Biodegradation, photolysis, and sorption of antibiotics in aquatic environments: A scoping review

The treated wastewater enhances the biodegradation of sulfonamide antibiotics in biofilm-sediment downstream of the receiving river outlet

Although the treated wastewater meets the discharge standards, it can still become a potential transmitted stressor that affects aquatic organisms in receiving rivers. Biofilms and sediments as the main solid-phase substances in natural aquatic environments can biodegrade micropollutants. However, most of the current studies have selected a single solid-phase material, and there are relatively few studies that comprehensively consider the effect of treated wastewater on the dissipation of micropollutants in a composite biofilm-sediment system. Therefore, this study investigated the dissipation pathways of six sulfonamide antibiotics (SAs) in biofilm-sediment and the effect of treated wastewater on SAs dissipation. The results showed that biodegradation was the main pathway for SAs dissipation in biofilm-sediment. The input of treated wastewater increased the abundance of dominant degradation bacteria Burkholderiales and Pseudomonadale, thereby improving the biodegradation rate of SAs (approximately 1.5 times higher than upstream degradation rate). These genera could also be further integrated into downstream communities to continuously mediate the biodegradation of SAs. Through mass spectrometry and metagenomic sequencing analysis, it was found that the common degradation pathways of SAs in biofilm-sediment affected by treated wastewater are acetylation, formylation, hydroxylation, and bond cleavage. Acetyltransferase played an important role in the biodegradation of SAs. In addition, the enrichment of antibiotic resistant genes during biodegradation increased the risk of their spread in the aquatic environment. These findings provide new insights into the fate of antibiotics in aquatic environments and the impact of treated wastewater on downstream bacterial communities.

Biodegradation and bioaugmentation of the co-contamination of chloramphenicol and microplastics by Exiguobacterium sp. CAP4 isolated from a contaminated plastisphere

Microplastics (MPs) and antibiotics are newly emerging contaminants that have heavily accumulated in the environment and are a great cause of concern due to their co-contamination. Although the removal and degradation of individual MPs and antibiotics have been studied in various environments, our understanding of how to eliminate the co-contamination of MPs and antibiotics remains poor. In this study, the biodegradation of both micro polyethylene (mPE) and chloramphenicol (CAP) was analyzed in a wastewater sample. Members of the genera Exiguobacterium, Methanospirillum, Methanosaeta, and Candidatus Nitrocosmicus were proposed as biomarkers in plastisphere, which may contribute to the biodegradation of both contaminants. Notably, Exiguobacterium sp. CAP4 was isolated from the plastisphere and exhibited a high potential to degrade both CAP and mPE. Bioaugmentation with Exiguobacterium sp. CAP4 in mPEs and CAP contaminated wastewater facilitated the biodegradation of both mPE and CAP. This work expands the knowledge base regarding the simultaneous elimination of MPs and antibiotics in situ and identifies a promising bacterial strain for both MP and antibiotic biodegradation.

Photochemical transformation of the uricosuric drug benzbromarone in aqueous solutions exposed to UV irradiation

As one of benzophenone-derived drugs, benzbromarone (BBM) has been widely used to reduce blood uric acid, treat gout, and gouty arthritis. Understanding the transformation and fate of BBM in natural and engineered systems is critical for its ecological risk assessment. In this study, we systematically investigated the photochemical behavior of BBM in aqueous solutions under laboratory UV254 irradiation. UV-vis spectra show that an aqueous solution of BBM is capable of absorbing UV photons at 200-400 nm. Spectroscopic titration indicates that BBM with a pKa value of 4.83 ± 0.17 is present mainly as the phenolate form under circumneutral conditions. BBM undergoes rapid direct photolysis when exposed to UV254 irradiation and the quantum yields were determined to be 0.0105 and 0.0196 mol E-1 for phenol and phenolate forms, respectively. The heavy atom effect of bromine and spin-orbit coupling effect of aromatic ketone make dibromophenol and carbonyl moieties the critical chromophores accounting for the high photoreactivity of BBM. Laser flash photolysis and electron paramagnetic resonance studies suggest that the photolysis of BBM is initiated by ultrafast photodebromination and Norrish I cleavage. The high yield of bromide determined by ion chromatograph highlights the importance of photodebromination. Due to the light screening effect of wastewater components, the photolysis of BBM in hospital wastewater is inhibited. Photo-induced modification of the dibromophenol moiety of BBM likely generates photoproducts showing toxicity to luminescent bacteria. Overall, our results reveal that photochemical reaction under UV irradiation plays an important role in the attenuation of BBM in engineered water.

Aquatic photochemistry for different dissociation forms of cephalosporin antibiotics: Degradation kinetics, products and photo-modified toxicity

Cephalosporin antibiotics (CFs) with ionizable groups (-COOH and -NHn) are widely detected as emerging micropollutants that pose potential environmental risks to aquatic systems, but few studies have revealed their multivariate photochemical transformation behavior in sunlight-irradiated surface waters. In this study, the apparent photodegradation, photo-oxidation towards reactive oxygen species (ROS, •OH and 1O2), and photo-modified toxicity were investigated for the four ionizable CFs: cefoxitin (CFX), cephalothin (CEF), cefoperazone (CFP) and cefazolin (CFZ). Under simulated sunlight irradiation (λ > 290 nm), their multivariate photo-transformation kinetics varied as a function of pHs and the dominant protonated states of the CF in question (H2CFs+, HCFs0 and CFs-). Based on competition kinetics and matrix deconvolution methods, the apparent photolytic rate constants (ki) of different dissociation forms were found to decrease gradually from H2CFs+ to CFs- then to HCFs0, which was dominated by the changing cumulative light absorption (∑(Lλελ,i)) for the different dissociated forms. Interestingly, it was observed that the H2CFs+ or CFs- exhibited higher reactivities towards •OH, while CFs- demonstrated the fastest reaction with 1O2. Using the theoretical derivation, the determined environmental half-lives of the CFs in sunlight-irradiated surface waters were closely dependent on the water pHs and multiple photochemical reaction types. In most cases, apparent photodegradation contributes more than ROS mediated photooxidation to the overall photo-transformation of CFs. The product identification using HPLC-MS/MS indicated that the photodegradation pathways mainly involved photoinduced hydrolysis of the β-lactam ring, cleavage of the side-chain, and decarboxylation. Based on the bioassay to Vibrio fischeri, the most CFs showed photo-enhanced toxicity, which was verified by the ECOSAR assessment, raising concerns about the formation and accumulation of more toxic intermediates. These results are of significance to better assessing the photochemical persistence and risk of the CFs in the aquatic systems and wastewater treatment.

Effect of antibiotics on diverse aquatic plants in aquatic ecosystems

The widespread presence of antibiotics in aquatic ecosystems, mainly due to their use in medicine and veterinary practices, poses a significant environmental challenge. Aquatic plants play a vital role in maintaining ecosystem stability, but their responses to antibiotics vary by species, influenced by differences in their traits and interactions with environmental factors. However, the specific ways antibiotics affect these plants remain poorly understood. In this study, we conducted a meta-analysis of 167 peer-reviewed studies to investigate the mechanisms of antibiotic uptake and their effects on different types of aquatic plants-submerged, emergent, and floating. Our analysis shows that antibiotics, particularly common ones like sulfonamides, tetracyclines, and quinolones, impact aquatic plants through multiple pathways. Submerged and floating plants often face widespread, direct exposure, resulting in "full-coverage" impacts, while emergent plants experience mixed exposure patterns, affecting both submerged and aerial parts and leading to "partial-coverage" impacts. These findings provide a foundation for phytoremediation strategies, enabling the rational selection and management of aquatic plant types to mitigate antibiotic pollution. Our study underscores the ecological risks posed by antibiotic contamination in aquatic ecosystems and offers a theoretical framework for developing effective restoration strategies.

Biotransformation of chloramphenicol by enriched bacterial consortia and the newly isolated bacterial strain Bordetella sp. C3: Detoxifying biotransformation pathway and its potential application in agriculture

Limited sources of consortia/pure cultures that degrade chloramphenicol (CAP) and the incomplete biodegradation profiles of CAP hinder the remediation of CAP pollution. In this study, two CAP-degrading consortia (designated as CM and PM) were obtained after long-term acclimation, and Alcaligenaceae and Enterobacteriaceae enriched in CM and PM, respectively. Notably, Bordetella sp. C3, a new isolate belonging to the family Alcaligenaceae, was isolated from CM and capable of degrading 85.7 % 10 mg/L CAP at 30 ℃ and pH 7 in 10 d. The biotransformation of CAP by Bordetella sp. C3 was proposed as a detoxification process, including a novel initial degradation pathway: dechlorination of CAP into AP. Strain C3 can also function as a plant growth-promoting bacterium that solubilizes inorganic phosphate and produces siderophores and indole-3-acetic acid (IAA). This study expands our knowledge of the migration and transformation pathways of CAP and microbial community profiles during acclimatization.

Photodegradation potential of selected non-steroidal anti-inflammatory drugs in a middle-order Alpine river downstream of a wastewater treatment plant, during a year of enduring water scarcity

The year 2022 was characterised by significant water shortages and droughts in Italy, with the most pronounced impact observed in the North-Western regions, including Piemonte. In conditions of water scarcity, treated wastewater undergoes little dilution by natural flows and this can deeply affect the chemistry of water-poor rivers and streams. However, increased pollution by wastewater would be partially offset by fast photodegradation of pollutants in shallow water and by the longer time allowed to photochemical reactions if water flows more slowly. We assessed the latter phenomena in the Stura di Lanzo, a middle-order Alpine river tributary of the largest Italian river, the Po, and affected by a wastewater treatment plant (WWTP). In 2022, the concentration values of the photochemically significant parameters nitrate, nitrite, and DOC were usually higher downstream of the WWTP outlet, which could slightly favour indirect photodegradation reactions. Direct and indirect photodegradation was assessed for the non-steroidal anti-inflammatory drugs paracetamol, diclofenac, and naproxen, all undergoing rather fast photoreactions. Photochemistry model results show that the three compounds would undergo 10-40 % photodegradation in spring and summer along the stretch separating the wastewater outlet from the confluence of Stura into the Po. Photodegradation would continue in the latter, but other WWTPs might contribute additional pollution in the meanwhile. Albeit significant, photodegradation could only partially promote the elimination of the contaminants.

Occurrence and environmental fate of anti-influenza drugs in a subcatchment of the Yodo River Basin, Japan

Understanding the current situation and risk of environmental contamination by anti-influenza drugs in aquatic environments is key to prevent the unexpected emergence and spread of drug-resistant viruses. However, few reports have been focused on newer drugs that have recently been introduced in clinical settings. In this study, the behaviour of the prodrug baloxavir marboxil (BALM)-the active ingredient of Xofluza, an increasingly popular anti-influenza drug-and its pharmacologically active metabolite baloxavir (BAL) in the aquatic environment was evaluated. Additionally, their presence in urban rivers and a wastewater treatment plant (WWTP) in the Yodo River basin was investigated and compared with those of the major anti-influenza drugs used to date (favipiravir (FAV), peramivir (PER), laninamivir (LAN), and its active metabolite, laninamivir octanoate (LANO), oseltamivir (OSE), and its active metabolite, oseltamivir carboxylate (OSEC), and zanamivir (ZAN)) to comprehensively assess their environmental fate in the aquatic environment. The results clearly showed that BALM, FAV, and BAL were rapidly degraded through photolysis (2-h, 0.6-h, and 0.4-h half-lives, respectively), followed by LAN, which was gradually biodegraded (7-h half-life). In addition, BALM and BAL decreased by up to 47 % after 4 days and 34 % after 2 days of biodegradation in river water. However, the remaining conventional drugs, except for LANO (<1 % after 10 days), were persistent, being transported from the upstream to downstream sites. The LogKd values for the rates of sorption of BALM (0.5-1.6) and BAL (1.8-3.1) on river sediment were higher than those of conventional drugs (-0.5 to 1.7). Notably, all anti-influenza drugs were effectively removed by ozonation (>90-99.9 % removal) after biological treatment at a WWTP. Thus, these findings suggest the importance of introducing ozonation to reduce pollution loads in rivers and the environmental risks associated with drug-resistant viruses in aquatic environments, thereby promoting safe river environments.

Comprehensive analysis and risk assessment of Antibiotic contaminants, antibiotic-resistant bacteria, and resistance genes: Patterns, drivers, and implications in the Songliao Basin

The pervasive use of antibiotics has raised substantial environmental concerns, especially regarding their temporal and spatial distribution across diverse water systems. This study addressed the gap in comprehensive research on antibiotic contamination during different hydrological periods, focusing on the Jilin section of the Songliao Basin in Northeast China, an area with severe winter ice cover. The study examined the occurrence, distribution, influencing factors, and potential ecological risks of prevalent antibiotic contaminants. Findings revealed antibiotic concentrations ranging from 239.64 to 965.81 ng/L, with antibiotic resistance genes (ARGs) at 5.22 × 10-2 16S rRNA-1 and antibiotic-resistant bacteria (ARB) up to 5.76 log10 CFU/mL. Ecological risk assessments identified significant risks to algae from oxytetracycline, erythromycin, and amoxicillin. Redundancy analysis and co-occurrence networks with ordinary least squares (OLS) demonstrated that the dispersion of ARGs and ARB is significantly influenced by environmental factors such as total organic carbon (TOC), total phosphorus (TP), total nitrogen (TN), fluoride (F⁻), and nitrate (NO₃⁻). These elements, along with mobile genetic elements (MGEs), play crucial roles in ARG patterns (R2 = 0.94, p ≤ 0.01). This investigation offers foundational insights into antibiotic pollution dynamics in cold climates, supporting the development of targeted mitigation strategies for aquatic systems.

Source elimination of antibiotic resistance risk in aquaculture water by VUV/sulfite pretreatment

Antibiotic resistance risk in the aquaculture industry is increasing with the excessive consumption of antibiotics. Although various efficient technologies for the degradation of antibiotics are available, the potential risk from antibiotic resistance in treated waters is often overlooked. This study compared the risks of antibiotic resistance in anaerobic sludge fed with pretreated florfenicol (FLO) containing wastewater after four UV or vacuum UV (VUV)-driven ((V)UV-driven) pretreatments, and established the VUV/sulfite recirculating water system to validate the effect of controlling the antibiotic resistance risk in the actual aquaculture water. Metagenomics sequencing revealed that a remarkable decrease in the abundance of antibiotic resistance genes (ARGs) was observed in four different pretreated groups, and results among the four pretreated groups were sorted in descending order based on ARG abundance: UV > VUV > UV/sulfite > VUV/sulfite. The low abundance of ARGs from VUV/sulfite group was close to that in the CK group (wastewater without FLO and without any pretreatments), which was 0.41 copies/cell. From the perspective of the temporal changes in the relative abundance of floR, the abundance in VUV/sulfite group remained lower than 11.67 ± 0.73 during the cultivation time. Additionally, microbial diversity analysis found that Proteobacteria and Firmicutes were major carriers of ARGs. Two species from Burkholderiaceae and Rhodocyclales were identified as potential co-hosts to spread by the correlation analysis of the abundances between floR or intI1 and the top 50 genera. Finally, the abundances of ARGs and MGEs in the VUV/sulfite recirculating water system with actual aquaculture water were reduced by 39.15% and 46.04%, respectively, compared to that in the blank group without any pretreatment. This study verified that VUV/sulfite pretreatment system could effectively control the antibiotic resistance risk of ARGs proliferation and transfer in aquaculture water. Furthermore, the study demonstrated that the reduction of antibiotic antibacterial activity plays an important role in the source control of resistance risk.

Green solutions for antibiotic pollution: Assessing the phytoremediation potential of aquatic macrophytes in wastewater treatment plants

We compared the ability of one emergent (Sagittaria montevidensis), two floating (Salvinia minima and Lemna gibba), and one heterophyllous species (Myriophyllum aquaticum) to simultaneously remove sulfamethoxazole, sulfadiazine, ciprofloxacin, enrofloxacin, norfloxacin, levofloxacin, oxytetracycline, tetracycline, doxycycline, azithromycin, amoxicillin, and meropenem from wastewater in a mesocosm-scale constructed wetland over 28 days. Antibiotic concentrations in plants and effluent were analyzed using an LC-MS/MS to assess the removal rates and phytoremediation capacities. M. aquaticum did not effectively mitigate contamination due to poor tolerance and survival in effluent conditions. S. minima and L. gibba demonstrated superior efficiency, reducing the antibiotic concentrations to undetectable levels within 14 days, while S. montevidensis achieved this result by day 28. Floating macrophytes emerge as the preferable choice for remediation of antibiotics compared to emergent and heterophyllous species. Antibiotics were detected in plant tissues at concentrations ranging from 0.32 to 29.32 ng g-1 fresh weight, highlighting macrophytes' ability to uptake and accumulate these contaminants. Conversely, non-planted systems exhibited a maximum removal rate of 65%, underscoring the persistence of these molecules in natural environments, even after the entire experimental period. Additionally, macrophytes improved effluent quality regardless of species by reducing total soluble solids and phosphate concentrations and mitigating ecotoxicological effects. This study underscores the potential of using macrophytes in wastewater treatment plants to enhance overall efficiency and prevent environmental contamination by antibiotics, thereby mitigating the harmful impact on biota and antibiotic resistance. Selecting appropriate plant species is crucial for successful phytoremediation in constructed wetlands, and actual implementation is essential to validate their effectiveness and practical applicability.

Transformation of antibiotics to non-toxic and non-bactericidal products by laccases ensure the safety of Stropharia rugosoannulata

The substantial use of antibiotics contributes to the spread and evolution of antibiotic resistance, posing potential risks to food production systems, including mushroom production. In this study, the potential risk of antibiotics to Stropharia rugosoannulata, the third most productive straw-rotting mushroom in China, was assessed, and the underlying mechanisms were investigated. Tetracycline exposure at environmentally relevant concentrations (<500 μg/L) did not influence the growth of S. rugosoannulata mycelia, while high concentrations of tetracycline (>500 mg/L) slightly inhibited its growth. Biodegradation was identified as the main antibiotic removal mechanism in S. rugosoannulata, with a degradation rate reaching 98.31 % at 200 mg/L tetracycline. High antibiotic removal efficiency was observed with secreted proteins of S. rugosoannulata, showing removal efficiency in the order of tetracyclines > sulfadiazines > quinolones. Antibiotic degradation products lost the ability to inhibit the growth of Escherichia coli, and tetracycline degradation products could not confer a growth advantage to antibiotic-resistant strains. Two laccases, SrLAC1 and SrLAC9, responsible for antibiotic degradation were identified based on proteomic analysis. Eleven antibiotics from tetracyclines, sulfonamides, and quinolones families could be transformed by these two laccases with degradation rates of 95.54-99.95 %, 54.43-100 %, and 5.68-57.12 %, respectively. The biosafety of the antibiotic degradation products was evaluated using the Toxicity Estimation Software Tool (TEST), revealing a decreased toxicity or no toxic effect. None of the S. rugosoannulata fruiting bodies from seven provinces in China contained detectable antibiotic-resistance genes (ARGs). This study demonstrated that S. rugosoannulata can degrade antibiotics into non-toxic and non-bactericidal products that do not accelerate the spread of antibiotic resistance, ensuring the safety of S. rugosoannulata production.

Occurrence and dissemination of antibiotics and antibiotic resistance in aquatic environment and its ecological implications: a review

The occurrence of antibiotics and antibiotic-resistant bacteria (ARBs), genes (ARGs), and mobile genetic elements (MGEs) in aquatic systems is growing global public health concern. These emerging micropollutants, stemming from improper wastewater treatment and disposal, highlight the complex and evolving nature of environmental pollution. Current literature reveals potential biases, such as a geographical focus on specific regions, leading to an insufficient understanding of the global distribution and dynamics of antibiotic resistance in aquatic systems. There is methodological inconsistency across studies, making it challenging to compare findings. Potential biases include sample collection inconsistencies, detection sensitivity variances, and data interpretation variability. Gaps in understanding include the need for comprehensive, standardized long-term monitoring programs, elucidating the environmental fate and transformation of antibiotics and resistance genes. This review summarizes current knowledge on the occurrence and dissemination of emerging micropollutants, their ecological impacts, and the global health implications of antimicrobial resistance. It highlights the need for interdisciplinary collaborations among researchers, policymakers, and stakeholders to address the challenges posed by antibiotic resistance in aquatic resistance in aquatic systems effectively. This review highlights widespread antibiotic and antibiotic resistance in aquatic environment, driven by human and agricultural activities. It underscores the ecological consequences, including disrupted microbial communities and altered ecosystem functions. The findings call for urgent measures to mitigate antibiotics pollution and manage antibiotic resistance spread in water bodies.