Determination of the fate of antibiotic resistance genes and the response mechanism of plants during enhanced antibiotic degradation in a bioelectrochemical-constructed wetland system

Enhanced removal of PPCPs and antibiotic resistance genes in saline wastewater using a bioelectrochemical-constructed wetland system

Pharmaceuticals and personal care products (PPCPs) are insufficiently degraded in saline wastewater treatment processes and are found at high concentrations and detection frequencies in aquatic environments. In this study, the wetland plant Thalia dealbata was selected using a screening plant experiment to ensure good salt tolerance and high efficiency in removing PPCPs. An electric integrated vertical-flow constructed wetland (E-VFCW) was developed to improve the removal of PPCPs and reduce the abundance of antibiotic resistance genes (ARGs). The removal efficiency of ofloxacin, enrofloxacin, and diclofenac in the system with anaerobic cathodic and aerobic anodic chambers is higher than that of the control system (41.84 ± 2.88%, 47.29 ± 3.01%, 53.29 ± 2.54%) by approximately 20.31%, 16.04%, and 35.25%. The removal efficiency of ibuprofen in the system with the aerobic anodic and anaerobic cathodic chamber was 28.51% higher than that of the control system (72.41 ± 3.06%) and promotes the reduction of ARGs. Electrical stimulation can increase the activity of plant enzymes, increasing their adaptability to stress caused by PPCPs, and PPCPs are transferred to plants. Species related to PPCPs biodegradation (Geobacter, Lactococcus, Hydrogenophaga, and Nitrospira) were enriched in the anodic and cathodic chambers of the system. This study provides an essential reference for the removal of PPCPs in saline-constructed wetlands.

Ciprofloxacin affects nutrient removal in manganese ore-based constructed wetlands: Adaptive responses of macrophytes and microbes

Ciprofloxacin (CIP) has received considerable attention in recent decades due to its high ecological risk. However, little is known about the potential response of macrophytes and microbes to varying levels of CIP exposure in constructed wetlands. Therefore, lab-scale manganese ore-based tidal flow constructed wetlands (MO-TFCWs) were operated to evaluate the responses of macrophytes and microbes to CIP over the long term. The results indicated that total nitrogen removal improved from 79.93% to 87.06% as CIP rose from 0 to 4 mg L-1. The chlorophyll content and antioxidant enzyme activities in macrophytes were enhanced under CIP exposure, but plant growth was not inhibited. Importantly, CIP exposure caused a marked evolution of the substrate microbial community, with increased microbial diversity, expanded niche breadth and enhanced cooperation among the top 50 genera, compared to the control (no CIP). Co-occurrence network also indicated that microorganisms may be more inclined to co-operate than compete. The abundance of the keystone bacterium (involved in nitrogen transformation) norank_f__A0839 increased from 0.746% to 3.405%. The null model revealed drift processes (83.33%) dominated the community assembly with no CIP and 4 mg L-1 CIP. Functional predictions indicated that microbial carbon metabolism, electron transfer and ATP metabolism activities were enhanced under prolonged CIP exposure, which may contribute to nitrogen removal. This study provides valuable insights that will help achieve stable nitrogen removal from wastewater containing antibiotic in MO-TFCWs.

Facile synthesis of lignin-based Fe-MOF for fast adsorption of methyl orange

To rapidly remove dyes from wastewater, iron-based metal-organic frameworks modified with phenolated lignin (NH2-MIL@L) were prepared by a one-step hydrothermal method. Analyses of the chemical structure and adsorption mechanism of the NH2-MIL@L proved the successful introduction of lignin and the enhancement of its adsorption sites. Compared with NH2-MIL-101-Fe without phenolated lignin, the modification with lignin increased the methyl orange (MO) adsorption rate of NH2-MIL@L. For the best adsorbent, NH2-MIL@L4, the MO adsorption efficiency in MO solution reached 95.09% within 5 min. NH2-MIL@L4 reached adsorption equilibrium within 90 min, exhibiting an MO adsorption capacity of 195.31 mg/g. The process followed pseudo-second-order kinetics and the Dubinin-Radushkevich model. MO adsorption efficiency of NH2-MIL@L4 was maintained at 89.87% after six adsorption-desorption cycles. In mixed solutions of MO and methylene blue (MB), NH2-MIL@L4 achieved an MO adsorption of 94.02% at 5 min and reached MO adsorption equilibrium within 15 min with an MO adsorption capacity of 438.6 mg/g, while the MB adsorption equilibrium was established at 90 min with an MB adsorption rate and capacity of 95.60% and 481.34 mg/g, respectively. NH2-MIL@L4 sustained its excellent adsorption efficiency after six adsorption-desorption cycles (91.2% for MO and 93.4% for MB). The process of MO adsorption by NH2-MIL@L4 followed the Temkin model and pseudo-second-order kinetics, while MB adsorption followed the Dubinin-Radushkevich model and pseudo-second-order kinetics. Electrostatic interactions, π-π interactions, hydrogen bonding, and synergistic interactions affected the MO adsorption process of NH2-MIL@L4.

A review on the alternatives to antibiotics and the treatment of antibiotic pollution: Current development and future prospects

Antibiotics, widely used in the fields of medicine, animal husbandry, aquaculture, and agriculture, pose a serious threat to the ecological environment and human health. To prevent antibiotic pollution, efforts have been made in recent years to explore alternative options for antibiotics in animal feed, but the effectiveness of these alternatives in replacing antibiotics is not thoroughly understood due to the variation from case to case. Furthermore, a systematic summary of the specific applications and limitations of antibiotic removal techniques in the environment is crucial for developing effective strategies to address antibiotic contamination. This comprehensive review summarized the current development and potential issues on different types of antibiotic substitutes, such as enzyme preparations, probiotics, and plant extracts. Meanwhile, the existing technologies for antibiotic residue removal were discussed under the scope of application and limitation. The present work aims to highlight the strategy of controlling antibiotics from the source and provide valuable insights for green and efficient antibiotic treatment.

Nano-CeO2 activates physical and chemical defenses of garlic (Allium sativum L.) for reducing antibiotic resistance genes in plant endosphere

The transmission of manure- and wastewater-borne antibiotic-resistant bacteria (ARB) to plants contributes to the proliferation of antimicrobial resistance in agriculture, necessitating effective strategies for preventing the spread of antibiotic resistance genes (ARGs) from ARB in the environment to humans. Nanomaterials are potential candidates for efficiently controlling the dissemination of ARGs. The present study investigated the abundance of ARGs in hydroponically grown garlic (Allium sativum L.) following nano-CeO2 (nCeO2) application. Specifically, root exposure to nCeO2 (1, 2.5, 5, 10 mg L-1, 18 days) reduced ARG abundance in the endosphere of bulbs and leaves. The accumulation of ARGs (cat, tet, and aph(3')-Ia) in garlic bulbs decreased by 24.2-32.5 % after nCeO2 exposure at 10 mg L-1. Notably, the lignification extent of garlic stem-disc was enhanced by 10 mg L-1 nCeO2, thereby accelerating the formation of an apoplastic barrier to impede the upward transfer of ARG-harboring bacteria to garlic bulbs. Besides, nCeO2 upregulated the gene expression related to alliin biosynthesis and increased allicin content by 15.9-16.2 %, promoting a potent antimicrobial defense for reducing ARG-harboring bacteria. The potential exposure risks associated with ARGs and Ce were evaluated according to the estimated daily intake (EDI). The EDI of ARGs exhibited a decrease exceeding 95 %, while the EDI of Ce remained below the estimated oral reference dose. Consequently, through stimulating physical and chemical defenses, nCeO2 contributed to a reduced EDI of ARGs and Ce, highlighting its potential for controlling ARGs in plant endosphere within the framework of nano-enabled agrotechnology.

Vertical distribution characteristics and transport paths of antibiotic resistance genes in constructed wetland system

Although the migration and diffusion of antibiotic resistance genes (ARGs) in soil-plant systems have attracted much attention, the migration and diffusion characteristics between constructed wetlands and soil-plant systems differ greatly. Therefore, it is necessary to conduct research on vertical transmission and diffusion of ARGs in constructed wetlands. The vertical distribution and transmission of ARGs in constructed wetlands were explored via metagenomic analysis. The results showed that the proportion of multidrug ARGs was the largest, ranging from 24.2% to 47.5%. The shared characteristics of ARGs were similar to those of bacteria, and there were fewer unique ARGs and microbial species in mesophyll tissue. Sourcetracker analysis revealed that ARGs transfer between plants and atmosphere was bidirectional, but the diffusion of ARGs to atmosphere through plants was relatively weak. ARGs were mainly transmitted to atmosphere/surrounding environment through substrate and influent, and the contributions of substrate to ARGs in atmosphere/surrounding environment were 59.2% and 78.6%, respectively. ARGs involved in foliar attachment mainly originated from peripheral inputs. ARGs showed nonspecific selection for the host at phylum, class and order levels. These findings suggest that more attention should be given to the potential risks of ARGs in constructed wetlands, to formulate effective control and management strategies.

Dynamic evolution of antibiotic resistance genes in plastisphere in the vertical profile of urban rivers

Microplastics (MPs) can vertically transport in the aquatic environment due to their aging and biofouling, forming distinct plastisphere in different water layers. However, even though MPs have been regarded as hotspots for antibiotic resistance genes (ARGs), little is known about the propagation and transfer of ARGs in plastisphere in waters, especially in the vertical profile. Therefore, this study investigated the dynamic responses and evolution of ARGs in different plastisphere distributed vertically in an urbanized river. The biofilm biomass in the polylactic acid (PLA) plastisphere was relatively higher than that in the polyethylene terephthalate (PET), showing depth-decay variations. The ARGs abundance in plastisphere were much higher than that in the surrounding waters, especially for the PLA. In the vertical profiles, the ARGs abundance in the PET plastisphere increased with water depths, while the highest abundance of ARGs in the PLA mostly appeared at intermediate waters. In the temporal dynamic, the ARGs abundance in plastisphere increased and then decreased, which may be dominated by the MP types at the initial periods. After long-term exposure, the influences of water depths seemed to be strengthened, especially in the PET plastisphere. Compared with surface waters, the microbiota attached in plastisphere in deep waters showed high species richness, strong diversity, and complex interactions, which was basically consistent with the changes of nutrient contents in different water layers. These vertical variations in microbiota and nutrients (e.g., nitrogen) may be responsible for the propagation of ARGs in plastisphere in deep waters. The host bacteria for ARGs in plastisphere was also developed as water depth increased, leading to an enrichment of ARGs in deep waters. In addition, the abundance of ARGs in plastisphere in bottom waters was positively correlated with the mobile genetic elements (MGEs) of intI1 and tnpA05, indicative of a frequent horizontal gene transfer of ARGs. Overall, water depth played a critical role in the propagation of ARGs in plastisphere, which should not be ignored in a long time series. This study provides new insights into the dynamic evolution of ARGs propagation in plastisphere under increasing global MPs pollution, especially in the vertical profile.

The interactions between aquatic plants and antibiotics: Progress and prospects

Antibiotics have emerged as a widespread pollutant in the aquatic environment. Aquatic phytoremediation to remove antibiotic pollution in water has aroused increasing research. Due to complex interaction between aquatic plants and antibiotics in the aquatic environment, it is essential to summarize the present research progress and point out the shortcomings to better use aquatic plants to remediate antibiotic pollution. A growing body of evidence indicates roots are the most important tissues for aquatic plants to absorb and accumulate antibiotics and antibiotics can be transferred in aquatic plants. LogKow value is an important factor to affecting the antibiotic absorption by aquatic plant. The study showed that antibiotics have toxic effects on aquatic plants, including metabolic interference, oxidative damage, damage to photosynthetic system, and inhibition of growth. However, the species sensitivity distribution model indicated that the general environmental concentrations of antibiotics pose no risk to aquatic plant growth. Aquatic plants can significantly reduce the antibiotics concentration in water and the removal efficiency is affected by many factors, such as the type of aquatic plants and antibiotics. Macrolide antibiotics are most easily removed by plants. This study reviewed the current research progress and provides valuable scientific recommendations for further research.