mechanistic insights into the ecological risk assessment of PAEs.