Metabolism of sulfamethoxazole in Arabidopsis thaliana cells and cucumber seedlings (2023)

The extensive occurrence of antibiotics in farmland soil might threaten food safety. The bioaccumulation potential of antibiotics in edible vegetables and crops grown under realistic farming scenarios was reviewed and the human health risk was assessed. A total of 51 antibiotics were documented in 37 species of daily consumed crops. Among different classes of antibiotics, tetracyclines (TCs) exhibited higher residue levels in plants than quinolones (QNs), sulfonamides (SAs), and macrolides (MLs), with median values ranging from 5.10 to 15.4 μg/kg dry weight. The favored accumulation of TCs in plants was probably linked to their relatively higher residual concentrations in soils and greater bioconcentration factors. Compared with the plants grown in open field, accumulation of antibiotics was higher in plant grown under greenhouse condition, probably due to the higher residue levels of antibiotics in the greenhouse soil with intensive application of manure. Cocktails of antibiotics were investigated in potato, corn, carrot, tomato, lettuce, and wheat. Among them, corn exhibited relatively high median concentrations of antibiotics (0.400–203 μg/kg dry weight). Antibiotics tended to accumulate in plant root and their concentrations in fruit were generally low. Risk assessment revealed that human health risk was under the alert line through the daily consumption of antibiotic contaminated vegetables and food crops.

The application of pig slurry as fertilizer in agriculture provides nutrients, but it can also contain veterinary medicines, including antibiotic residues (ABs), which can have an ecotoxicological impact on agroecosystems. Furthermore, uptake, translocation, and accumulation of ABs in crops can mobilize them throughout the food chain. This greenhouse study aims to assess AB uptake from soil fertilized with pig slurry and its phenotypical effects on Lactuca sativa L. The plants were cropped in loamy clay soil dosed at 140kg total N/ha and containing antibiotics (lincomycin, sulfadiazine, oxytetracycline, and enrofloxacin) at different concentration levels (0, 0.05, 0.5, 5, 50, and 500mg/kg fresh weight, fw). Whereas sulfadiazine (11.8ng/g fw) was detected in lettuce leaves at the intermediate doses (0.5mg/kg), lincomycin and its transformation products (hydroxy/sulfate) were only detected at the 50mg/kg fw dose. In addition, increased AB doses in the pig slurry resulted in decreased lettuce fresh weight and lipid and carbohydrate content and became lethal to lettuce at the highest AB concentrations (500mg/kg fw). Nevertheless, even at higher doses, the AB content in lettuce following pig-slurry fertilization did not pose any direct significant human health risk (total hazard quotient<0.01). However, the promotion of antimicrobial resistance in humans due to the intake of these vegetables cannot be ruled out.

Plants play a cardinal role in removing various pollutants through the synergistic interaction with filling materials and microbes of constructed wetlands (CWs). However, the information regarding the selection of plant species to remove pharmaceutically active compounds (PhACs) is not adequate. The present study attempted to select an appropriate plant species for CWs, considering their characteristics and physiological response to PhACs. In this regard, batch hydroponics studies were carried out to assess the removal, fate, and antioxidative response of carbamazepine (CBZ) in four wetland plant species (Canna indica, Colocasia esculenta, Phragmites australis, and Chrysopogon zizanioides). The specific uptake potential of CBZ (in terms of plant dry biomass) was found to be in the order: C. indica (14.48 mg/g) > P. australis (11.71 mg/g) > C. esculenta (8.67 mg/g) > C. zizanioides (6.04 mg/g). The results showed that exposure to CBZ (0–30 days) caused an accumulation of reactive oxygen species (ROS) in the plant tissues, causing a decline in chlorophyll content, root activity, and increased oxidative stress. However, the selected plants could recover from the oxidative damages to a certain extent in the recuperation phase (31–60 days). C. indica exhibited relatively lesser ROS accumulation and oxidative damage during the experimental phase than other selected plants. The study also showed that plant biomass, transpiration rate, chlorophyll content, root exudates, and root activity influenced the removal of CBZ by various plants (r – 0.76 to 0.98, P < 0.05). The mass balance analysis indicated that a significant proportion of CBZ (49.2 to 72.7 %) underwent metabolism in the plant tissues. Apart from higher removal, lesser accumulation, and lower oxidation stress, multi-criteria decision analysis showed that C. indica is a potential plant species for the removal of CBZ.

Recently, the biotransformation of sulfamethoxazole (SMX) by microalgae has attracted increasing interest. In particular, cytochrome P450 (CYP450) has been suggested to be the main enzymatic contributor to this biodegradation. However, the molecular evidence of CYP450 enzymes being involved in SMX biodegradation remains relatively unclear, hindering its applicability. Herein, the biodegradation of SMX by Chlorella sorokiniana (C. sorokiniana) was investigated, and comprehensively elucidated the reaction mechanism underlying CYP450-mediated SMX metabolism. C. sorokiniana was able to efficiently remove over 80% of SMX mainly through biodegradation, in which CYP450 enzymes responded substantially to metabolize SMX in cells. Additionally, screening of transformation products (TPs) revealed that N⁴-hydroxylation-SMX (TP270) was the main TP in the SMX biodegradation pathway of microalgae. Molecular dynamics (MD) simulation suggested that the aniline of SMX was the most prone to undergo metabolism, while density functional theory (DFT) indicated that SMX was metabolized by CYP450 enzymes through H-abstraction-OH-rebound reaction. Collectively, this work reveals key details of the hydroxylamine group of SMX, elucidates the SMX biodegradation pathway involving CYP450 in microalgae in detail, and accelerates the development of using microalgae-mediated CYP450 to eliminate antibiotics.

The objective of this research was to evaluate the efficacy of cinnamon wood biochar (CWBC) in adsorbing sulfamethoxazole (SUL), which alleviates bioavailability and plant uptake. Batch studies at various pH, contact times, and initial SUL loading were used to study SUL adsorption in CWBC, soil, and 2.5% CWBC amended soil. SUL mitigation from plant uptake were examined using Ipomoea aquatica at different SUL contamination levels in the soil. The kinetic results were described by pseudo-second-order with maximum adsorption capacities ($Q_{max}$) of 95.64 and 0.234mg/g for pristine CWBC and amendment, respectively implying that chemical interactions are rate-determining stages. Hill and Toth's model described the isotherm data for pristine CWBC, soil and CWBC amended soil as $Q_{max}$ of 113.44, 0.72, and 3.45mg/g. Column data showed a great mobilization of SUL in loamy sand; however, when CWBC was added to the loamy sand, the mobilization was drastically reduced by 98.8%. The Ipomoea aquatica showed a great potential to SUL uptake and it depended on the contamination level; the SUL accumulation in plant was 9.6–13.8 and 19.1–48mg/kg when soil was spiked with 5 and 50mg/kg, respectively. The addition of 2.5% CWBC reduced root and shoot uptake by 30 and 95%, respectively in 5mg/kg of SUL, whereas with 50mg/kg of SUL, the root and shoot uptake was reduced by 60 and 61%, respectively. The current study suggested CWBC as a possible adsorbent that may be employed to reduce SUL bioavailability in environmental matrices.

The mutual interaction of a microalga Chlorella vulgaris with four antibiotics viz. sulfamethoxazole (SMX), trimethoprim (TMP), azithromycin (AZI), and levofloxacin (LEV) individually and in mixture was studied in batch culture. SMX, TMP, and LEV stimulated algal growth, while AZI inhibited its growth. The Combination Index (CI)-isobologram indicated antagonism of the antibiotic mixture on the growth of C. vulgaris. Higher removal efficiency was observed in the mixed antibiotic than in the single antibiotic batch cultures. Biodegradation was the main antibiotic removal mechanism with a similar antibiotic biosorption pattern in single and mix antibiotic cultures. Scanning electron microscopy and Fourier transform infrared spectrophotometry showed minor biochemical alterations on algal cells surface and a stable algal population. Monod kinetics model was successfully applied to understand the growth with respect to the removal efficiency of C. vulgaris in single and mix antibiotic batch cultures. Results indicated relatively higher specific growth rate in the mix antibiotic batch culture with removal efficiency in the order of SMX>LEV>TMP>AZI. In total, 46 metabolites with 18 novel ones of the four antibiotics were identified by using high-resolution mass spectrometry based on the suspect screening approach to propose the potential transformation pathways. Most of the transformation products demonstrated lower toxicity than their respective parents. These findings implied that C. vulgaris could be an outstanding candidate for advanced treatment of antibiotic removal in wastewater.

Environmental Pollution, Volume 242, Part B, 2018, pp. 1758-1767

In current study, we investigated the changes of proteome profiles of Pycnoporus sanguineus after a single exposure of Cr(VI), TBBPA and a combined exposure of TBBPA and Cr(VI), with the goal of illuminating the cellular mechanisms involved in the interactions of co-existed TBBPA and Cr(VI) with the cells of P.sanguineus at the protein level. The results revealed that some ATP-binding cassette (ABC) transporters were obviously induced by these pollutants to accelerate the transportation, transformation and detoxification of TBBPA and Cr(VI). Cr(VI) could inhibit the bioremoval of its organic co-pollutants TBBPA through suppressing the expression of several key proteins related to the metabolism of TBBPA by P.sanguineus, including two cytochrome P450s, pentachlorophenol 4-monooxygenase and glutathione S-transferases. Furthermore, Cr(VI) possibly reduced the cell vitality and growth of P.sanguineus by enhancing the expression of imidazole glycerol phosphate synthase as well as by decreasing the abundances of proteins associated with the intracellular metabolic processes, such as the tricarboxylic acid cycle, purine metabolism and glutathione biosynthesis, thereby adversely affecting the biotransformation of TBBPA. Cr(VI) also inhibited the expression of peptidyl prolyl cis/trans isomerases, thus causing the damage of cell membrane integrity. In addition, some important proteins participated in the resistance to Cr(VI) toxicity were observed to up-regulate, including heat shock proteins, 26S proteasome, peroxiredoxins and three critical proteins implicated in S-adenosyl methionine synthesis, which contributed to reducing the hazard of Cr(VI) to P.sanguineus. The results of this study provide novel insights into the physiological responses and molecular mechanism of white rot fungi P.sanguineus to the stress of concomitant TBBPA and Cr(VI).

Chemosphere, Volume 191, 2018, pp. 607-615

Environmental Pollution, Volume 220, Part A, 2017, pp. 400-406

The increasing discharge of pharmaceuticals and personal care products (PPCPs) into the environment has generated serious public concern. The recent awareness of the environmental impact of this emerging class of pollutants and their potential adverse effects on human health have been documented in many reports. However, information regarding uptake and intracellular distribution of PPCPs in hydrophytes under hydroponic conditions, and potential human exposure is very limited. A laboratory experiment was conducted using ¹⁴C-labeled triclosan (TCS) to investigate uptake and distribution of TCS in six aquatic plants (water spinach, purple perilla, cress, penny grass, cane shoot, and rice), and the subcellular distribution of ¹⁴C-TCS was determined in these plants. The results showed that the uptake and removal rate of TCS from nutrient solution by hydrophytes followed the order of cress (96%)>water spinach (94%)>penny grass (87%)>cane shoot (84%)>purple perilla (78%)>rice (63%) at the end of incubation period (192h). The range of ¹⁴C-TCS content in the roots was 94.3%–99.0% of the added ¹⁴C-TCS, and the concentrations in roots were 2–3 orders of magnitude greater than those in shoots. Furthermore, the subcellular fraction-concentration factor (3.6×10²–2.6×10³mLg⁻¹), concentration (0.58–4.47μgg⁻¹), and percentage (30%–61%) of ¹⁴C-TCS in organelles were found predominantly greater than those in cell walls and/or cytoplasm. These results indicate that for these plants, the roots are the primary storage for TCS, and within plant cells organelles are the major domains for TCS accumulation. These findings provide a better understanding of translocation and accumulation of TCS in aquatic plants at the cellular level, which is valuable for environmental and human health assessments of TCS.

Ecotoxicology and Environmental Safety, Volume 92, 2013, pp. 297-302

Uptake of three sulfonamides (SAs) including sulfadiazine (SDZ), sulfamethazine (SM₂) and sulfamethoxazole (SMZ) by pakchoi cabbage from soil was evaluated by using pot experiment. SDZ, SM₂ and SMZ spiked in soil could be taken up by pakchoi cabbage. SM₂ and SMZ were accumulated more easily by pakchoi cabbage than SDZ. The dissipation half-lives of SMZ (16.8d) and SM₂ (16.7d) in soil were significantly longer than SDZ (10.8d). The higher concentrations of SM₂ and SMZ in pakchoi cabbage in comparison with that of SDZ could be attributed to the higher residual concentrations of SM₂ and SMZ in soil. Increasing initial concentration of SM₂ spiked in soil, the residual concentration of SM₂ in soil increased and resulted in promoting SM₂ uptake in pakchoi cabbage. Concentrations of SAs in pakchoi cabbage planted in combined sulfonamides polluted soil differ from that in single sulfonamide polluted soil, although the same concentration (5.0mg/kg) of SAs was spiked in soil. Combined SAs pollution in soil may enhance SAs uptake in pakchoi cabbage. The lower bacteria numbers in soil under combined pollution resulted in higher residual SAs concentrations in soil, which could be the main reason for higher SAs concentrations in pakchoi cabbage.

Ecotoxicology and Environmental Safety, Volume 142, 2017, pp. 250-256

A pot experiment was carried out to investigate the single and combined effect of different concentrations of sulfadiazine (SDZ) (1 and 10mgkg⁻¹) and copper (Cu) (20 and 200mgkg⁻¹) stresses on growth, hydrogen peroxide (H₂O₂), malondialdehyde (MDA), antioxidant enzyme activities of wheat seedlings and their accumulation. High SDZ or Cu level significantly inhibited the growth of wheat seedlings, but the emergence rate was only inhibited by high SDZ level. The presence of Cu reduced the accumulation of SDZ, whereas the effect of SDZ on the accumulation of Cu depended on their concentrations. Low Cu level significantly increased the chlorophyll content, while high Cu level or both SDZ concentrations resulted in a significant decrease in the chlorophyll content as compared to the control. Additionally, H₂O₂ and MDA contents increased with the elevated SDZ or Cu level. The activities of superoxide dismutase, peroxidase and catalase were also stimulated by SDZ or Cu except for the aerial part treated by low Cu level and root treated by high SDZ level. The joint toxicity data showed that the toxicity of SDZ to wheat seedlings was generally alleviated by the presence of Cu, whereas the combined toxicity of SDZ and Cu was larger than equivalent Cu alone.

Chemosphere, Volume 253, 2020, Article 126695

Antibiotic pollution has become a hot issue worldwide, which has toxic effects on plants and even threatens human health. As a common wetland plant, the tolerance mechanism of Phragmites australis to antibiotics is rarely reported. In this study, we investigated the enrichment characteristics and biological response of P.australis to sulfamethoxazole (SMZ) and ofloxacin (OFL) residues, which are common in the environment. We found that the simulated concentration of antibiotics far exceeded the current level of antibiotic residues in the water environment, but it did not significantly inhibit the growth of P.australis. At 1mgL⁻¹, OFL and SMZ significantly increased the biomass of P.australis, which was mainly related to the improvement of root activity and photosynthetic efficiency, but the duplex treatment (SMZ+OFL) did not significantly stimulate the growth of reeds. OFL could significantly reduce the accumulation of reactive oxygen species (ROS) in P.australis. When OFL was 1mgL⁻¹, compared with control, superoxide anion and H₂O₂ were reduced by 11.19% and 10.76%, respectively, which was mainly related to the improvement of membrane stability. SMZ and SMZ+OFL had no significant effect on ROS, but they significantly increased antioxidant enzyme activity. SMZ and OFL could increase soil invertase, urease, and protease activities, and the tested antibiotics had no significant effect on the Shannon-Wiener index of soil microorganisms. The accumulation of antibiotics within tissues could be ranked as root>leaf>stem, and the accumulation and transport of OFL were higher than those of SMZ.