Beyond rapid degradation: The underestimated ecological risk of sodium dehydroacetate on soil microbiome and gene horizontal transfer

Sodium dehydroacetate (Na-DHA) is a compound with potent antibacterial properties, leading to its widespread use in food and feed industries. However, its biocidal action exerts selective pressure that can drive resistance evolution, thereby altering microbial community structure and dynamics. Consequently, the environmental fate and potential hazards of Na-DHA residues warrant thorough investigation. This study systematically examined the adsorption and degradation dynamics of Na-DHA in soil and evaluated the ecotoxicological effects of its transformation products. Furthermore, it assessed the impact on soil microbial activity, community structure, antibiotic resistance genes (ARGs), and the abundance of key functional genes. Analysis revealed that Na-DHA underwent complete degradation in soil within 14 days, with a half-life of 1.77–3.0 days, and exhibited strong soil adsorption, reaching equilibrium rapidly within two hours. Na-DHA significantly inhibited fungal growth (50–80 %) and similarly suppressed bacterial growth (24–71 %). Metagenomic profiling showed that 30-day exposure to high Na-DHA enriched 70 % of the top 40 abundant ARGs and markedly increased the prevalence of mobile genetic elements (MGEs)-83.8 % of the top 37 MGEs were elevated. This suggests that Na-DHA stress may facilitate horizontal gene transfer, thereby promoting ARGs dissemination. Correspondingly, broad upregulation of functional genes linked to membrane permeability, ATP synthesis, and the SOS response was observed, revealing microbial adaptive mechanisms involving metabolic and structural reprogramming to mitigate Na-DHA-induced stress. • Na-DHA exhibited a soil half-life of 1.8–3.0 days conforming to pseudo-first-order kinetics. • Na-DHA in soil suppressed fungal growth by 50–80 % and bacterial growth by 24–71 %. • Na-DHA stimulated respiration initially but suppressed ammonification and nitrification. • 70 % of the top 40 ARGs were upregulated at 1000 mg/kg Na-DHA treatment. • The top 37 MGEs abundance rose to 219 % (100 mg/kg) and 275 % (1000 mg/kg) of the control.