Impacts of Naphthenic Acids (NAs) Exposure on Soil Bacterial Community and Antibiotic Resistance Genes (ARGs) Dissemination.

Naphthenic acids (NAs) are indigenous and complex components in petroleum. In the context of increasing global energy demand, the increasing extraction of fossil resources leads to increased environmental release of NAs, resulting in various environmental risks. However, the impact of NAs exposure on soil microorganisms remains still unclear. This study constructed a microcosm system to explore bacterial community structure and function, biological risk generation, and the mechanism of antibiotic resistance genes (ARGs) dissemination under NAs exposure. After 28 days of NAs stimulation, the denitrifying bacteria were enriched and the abundance of genes related to nitrogen cycle was up-regulated, enhancing nitrification and denitrification. Meanwhile, NAs stimulated the production of extracellular polymeric substances (EPS) and the accumulation of reactive oxygen species (ROS), as well as activated the glutathione antioxidant system. Furthermore, the cell metabolic, repair, and transfer regulatory pathways were enhanced under NAs exposure. The networks of ARGs with genera and mobile genetic elements (MGEs) indicated that NAs exposure promoted the enrichment of ARGs in hosts, the selective accumulation of MGEs, and the induction of horizontal gene transfer (HGT) of ARGs. This study will provide valuable perspectives of interactions between NAs and its microecological environment, as well as ARGs transfer mechanisms.