Effects of decabromodiphenyl ethane (DBDPE) exposure on soil microbial community: Nitrogen cycle, microbial defense and repair and antibiotic resistance genes transfer.

DBDPE, a widely used brominated flame retardant, is frequently detected in soil. However, the toxic effects of DBDPE on soil microbial communities remain unclear. This study investigated the effects of DBDPE on the microbial community shifts, the nitrogen cycle, microbial defense and repair, and antibiotic resistance genes (ARGs) transfer. After 28 days of DBDPE exposure, the soil microbial community was altered. Denitrifier were enriched by 4.07-78.22% under DBDPE exposure concentrations of 100-1000 ng/g. Additionally, the abundances of genes encoding enzymes involved in nitrification and denitrification processes were up-regulated at 100 ng/g DBDPE exposure, and further promoted at 1000 ng/g DBDPE exposure. Meanwhile, DBDPE exposure at concentrations of 100-1000 ng/g stimulated the production of extracellular polymers substances (EPS) (2155-2347 mg/kg), increased the accumulation of reactive oxygen species (ROS) (by 97.95-108.38%), and activated the antioxidant defense system of soil microorganisms, which correspondingly down-regulated catalase (CAT) genes (by 4.65-4.91%), while up-regulated superoxide dismutase (SOD) (by 0.52-2.63%) and glutathione (GSH) genes (by 19.03%-44.61%). Genes related to the tricarboxylic acid (TCA) cycle, glycerophospholipid metabolism, and peptidoglycan biosynthesis were up-regulated, enhancing cell membrane repair in response to DBDPE exposure. Moreover, the increase in DBDPE concentration selectively enriched and promoted the transmission of ARGs. The co-occurrence network of ARGs and mobile genetic elements (MGEs) revealed that DBDPE facilitated the horizontal gene transfer (HGT)-mediated transmission of transposase, ist, and insertion sequence-associated ARGs.