Inhibition Effect Of Antibiotics Research Articles

Promote or inhibit? Transcriptomic and metabonomic insights into the effects of antibiotics on nitrogen uptake and metabolism in Myriophyllum aquaticum

Phytoremediation is an effective nitrogen removal method to alleviate eutrophication. However, the coexistence of antibiotics may inhibit nitrogen removal by aquatic macrophytes, and the underlying mechanisms remain unclear. Here, we systematically investigated the effects of three antibiotics (norfloxacin, NOR; sulfamethoxazole, SMX; and oxytetracycline, OTC) at environmental concentrations (1 μg/L and 1 mg/L) on ammonia (NH4+–N) and nitrate (NO3-–N) removal by the aquatic macrophyte Myriophyllum aquaticum. NOR, SMX, and OTC reduced NH4+–N removal by M. aquaticum by 10–36 %, with low levels (1 μg/L) of NOR reducing NO3-–N removal by up to 60 %. Antibiotics substantially reduced the biomass and chlorophyll contents but increased the antioxidant enzymes in M. aquaticum. While antibiotics inhibited NH4+–N removal, the promotion or inhibition effect of antibiotics on NO3-–N removal by M. aquaticum depended on types and levels of antibiotics. Transcriptomic and metabonomic profile analyses revealed differentially expressed genes and metabolites, suggesting that the mechanisms underlying the promotional/inhibitory effects of antibiotics on nitrogen uptake and metabolism were related to ammonia metabolism, the tricarboxylic acid cycle, photosynthesis, and oxidative stress. Myriophyllum aquaticum exhibited better NH4+–N removal than NO3-–N removal, as NH4+–N can be directly taken up by M. aquaticum and transformed into ammonium, while NO3-–N must be absorbed by the plant and then reduced to ammonium. During this process, antibiotics disrupt genes associated with nitrogen uptake and metabolism. In this study, we provide multiomics insights into the mechanisms of nitrogen metabolism in aquatic macrophytes affected by antibiotics and offers a scientific basis for water pollution control.

Tetracycline and sulfamethazine alter dissimilatory nitrate reduction processes and increase N2O release in rice fields

Effects of antibiotics on the transformation of nitrate and the associated N2O release in paddy fields are obscure. Using soil slurry experiments combined with 15N tracer techniques, the influence of tetracycline and sulfamethazine (applied alone and in combination) on the denitrification, anaerobic ammonium oxidation (anammox), dissimilatory nitrate reduction to ammonium (DNRA) and N2O release rates in the paddy soil were investigated, while genes related to nitrate reduction and antibiotic resistance were quantified to explore the microbial mechanisms behind the antibiotics’ effects. The potential rates of denitrification, anammox, and DNRA were significantly (p < 0.05) reduced, which were mainly attributed to the inhibitory effects of the antibiotics on nitrate-reducing microbes. However, the N2O release rates were significantly (p < 0.05) stimulated by the antibiotic treatments (0.6–6000 μg kg−1 soil dry weight), which were caused by the different inhibition effects of antibiotics on N2O production and N2O reduction as suggest by the changes in abundance of nirS (nitrite reduction step) and nosZ (N2O reduction to N2 step) genes. Antibiotic resistance gene (tetA, tetG, sulI, and sulIII) abundances were significantly (p < 0.05) increased under high antibiotic exposure concentrations (>600 μg kg−1 soil dry weight). Our results suggest that the widespread occurrence of antibiotics in paddy soils may pose significant eco-environmental risks (nitrate accumulation and greenhouse effects) by altering nitrate transformation processes.