Integrative chemical and multiomics analyses of tetracycline removal mechanisms in Pseudomonas sp. DX-21

Tetracycline (TC), widely found in various environments, poses significant risks to ecosystems and human health. While efficient biodegradation removes TC, the mechanisms underlying this process have not been elucidated. This study investigated the molecular mechanisms underlying TC biosorption and transfer within the extracellular polymeric substances (EPS) of strain DX-21 and its biodegradation process using fourier transform infrared spectroscopy, molecular docking, and multiomics. Under TC stress, DX-21 increased TC biosorption by secreting more extracellular polysaccharides and proteins, particularly the latter, mitigating toxicity. Moreover, specialized transporter proteins with increased binding capacity facilitated TC movement from the EPS to the cell membrane and within the cell. Transcriptomic and untargeted metabolomic analyses revealed that the presence of TC led to the differential expression of 306 genes and significant alterations in 37 metabolites. Notably, genes related to key enzymes, such as electron transport, peroxidase, and oxidoreductase, exhibited significant differential expression. DX-21 combated and degraded TC by regulating metabolism, altering cell membrane permeability, enhancing oxidative defense, and enhancing energy availability. Furthermore, integrative omics analyses indicated that DX-21 degrades TC via various enzymes, reallocating resources from other biosynthetic pathways. These results advance the understanding of the metabolic responses and regulatory mechanisms of DX-21 in response to TC.

Detoxification of tetracycline and synthetic dyes by a newly characterized Lentinula edodes laccase, and safety assessment using proteomic analysis

Fungal laccase has strong ability in detoxification of many environmental contaminants. A putative laccase gene, LeLac12, from Lentinula edodes was screened by secretome approach. LeLac12 was heterogeneously expressed and purified to characterize its enzymatic properties to evaluate its potential use in bioremediation. This study showed that the extracellular fungal laccase from L. edodes could effectively degrade tetracycline (TET) and the synthetic dye Acid Green 25 (AG). The growth inhibition of Escherichia coli and Bacillus subtilis by TET revealed that the antimicrobial activity was significantly reduced after treatment with the laccase-HBT system. 16 transformation products of TET were identified by UPLC-MS-TOF during the laccase-HBT oxidation process. Gas chromatography-mass spectrometry (GC-MS) analysis revealed that LeLac12 could completely mineralize ring-cleavage products. LeLac12 completely catalyzed 50 mg/L TET within 4 h by adding AG (200 mg/L), while the degradation of AG was above 96% even in the co-contamination system. Proteomic analysis revealed that central carbon metabolism, energy metabolism, and DNA replication/repair were affected by TET treatment and the latter system could contribute to the formation of multidrug-resistant strains. The results demonstrate that LeLac12 is an efficient and environmentally method for the removal of antibiotics and dyes in the complex polluted wastewater.

Tetracycline and sulfadiazine toxicity in human liver cells Huh-7

As typical antibiotics, tetracycline (TC) and sulfadiazine (SDZ) enter the human body through the food chain. Therefore, it is necessary to understand their individual and combined toxicity. In this study, the effects of TC, SDZ, and their mixture on cell viability, cell membrane damage, liver cell damage, and oxidative damage were evaluated in in vitro assays with human liver cells Huh-7. The results showed cytotoxicity of TC, SDZ, and their mixture, which induced oxidative stress and caused membrane and cell damage. The effect of antibiotics on Huh-7 cells increased with increasing concentration, except for lactate dehydrogenase (LDH) activity that commonly showed a threshold concentration response and cell viability, which commonly showed a biphasic trend, suggesting the possibility of hormetic responses where proper doses are included. The toxicity of TC was commonly higher than that of SDZ when applied at the same concentration. These findings shed light on the individual and joint effects of these major antibiotics on liver cells, providing a scientific basis for the evaluation of antibiotic toxicity and associated risks.

A novel mixture sampling strategy combining latin hypercube sampling with optimized one factor at a time method: A case study on mixtures of antibiotics and pesticides

Global sensitivity analysis in conjunction with quantitative high-throughput screening presents a novel technique for identifying the key components that induce the toxicities of mixtures. However, the mixtures currently designed with this method suffer from unequal frequency sampling, repeated mixtures, and only odd factor levels being considered. Accordingly, we use latin hypercube sampling to generate the starting points of the trajectories to achieve equal frequency sampling and non-repeated mixtures, as well as apply different one factor at a time methods for factors with odd and even levels to achieve suitability for factors with both odd and even levels. This method is called LHS-OAT. LHS-OAT was successfully applied to design 110 equal-frequency and non-repeated mixtures consisting of six antibiotics and four pesticides. It was found that four factors, roxithromycin (A5), tetracycline (A6), dichlorvos (P1), and demeton-S (P3), induce the toxicities of mixtures, and A5 and P1 in the Shaying River Basin have risk quotients ≥ 1. Additionally, we developed the toxicity deviation ratio to correct the risk quotients of interacting mixtures for effective risk assessments. This study provides a rational and effective method for mixture design that accurately identifies the important factors that induce the toxicities of mixtures.

Thermo-activated periodate oxidation process for tetracycline degradation: Kinetics and byproducts transformation pathways

Periodate-based advanced oxidation processes have been diffusely practiced for pollutant decontamination. However, the thermo-activation of periodate process (heat/PI), an effective water pollution removal process, has been rarely discussed, and the degradation pathway of this heat/PI system requires investigation. In this work, tetracycline antibiotics were selected as the model micropollutant for the comprehensive evaluation of the heat/PI system. The heat/PI system exhibited good performance for tetracycline (TC) remediation with temperature increases. The principal reactive oxidative species in the heat/PI system was confirmed using quenching experiments and electron paramagnetic resonance experiments. Further, the potential reactive sites in the TC were identified based on the density functional theory calculation. Based on the detection results of intermediates, there was no significant difference in byproducts generated during TC degradation under various temperatures in the heat/PI system. The Toxicity Estimation Software Tool (T.E.S.T.) method was applied to calculate the individual toxicity of the byproducts. This study contributes to a comprehensive explanation of the process of the thermal activation of periodate, and in particular, it explains the source of oxidation power, the transformation of byproducts, and the toxicity of reaction systems.

Effect of polystyrene microplastics on tetracycline photoconversion under simulated sunlight: Vital role of aged polystyrene

Photoconversion of tetracycline (TC) has been widely reported. However, the effect of microplastics (MPs) on TC conversion kinetics and mechanism has rarely been discussed. In this study, we investigated the effect of (aged) MPs on TC degradation under simulated sunlight and elucidated the underlying mechanism. Our findings demonstrated that the physical and chemical properties of polystyrene (PS), such as particle size, surface groups, and morphology, were significantly altered after aging. Moreover, photoconversion efficiency of TC was suppressed with the spiking of aged PS, while virgin PS showed an opposite tendency. The photodegradation reaction for photosensitization of PS involved 1O2 and HO·. The light-screening effect of aged PS occupied predominance, weakening the direct UV-light absorption of TC and resulting in lower TC degradation efficiency. Additionally, triplet-excited state PS was generated after photon acceptance by aged PS, which could transfer energy to O2, leading to the production of 1O2. The toxicity test manifested that the direct impact of TC products on fathead minnow was ignorable, but long-term negative effects on growth deserved observation. This study enhances our understanding of the environmental fate of PS and TC under sunlight, and provides crucial reference information for better evaluating the potential risk of MPs and chemicals.

The toxic mechanism of tetracycline on root tips in hulless barley (Hordeum vulgare L. var. nudum)

Tetracycline (TC) is a commonly used antibiotic that affects various physiological processes in plants. However, its negative effects on plants remain poorly understood at the molecular level. To ascertain the TC toxicity in the roots, transcriptomic, cytological, and physiological analyses were performed to explore the molecular mechanisms of TC influencing the growth of hulless barley root. At a low concentration (1 mg/L), TC promoted root growth by upregulating the genes related to the flavonoid pathway. At high concentrations (10, 100, and 200 mg/L), TC downregulated genes related to homologous recombination in the root meristem zone and inhibited the mitosis index by 16.4%. Disruption of the DNA repair process can lead to chromosomal aberrations, resulting in a 6.8% C-mitosis rate in the most severe cases. Finally, root growth was inhibited by TC, as evidenced by a reduction in root viability, an increase in reactive oxygen species content, and an inhibition of root length. Cross-comparison of physiological and cytological characterizations and transcriptomic information revealed changes in genetic processes under TC stress. Overall, we present an early genetic strategy to study the significant influence of TC stress on roots.

Mitigating phytotoxicity of tetracycline by metal-free 8-hydroxyquinoline functionalized carbon nitride photocatalyst

Photooxidative removal of pharmaceuticals and organic dyes is an effective way to eliminate growing micropollutants. However, photooxidation often results in byproducts as secondary hazardous substances such as phytotoxins. Herein, we found that photooxidation of common antibiotic tetracycline hydrochloride (TCH) over a metal-free 8-hydroxyquinoline (8-HQ) functionalized carbon nitride (CN) photocatalyst significantly reduces the TCH phytotoxic effect. The phytotoxicity test of photocatalytic treated TCH-solution evaluated towards seed growth of Cicer arietinum plant model endowed natural root and shoot growth. This study highlights the conceptual insights in designing of metal-free photocatalyst for environmental remediation.

Nontargeted metabolomic evidence for antagonism between tetracycline and its resistance bacteria underlying their obesogenic effects on Caenorhabditis elegans

Environmental antibiotics raise serious health concerns due to their contribution to the obesity prevalence. Moreover, antibiotics promote antibiotic-resistance bacteria (ARB) which represent another emerging pollutant. However, the interaction between antibiotic and ARB in the obesogenic effects remained unexplored. In the present study, the obesogenic effects of tetracycline antibiotic (TCH) and ARB containing tetA were studied on C. elegans, and E. coli OP50 (OP50) was referred as a normal bacterial food. Results showed that TCH stimulated nematode triglyceride contents, while ARB alone had no significant influences. The combination of TCH and ARB showed less obesogenic effects than TCH alone, showing antagonism. Biochemical assays showed that the combination of TCH and ARB showed similar effects to ARB alone, and had less increases in lipid metabolism enzymes or metabolites than those of TCH or ARB alone, supporting the antagonism. In the nontargeted metabolomic analysis, TCH with ARB showed less significantly changed metabolites (SCMs) in the nematodes than TCH or ARB alone, partially explaining the antagonism. The metabolomic results also pointed out the significant involvement of amino acids, the carboxylic acids and derivatives, and also the benzene and substituted derivatives in the obesogenic effects of TCH and ARB. The findings of the present study provided a direct support for interaction between antibiotics and ARB underlying their health risks.

Chronic intake of an enriched diet with spirulina (Arthrospira maxima) alleviates the embryotoxic effects produced by realistic concentrations of tetracycline in Danio rerio

Tetracycline (TC) is one of the most consumed antibiotics worldwide. Due to its high consumption, recent studies have reported its presence in aquatic environments and have assessed its effects on fish, algae, and daphniids. However, in most of those works, authors have tested TC toxicity at concentrations higher than the ones reported in the water matrix. Herein, we aimed to assess the likely embryotoxic and oxidative damage induced by environmentally relevant concentrations of TC in embryos of Danio rerio. Moreover, we seek to determine whether or not an enriched diet with spirulina can alleviate the embryotoxic damage produced by TC. Our findings indicated that TC at concentrations of 50 to 500 ng/L induced pericardial edema, tail deformities, and absence of head and fin in embryos after 96 h of exposure. Moreover, this antibiotic prompted the death of embryos in a concentration-dependent manner. According to our integrated biomarker response index, TC induced oxidative damage on Danio rerio embryos, as star plots showed a tendency to lipoperoxidation, hydroperoxides, and protein carbonyl content. Spirulina reduced the toxicity of TC by diminishing the levels of oxidative damage biomarkers, which resulted in a decrease in the rate of death and malformed embryos. Overall, TC at concentrations of ng/L prompted oxidative stress and embryotoxicity in the early life stages of Danio rerio; nonetheless, the algae spirulina was able to reduce the severity of those effects.

Sex-dependent obesogenic effect of tetracycline on Drosophila melanogaster deteriorated by dysrhythmia

Antibiotics have been identified as obesogens contributing to the prevalence of obesity. Moreover, their environmental toxicity shows sex dependence, which might also explain the sex-dependent obesity observed. Yet, the direct evidence for such a connection and the underlying mechanisms remain to be explored. In this study, the effects of tetracycline, which is a representative antibiotic found in both environmental and food samples, on Drosophila melanogaster were studied with consideration of both sex and circadian rhythms (represented by the eclosion rhythm). Results showed that in morning-eclosed adults, tetracycline significantly stimulated the body weight of females (AM females) at 0.1, 1.0, 10.0 and 100.0 µg/L, while tetracycline only stimulated the body weight of males (AM males) at 1.0 µg/L. In the afternoon-eclosed adults, tetracycline significantly stimulated the body weight of females (PM females) at 0.1, 1.0 and 100.0 µg/L, while it showed more significant stimulation in males (PM males) at all concentrations. Notably, the stimulation levels were the greatest in PM males among all the adults. The results showed the clear sex dependence of the obesogenic effects, which was diminished by dysrhythmia. Further biochemical assays and clustering analysis suggested that the sex- and rhythm-dependent obesogenic effects resulted from the bias toward lipogenesis against lipolysis. Moreover, they were closely related to the preference for the energy storage forms of lactate and glucose and also to the presence of excessive insulin, with the involvement of glucolipid metabolism. Such relationships indicated potential bridges between the obesogenic effects of pollutants and other diseases, e.g., cancer and diabetes.

Photocatalysis Combined with Microalgae to Promote the Degradation and Detoxification of Tetracycline Hydrochloride

The continuous discharge of antibiotics into the environment poses a serious threat to the ecological environment and human health. In this study, photocatalysis and microalgae were combined to study the removal of tetracycline hydrochloride (TCH) and its photodegradation intermediates in water. The results showed that after photocatalytic treatment, the removal rate of TCH reached 80%, but the mineralization rate was only 17.7%. While Chlorella sp. alone had poor tolerance to high concentrations of TCH, the combined treatment of photocatalysis and microalgae completely removed TCH and increased the mineralization efficiency to 35.0%. Increased cell density was observed, indicating that TCH and the intermediates produced in the photocatalysis process could be utilized by algae for growth. Meanwhile, TCH degradation pathways were proposed based on Liquid Chromatograph Mass Spectrometer analysis, and the toxicity of intermediates detected was predicted using ECOSAR software, which showed that the type and quantity of highly toxic intermediates decreased significantly after subsequent algal treatment. The results demonstrate that photocatalysis and microalgae combined treatment is an efficient and eco-friendly method for the removal of antibiotics in water.

Network analysis reveals significant joint effects of microplastics and tetracycline on the gut than the gill microbiome of marine medaka

Microplastics could accumulate and enrich antibiotics in the aquatic environment. Despite this, the joint effects of microplastics and antibiotics on aquatic organisms are not clear. Here, we investigated the changes of microbial interactions in both gill and gut of marine medaka exposed to polystyrene microbeads (PS) and/or tetracycline for 30 days by using co-occurrence network analysis based on 16S rRNA gene amplicon sequences. We found that the single and combined effects of PS and tetracycline were more profound on the gut than on the gill microbiome. SourceTracker analysis showed that the relative contributions from the gill microbiome to the gut microbiome increased under combined exposure. Moreover, the combined exposure reduced the complexity and stability of the gut microbial network more than those induced by any single exposure, suggesting the synergistic effects of PS and tetracycline on the gut microbiome. The PS and tetracycline combined exposure also caused a shift in the keystone taxa of the gut microbial network. However, no similar pattern was found for gill microbial networks. Furthermore, single and combined exposure to PS and/or tetracycline altered the associations between the gut network taxa and indicator liver metabolites. Altogether, these findings enhanced our understanding of the hazards of the co-occurring environmental microplastics and antibiotics to the fish commensal microbiome.

Degradation of tetracycline by UV/Fe3+/persulfate process: Kinetics, mechanism, DBPs yield, toxicity evaluation and bacterial community analysis

As a widely produced and used antibiotic, tetracycline (TC) has been frequently found in rivers, soil and drinking water. In this study, the degradation of TC was investigated by UV/Fe³⁺/persulfate (PS) coupled process. The degradation behavior was well fitted with pseudo-first-order model. Hydroxyl radicals (·OH), sulfate radicals (SO₄^-·) and superoxide radical (O₂^-·) were identified as the primary reactive oxygen species (ROS) in UV/Fe³⁺/PS process, the contribution to TC degradation were found to be 41.94%, 33.94% and 17.44% at pH 3.0, respectively. Fe(IV) generated from the system also played a crucial role in TC removal. The effects of process parameters (PS/Fe³⁺ dosages, pH, humic acid, Cl^-, HCO₃^-, NO₃^- and CO₃^2-) on degradation were investigated. It was found that the degradation of TC was highly pH-dependent, and the optimal performance was obtained at pH 3.0. Except for Cl^-, the presence of HA, HCO₃^-, NO₃^- and CO₃^2- inhibited TC degradation. The possible transformation pathway involving the hydroxylation, N-demethylation, hydrogenation and dehydroxylation was proposed. Furthermore, the toxicity and mutagenicity of TC and transformation products (TPs) were estimated using ECOSAR and TEST softwares, demonstrating that the toxicity level of most TPs was lower/equal to their precursors. The evaluation of DBPs showed that UV/Fe³⁺/PS process could reduce the potential of DBPs formation, especially for TCAA and TCM. Microbial community composition was analyzed by 16 S rDNA sequencing, and the relative abundance of ARG-carrying opportunistic pathogens was significantly declined after UV/Fe³⁺/PS treatment. In general, this study provides an economical, efficient and safe strategy for TC removal.

Photocatalytic degradation of tetracycline using hybrid Ag/Ag2S@BiOI nanowires: Degradation mechanism and toxicity evaluation

The wide use of antibiotics has caused their continual release and persistence in the eco-system, subsequently giving birth to antibiotic resistant bacterial species in the aquatic environment, thereby necessitating immediate and efficient remediation of the contaminated environment. In the present study, we synthesized Ag/Ag₂S@BiOI nanowires with an average diameter of ∼150 nm and length of 3-5 μm using a hydrothermal method and employed them as photocatalysts for photocatalytic degradation of tetracycline as a model antibiotic. The nanowire achieved nearly complete degradation of tetracycline (∼99%) within 60 min at the optimal condition of 100 mg/L TC concentration and pH 2. The degradation followed pseudo-first order kinetics, with a rate constant of 0.06228 min^{- 1}. Our toxicity tests showed that the nanowire has negligible toxicity towards PBMC cells, suggesting it as a promising photocatalyst.

Multi-omics analysis reveals the influence of tetracycline on the growth of ryegrass root

Environmental factors, including antibiotics such as tetracycline, can alter biological processes in plants. To ascertain how cell/tissue response to tetracycline, a multi-omic analysis was implemented to explore the molecular mechanism of tetracycline influencing the growth of ryegrass root. Tetracycline induced extensive changes in the root metabolome in plants, particularly impacting metabolites of flavonoid metabolic pathways, which were supported through consistent differences between transcriptome and proteome. Cross-comparison between mRNA and protein contents considered the authentication of congruence with related metabolites and revealed changes of several biological processes under tetracycline stress. Overall, we present an undemanding multi-omic strategy to survey the significant influence on the root under tetracycline stress.

The Role of Grass Compost and Zea Mays in Alleviating Toxic Effects of Tetracycline on the Soil Bacteria Community

Given their common use for disease treatment in humans, and particularly in animals, antibiotics pose an exceptionally serious threat to the soil environment. This study aimed to determine the response of soil bacteria and oxidoreductases to a tetracycline (Tc) contamination, and to establish the usability of grass compost (G) and Zea mays (Zm) in mitigating adverse Tc effects on selected microbial properties of the soil. The scope of microbiological analyses included determinations of bacteria with the conventional culture method and new-generation sequencing method (NGS). Activities of soil dehydrogenases and catalase were determined as well. Tc was found to reduce counts of organotrophic bacteria and actinobacteria in the soils as well as the activity of soil oxidoreductases. Soil fertilization with grass compost (G) and Zea mays (Zm) cultivation was found to alleviate the adverse effects of tetracycline on the mentioned group of bacteria and activity of oxidoreductases. The metagenomic analysis demonstrated that the bacteria belonging to Acidiobacteria and Proteobacteria phyla were found to prevail in the soil samples. The study results recommend soil fertilization with G and Zm cultivation as successful measures in the bioremediation of tetracycline-contaminated soils and indicate the usability of the so-called core bacteria in the bioaugmentation of such soils.

Degradation of tetracycline by atmospheric-pressure non-thermal plasma: Enhanced performance, degradation mechanism, and toxicity evaluation

Tetracycline is a common antibiotic and is often carelessly released into the natural environment, thus constantly posing potential threats to the environment. Currently, due to lack of effective methods to remove it from the environmental water system, researchers are still exploring new ways to deal with tetracycline. In this work, we employed atmospheric-pressure non-thermal plasma (NTP) to treat tetracycline in water and investigated the involved degradation mechanism. The enhanced degradation efficiency was acquired and investigated, and the degradation mechanism by the plasma-generated active species were explored. The tetracycline degradation pathways via especially the interactions with plasma-generated hydroxyl radical and ozone were examined by virtue of UV spectroscopy, three-dimensional fluorescence spectroscopy, high performance liquid chromatography-mass spectrometry (HPLC-MS), together with the assistance of theoretical simulations. Moreover, the toxicological evaluation of NTP treatment of tetracycline was also provided, which confirmed that the biological toxicity of tetracycline degradation products was negligible. Therefore, this work provides not only the effective way of treating antibiotics by engineered plasma technology, but also the insights into the mechanisms of degradation of antibiotics by NTP.

Removal of tetracycline from livestock wastewater by positive single pulse current electrocoagulation: Mechanism, toxicity assessment and cost evaluation

The widespread use of veterinary antibiotics has led to the significant problem of contamination of livestock wastewater with significant amount of antibiotics. Electrocoagulation (EC) has become a prominent research topic because of the technique's ability to remove antibiotics from livestock wastewater. However, an urgent solution is needed to reduce the high operating costs associated with the process. Therefore, in this study, we developed a positive single pulse current (PSPC)-EC system to remove tetracycline (TC) from synthetic and actual livestock wastewater. Influential factors were investigated, and the optimal PSPC-EC operating parameters were identified as follows: duty ratio = 60%, pH = 4, electrode spacing = 1 cm, current intensity = 0.2 A, and conductivity = 2 mS cm^-1. The mechanism of PSPC-EC was characterised using techniques including scanning electron microscopy, X-ray diffraction and Fourier transform infrared spectroscopy. The TC decomposition pathway was proposed based on the generation of its intermediate products. A toxicity estimation software tool (TEST) model was used to evaluate the toxicity of TC and its main degradation products, and most of its intermediates were found to be less toxic than TC. The contribution ratios of floc adsorption and electrochemical oxidation for removing TC were 74.17% and 21.48%, respectively. The highest TC removal rate reached 95% with an operating cost of 0.011 USD/m³. Finally, under the optimum conditions identified, actual livestock wastewater was treated by PSPC-EC. Compared with conventional EC and coagulation treatment techniques that consume electricity and produce pollution, the results indicate that the PSPC-EC technique with changing current operation mode is a more cost-effective and attractive option for removing TC from livestock wastewater.

Time-course evolution of bacterial community tolerance to tetracycline antibiotics in agricultural soils: A laboratory experiment

The presence of antibiotics in soils may increase the selection pressure on soil bacterial communities and cause tolerance to these pollutants. The temporal evolution of bacterial community tolerance to different concentrations of tetracycline (TC), oxytetracycline (OTC) and chlortetracycline (CTC) was evaluated in two soils. The results showed an increase of soil bacterial community tolerance to TC, CTC and OTC only in samples polluted with the highest antibiotic concentrations tested (2000 mg kg^-1). The magnitude of those increases was higher in the soil with the lower organic carbon content (1.6%) than in the soil with an organic carbon content reaching 3.4%. In the soil with low organic carbon content, the time-course evolution showed a maximum increase in the tolerance of bacterial communities to tetracycline antibiotics between 45 and 100 incubation days, while for longer incubation times (360 days) the tolerance decreased. In the soil with high organic carbon content, a similar behavior was found for OTC. However, for CTC and TC, slightly increases and decreases (respectively) were found in the bacterial community tolerance at intermediate incubation times, followed by values close to zero for TC after 360 days of incubation, while for CTC they remained higher than in the control. In conclusion, soil pollution due to tetracyclines may cause bacterial community tolerance to these antibiotics when present at high concentrations. In addition, the risk is higher in soils with low organic matter content, and it decreases with time.

Unveiling the visible-light-driven photodegradation pathway and products toxicity of tetracycline in the system of Pt/BiVO4 nanosheets

The antibiotics pollution has currently captured increasing concerns due to its potential hazards to the environment and human health. The development of efficient and viable techniques for the removal of antibiotics is one of the research hotspots in fields of wastewater treatment and pharmaceutical industry. Although the photodegradation of antibiotics is widely studied, the evolution and toxicity of degradation intermediates have been rarely documented. Herein, Pt nanoparticles (NPs) decorated BiVO₄ nanosheets (Pt/BiVO₄ NSs) that exhibit excellent tetracycline (TC) photodegradation activity and stability have been prepared. Especially, the TC degradation efficiency reaches ca. 88.5% after 60 min under visible light irradiation, which is superior to most of the metal loaded two-dimensional photocatalysts reported hitherto. The excellent photocatalytic activity is attributable to the enhanced light absorption capacity and charge separation efficiency in Pt/BiVO₄ NSs. h⁺, •O₂^- and •OH are the main active species for TC degradation, resulting in three possible degradation pathways. Furthermore, we first verify that TC solutions treated by Pt/BiVO₄ NSs are harmless to Escherichia coli K-12 and various bacteria in natural rivers, which would not stimulate Escherichia coli to produce antibiotics resistance genes (ARGs). This work develops an environmentally friendly photodegradation strategy using Pt/BiVO₄ NSs with potentials for efficient remediation of antibiotics pollution in wastewater.

Evolution of the earthworm (Eisenia fetida) microbial community in vitro and in vivo under tetracycline stress

Bioremediation of contaminated soil has received increasing attention, and the effects of antibiotic residues on the soil ecological environment are a current research hotspot. Earthworms are the first choice of soil organisms to indicate the degree of soil pollution, and their detoxification mechanism after antibiotic stress must be further explored. Taking Eisenia fetida as the research object, an antibiotic (tetracycline) stress test was carried out in sterile artificial soil. The stress concentrations were set at 0, 0.3, 3, 30, 300 and 600 mg/kg. The ECO method was used to cultivate microbes in earthworms and soil. The carbon source utilization intensity algorithm developed by our team was used for data statistics, and a factor analysis model was constructed to explore the succession process of microbes of earthworms in vivo and in vitro under tetracycline stress. The results showed that there were four processes in the evolution of microbes under short-term tetracycline stress: at 1-3 days, the microbes in worms played a leading role; at 4-5 days, the microbes in the worms and the soil microbes jointly resisted TET stress; after 6-8 days of stress, the microbes in worms still played the main role, but their role was weakened; and after 9-10 days, soil microbes played a leading role, and tolerant microbes appeared. Under long-term stress, the microbes of earthworms in vivo and in vitro were obvious different, and there may be no regulatory relationship. And the factor analysis model is suitable for the analyse of the changes in microbial communities in vivo and in vitro under TET stress. The research results provide a reference method and model basis for the bioremediation of antibiotic-contaminated soil and the study of earthworm detoxification mechanisms, and help agricultural development.

Hydrolytic transformation mechanism of tetracycline antibiotics: Reaction kinetics, products identification and determination in WWTPs

Antibiotic residues and antibiotic resistance have been widely reported in aquatic environments. Hydrolysis of antibiotics is one of the important environmental processes. Here we investigated the hydrolytic transformation of four tetracycline antibiotics i.e. tetracycline (TC), chlortetracycline (CTC), oxytetracycline (OTC) and doxycycline (DC) under different environmental conditions, and determined their parents and transformation products in the wastewater treatment plants (WWTPs). The results showed that the hydrolysis of the four tetracyclines followed first-order reaction kinetics, and the acid-catalyzed hydrolysis rates were significantly lower than the base-catalyzed and neutral pH hydrolysis rates. The effect of temperature on tetracycline hydrolysis was quantified by Arrhenius equation, with Ea values ranged from 42.0 kJ mol^-1 to 77.0 kJ mol^-1 at pH 7.0. In total, nine, six, eight and nine transformation products at three different pH conditions were identified for TC, CTC, OTC and DC, respectively. The main hydrolysis pathways involved the epimerization/isomerization, and dehydration. According to the mass balance analysis, 4-epi-tetracycline and iso-chlortetracycline were the main hydrolytic products for TC and CTC, respectively. The 2 tetracyclines and 4 hydrolysis products were found in the sludge samples in two WWTPs, with concentrations from 15.8 ng/g to 1418 ng/g. Preliminary toxicity evaluation for the tetracyclines and their hydrolysis products showed that some hydrolysis products had higher predicted toxicity than their parent compounds. These results suggest that the hydrolysis products of tetracycline antibiotics should also be included in environmental monitoring and risk assessment.

Enhanced removal of sulfamethoxazole and tetracycline in bioretention cells amended with activated carbon and zero-valent iron: System performance and microbial community

Antibiotics, heavily used as medicine, enter the environment inevitably and raise concerns of the risk to the ecosystems. In this study, we explored the removal efficiency and mechanism of sulfamethoxazole (SMX) and tetracycline (TC) in activated carbon (AC) and AC-zero-valent iron amended bioretention cells (AC-BRC and AC-Fe-BRC) compared with a conventional bioretention cell (BRC). Moreover, the system performance of BRCs, the shifts of the microbial community, as well as the fate of corresponding antibiotic resistance genes (ARGs) were comprehensively investigated. The results showed that, exposed to antibiotics notwithstanding, AC-BRC and AC-Fe-BRC significantly outperformed BRC on total nitrogen (TN) removal (BRC: 70.36 ± 13.61%; AC-BRC: 91.43 ± 6.41%; AC-Fe-BRC: 83.44 ± 12.13%). Greater than 97% of the total phosphorous (TP) was removed in AC-Fe-BRC, remaining unimpacted despite of the selective pressure from SMX/TC. Excellent removals of antibiotics (above 99%) were achieved in AC-BRC and AC-Fe-BRC regardless of the types and initial concentrations (0.8 mg/L, 1.2 mg/L and 1.6 mg/L) of antibiotics, dwarfing the removal performance of BRC (12.2 ± 4.4%-64.2 ± 5.5%). The illumina high throughput sequencing analysis demonstrated the concomitant variations of microbial communities as SMX/TC was loaded. AC layers tended to alleviate the adverse effect of SMX/TC on microbial biodiversity. Proteobacteria (34.55-68.47%), Chloroflexi (7.13-33.54%), and Bacteroidetes (6.20-21.03%) were the top three dominant phyla in the anaerobic zone of the BRCs. The abundance of antibiotic resistance genes (ARGs) sulI, sulII and tetA genes were dramatically higher in AC-BRC and AC-Fe-BRC when exposed to 0.8 mg/L SMX/TC, which indicated that relatively low concentrations of SMX/TC induced the production of these three ARGs in the presence of AC. Although the amendment of AC led to highly efficient SMX/TC removals, further investigation is still required to improve the retention of ARGs in BRCs.

Effects of coexistence of tetracycline, copper and microplastics on the fate of antibiotic resistance genes in manured soil

The coexistence of antibiotics, heavy metals and microplastics is becoming commonplace and may affect antibiotic resistance in manured soil. The current understanding of the role of microplastics in soil with combined pollution of antibiotics, heavy metals and antibiotic resistance genes (ARGs) is limited. Here, the effects of the coexistence of tetracycline (TC), Cu and environmental microplastics (EM) on the fate of nine ARGs and three heavy metal resistance genes in agricultural soil were investigated by batch and microcosm experiments. EM were obtained by exposing virgin microplastics to soil environments for 80 days, which exhibited higher adsorption affinity for Cu and TC than soil particles and virgin microplastics. 1% EM in soil increased bioavailable concentrations of TC and Cu by 79-138% and 88-135%, respectively, and decreased TC dissipation from 11.79 mg kg^-1 to 3.08 mg kg^-1. Correspondingly, the total relative abundances of target ARGs increased by 219-348%. The significant correlations of tetG, tetB, tetQ, sul2, sul1 and intl1 with bioavailable fractions of TC and Cu in soil environments were revealed by network analysis. Moreover, scanning electron micrographs showed the special plastisphere around EM. Attributed to the biofilm generation and higher pollutant accumulation in the plastisphere, EM could be the source of antibiotic-resistant bacteria and ARGs in soil environments. Structure equation models further identified that indirect effects of EM acted a major role in the propagation of ARGs by altering soil properties, soil microbial diversity and intl1 abundance. This study revealed that EM could increase the stimulative effects of Cu and TC on antibiotic resistance and magnify the environmental risk of manure application in soil environments.

Recovery of gut microbiota in mice exposed to tetracycline hydrochloride and their correlation with host metabolism

Antibiotics can disturb the gut microbial community and host metabolism. However, their recovery after antibiotics exposure needs to be characterized, and the correlation between gut microbiota and host metabolism remains unclear. In this study, mice were exposed to 0.5, 1.5 and 10 g/L tetracycline hydrochloride (TET) for 2 weeks, then recovered without TET for another 2 weeks. The results showed that 2-week TET exposure changed microbial community and functions in the mouse gut, and increased abundance of antibiotic resistance genes (ARGs), especially in the 10 g/L TET group. After a 2-week recovery, these changes could only be recovered to the control level in the 0.5 g/L TET exposure group, except for ARGs. Besides gut microbiota, TET exposure also changed metabolic profiles in mouse urine. The 2-week recovery significantly reduced changes in metabolic profiles. Some altered metabolites were found to have a very high correlation with gut microbial community and functions, indicating that TET exposure might induce certain changes in urinary metabolic profiles by altering the gut microbiota. The results from this study suggest that the influences of low-level TET exposure are reversible, except for ARGs, which should be paid more attention. During the application of TET, their dosage should be effectively considered and controlled.

Estimating the synergistic and antagonistic effects of dual antibiotics on plants through root elongation test

Antibiotics are recently recognized as a group of emerging environmental contaminants that are frequently detected in various environmental matrixes. Relative root elongation (RRE) test is a rapid and effective strategy to evaluate the water/soil quality and the toxic effects of environmental contaminants on plants. In the present study, we examine the toxicity effect of ciprofloxacin (CIP), norfloxacin (NOR), and tetracycline (TET) to pakchoi individually and in combinations. Both independent action (IA) and concentration addition (CA) models are used for toxicity assessment. Results showed that the EC₅₀ values of CIP, NOR, and TET are 193.59, 60.81, and 40.37 μM, respectively. Combinations of TET + CIP and TET + NOR caused more inhibitory effects on root elongation than those of CIP + NOR. Toxic Unit (TU) and Synergistic Ratio (SR) analysis showed that the relatively lower (higher) EC values are observed in the combinations with lower (higher) antibiotic concentrations, suggesting an effect of low-dose synergism and high-dose antagonism. The reliability of the simulation results from IA and CA models to predict that combined toxicity is highly dependent upon the results from the analysis of TU or SR.

Comparative study of cefixime and tetracycline as an evaluation policy driven by the antibiotic resistance crisis in Indonesia

Antibiotic resistance is a serious threat that occurs globally in the health sector due to increased consumption of inappropriate antibiotics. Guidelines for prescribing antibiotics for ARTIs have been issued in general practice to promote rational antibiotic prescribing. This study was conducted to compare the effectiveness of cefixime and tetracycline as a solution to improve monitoring of appropriate antibiotic use in the treatment of ARTIs. All stock isolates were rejuvenated first, and cultured on standard media and Kirby-Bauer disc diffusion method was used for susceptibility testing in accordance with the Clinical and Laboratory Standard Institute's (CLSI) recommendations. Identification of bacteria from a single isolate was carried out to determine which bacteria were resistant to cefixime and tetracycline. A total of 466 single isolates of bacteria were analyzed, which showed a percentage of resistance to cefixime 38.0%, and tetracycline 92.86%. Bacterial isolates were resistant to cefixime and tetracycilne was a genus of Haemophilus, Streptococcus, Corynebacterium, Staphylococcus, and bordetella. Cefixime compared to tetracycline was proven to be superior in terms of the effectiveness of ARIs treatment.

Feeding state greatly modulates the effect of xenobiotics on gut microbiome metabolism: A case study of tetracycline

The human gut microbiome is crucial in modulating host health mostly through bacterial metabolites. Chemical exposure is typical external stress which alters its composition and functionality. To date, very few studies have investigated the effect of feeding state on chemical-induced gut microbial metabolic dysregulations. Here, we set up an in vitro human gut microbiome and incorporated a metabolomics approach to investigate the effect of tetracycline (TET) at multiple doses (i.e., 10, 1, and 0.01 mg/L) on gut microbiome under the fed and fasted states. Overall, the metabolome was highly responsive at the fed state with 62 metabolites dysregulated while only 14 were altered at the fasted state under 10 mg/L (clinical TET dose). As expected, nutrient consumption was significantly inhibited under clinical TET dose at the fed state accumulating nutrients such as glutamate and leucine. Interestingly, at the fed state, TET could increase the synthesis of indole and phenyl derivatives including indole-3-aldehyde and hydrocinnamate, while inhibiting indoxyl, tryptamine, and vitamin B production, all of which have host health implications. Furthermore, metabolites like indoxyl and xanthurenic acid were still responsive at 0.01 mg/L (dietary TET dose). Collectively, results demonstrated that the feeding state greatly modulates the chemical-induced gut microbial metabolic alterations.

Tetracycline-induced decoupling of symbiosis in microalgal-bacterial granular sludge

Tetracycline has been frequently detected in municipal wastewater due to its extended use for various purposes. This study investigated the influence of tetracycline on non-aerated microalgal-bacterial granular sludge cultivated for municipal wastewater treatment. It was found that ammonia-N removal rate decreased at the tetracycline concentrations of 1 and 10 mg/L. A mass balance on nitrogen further revealed that the observed ammonia-N removal could be mainly attributed to microalgal assimilation which was inhibited by tetracycline at the concentrations studied. In fact, reduced production of chlorophyll in microalgae was observed in the presence of tetracycline, leading to decreased ammonia-N removal rate. Meanwhile, decreased dissolved oxygen (DO) concentration at high tetracycline concentration also indicated inhibition of microalgae. Furthermore, the relative abundances of microalgae containing green algae and cyanobacteria were inhibited by tetracycline. The results gathered in this study indicated the tetracycline-induced decoupling of symbiosis in microalgal-bacterial granular sludge. It is expected that this study can shed lights on the behaviors of non-aerated microalgal-bacterial granules in response to the presence of tetracycline during municipal wastewater treatment.

Providing a view for toxicity mechanism of tetracycline by analysis of the connections between metabolites and biologic endpoints of wheat

Metabolomics is an implement for testing the toxicity of antibiotics, and provides a comprehensive view of the overall response to stress; however, the connections between metabolites and biologic endpoints keep unclear in response to antibiotics. In this study, wheat seeds were exposed to tetracycline for 5 days. The results proved that tetracycline restrained growth, reduced chlorophyl and carotinoid contents and cell permeability, and increased reactive oxygen species (ROS) levels and malondialdehyde (MDA) content. Orthogonal partial least squares (OPLS) was used to analyze the connections between metabolites and biologic endpoints, which discovered that 11 metabolic pathways were significantly affected by tetracycline, and amino acid metabolism could largely apply to root growth and ROS accumulation, while carbohydrate metabolism could have a ruling effect on tetracycline-induced cell permeability. 13 metabolites all played active roles in mediating tetracycline's effects on root length, root fresh weight and cell permeability but had no significant effects on ROS levels. The majority of metabolites with passive effects on root length, root fresh weight and cell permeability had active effects on ROS levels. These results offer a view about stress reaction of wheat to tetracycline.

Interaction between tetracycline and microorganisms during wastewater treatment: A review

Tetracycline (TC) is a commonly used human and veterinary antibiotic that is mostly discharged into wastewater in the form of the parent compounds. At present, wastewater treatment plants (WWTPs) use activated sludge processes that are not specifically designed to remove such pollutants. Considering the biological toxicity of TC in aquatic environment, the migration and fate of TC in the process of wastewater treatment deserve attention. This paper reviews the influence of TC on the functional bacteria in the sludge matrix and the development of tetracycline-resistant genes, and also discusses their adsorption removal rates, their adsorption kinetics and adsorption isotherm models, and infers their adsorption mechanism. In addition, the biodegradation of TC in the process of biological treatment is reviewed. Co-metabolism and the role of dominant bacteria in the degradation process are described, along with the formation of degradation byproducts and their toxicity. Furthermore, the current popular integrated coupling-system for TC degradation is also introduced. This paper systematically introduces the interaction between TC and activated sludge in WWTPs. The review concludes by providing directions to address research and knowledge gaps in TC removal from wastewater.

Responses of Hydrocharis dubia (Bl.) Backer and Trapa bispinosa roxb. to tetracycline exposure

The presence of tetracycline is ubiquitous and has adverse effects on aquatic systems. A hydroponic experiment was conducted to investigate the ecological sensitivity of Hydrocharis dubia (Bl.) Backer and Trapa bispinosa Roxb. Exposed to different concentrations of tetracycline (0, 0.1, 1, 10, 30 and 50 mg/L) for one day (1D) and 14 days (14D). The results showed that after 1D of tetracycline exposure, the physiological indices of H. dubia had no remarkable change except for proline which was significantly stimulated under 0.1 mg/L tetracycline. For T. bispinosa, guaiacol peroxidase (POD), polyphenol oxidase (PPO) and ascorbate peroxidase (APX) activity and protein and proline content were notably promoted under different concentrations of tetracycline, but PPO activity was significantly decreased in 50 mg/L. After 14D, tetracycline caused no harm to the growth and protein content of H. dubia, but negatively influenced lipid peroxidation product and chlorophyll content in H. dubia under high tetracycline concentrations. Superoxide dismutase (SOD) and POD activity of H. dubia significantly increased at high tetracycline concentrations, while catalase (CAT) and PPO activity significantly decreased. APX activity in H. dubia increased with tetracycline concentrations at low tetracycline concentrations. For T. bispinosa, high concentrations of tetracycline application significantly inhibited its growth and the content of protein and chlorophyll. SOD, POD, CAT, and PPO activity of T. bispinosa were induced under different concentrations of tetracycline and no lipid peroxidation was observed. APX activity in T. bispinosa was significantly inhibited at high tetracycline concentrations. The results suggest that tetracycline can cause oxidative damage in H. dubia but harm the metabolism process of T. bispinosa without inducing oxidative damage. Overall, the sensitivity of T. bispinosa exposed to tetracycline exposure is higher than that of H. dubia.

Toxicity of two tetracycline antibiotics on Stentor coeruleus and Stylonychia lemnae: Potential use as toxicity indicator

The environmental toxicity of tetracycline antibiotics to aquatic organisms has attracted increasing attention. The adverse impacts of tetracycline antibiotics on ciliates should be detailed considering the significant roles of protozoa in the microfood web in the soils and other eco-systems. This study for the first time investigated the toxicity of two typical tetracycline antibiotics, tetracycline (TC) and tetracycline hydrochloride (HTC) on two primary model ciliates, Stentor coeruleus and Stylonychia lemnae. The concentrations for 50% of maximal effect (24h‒EC₅₀) of TC and HTC to Stentor coeruleus were 94.4 mg/L and 8.39 mg/L, respectively. Correspondingly, the 24h‒EC₅₀ values of TC and HTC to Stylonychia lemnae were 40.1 mg/L and 14.0 mg/L, respectively. The TC and HTC inhibited the growth rates, reduced the activities of antioxidant enzymes, and damaged the ultra-structures of the tested ciliate cells, with the latter having larger impacts than the former. Based on the experimental works reported herein, the two model protozoan species were proposed to be the toxicity indicators for tetracycline antibiotics, which could work as supplements with the other existing protocols, such as Brochydanio rerio (zebrafish), Limnodrilus (a worm), Chlorogonium elongatum (a green alga) also studied herein.

Design and synthesis of robust Z-scheme ZnS-SnS2 n-n heterojunctions for highly efficient degradation of pharmaceutical pollutants: Performance, valence/conduction band offset photocatalytic mechanisms and toxicity evaluation

Petal-like ZnS-SnS₂ heterojunctions with Z-scheme band alignment were prepared by one-pot solvothermal strategy. The optimal (1:1) ZnS-SnS₂ can degrade 93.46 % of tetracycline and remove 73.9 % COD of pharmaceutical wastewater under visible-light irradiation due to the efficient production of H, O₂^-, h⁺ and OH. The toxicity evaluation by ECOSAR prediction and the growth of E. coli indicates efficient toxicity reduction of tetracycline by photocatalysis and the non-toxicity of ZnS-SnS₂. The attacked sites on tetracycline by reactive species were analyzed according to Fukui index, and two degradation pathways of tetracycline were inferred via the identification of intermediate products. Tetracycline degradation efficiency and the energy consumption in different water bodies were compared, and it was found that the electrical energy per order (EE/O) was the lowest in Ganjiang River. The valence band offset (ΔE_VBO) and conduction band offset (ΔE_CBO) of ZnS-SnS₂ were 1.02 eV and 0.22 eV, respectively. The probable photocatalytic mechanism of ZnS/SnS₂ heterojunctions with Z-scheme band alignment based on ΔE_VBO and ΔE_CBO was first presented.

Effects of tetracycline on the relationship between the microbial community and oxidative stress in earthworms based on canonical correlation analysis

In this study, Eisenia fetida was taken as the test organism and tetracycline was taken as the stress compound. The artificial soil test was conducted to study the utilization intensity of different carbon sources (the Biolog-microplate supplied) by microorganisms under different stress times and stress concentrations. The changes in the in vivo key enzymes activities of earthworms and oxidative stress indicators, such as malondialdehyde (MDA), were explored. The canonical correlation analysis method was the first used to establish a analysis-model to explore the relationship between the functional diversity of microbial community and the oxidative stress in earthworms in vivo under different stress times and concentrations. Research shows: 1) after tetracycline stress, in the earthworm, the CAT, POD, SOD, GPX were related to the microbes that use carbohydrate carbon sources; the GST and AChE were related to the microbes that use polymer carbon sources; the MDA was related to the microbes that use carbon sources: amino acid, carboxylic acid and phenolic acid. 2) Under low concentrations of tetracycline stress, there was no significant relationship between the functional diversity of the microbial communities and the effects of oxidative stress at this concentration. The high concentration of tetracycline can be utilized to screen probiotics that alleviate the effects of oxidative stress. 3) The utilization of carbon sources by microbial community in the earthworm after stress can be used as biomarker of ecotoxicology. It provides a basic theoretical for adding beneficial carbon sources to combat oxidative damage in vivo.

Toxicity of tetracycline and its transformation products to a phosphorus removing Shewanella strain

Tetracycline (TC) as an emerging contaminant has raised serious concerns about its toxicity and removal in wastewater treatment processes. The more toxic transformation products of TC, 4-epitetracycline (ETC), anhydrotetracycline (ATC) and 4-epianhydrotetracycline (EATC) are also widely detected. This study investigated the antibacterial and bactericidal activity of TC, ETC, ATC, EATC against Shewanella sp, using Escherichia coli and Pseudomonas aeruginosa strains as quality controls. Further, batch assays were conducted to investigate the inhibition of these antibiotics on the phosphorus removal of the Shewanella strain, and removal mechanisms of TC and its transformation products (TCs). The inhibition on phosphorus removal by the Shewanella strain at 20 mg L^-1 was in the order of ATC > EATC > TC > ETC. COD removal, poly-P accumulation and glycogen synthesis by the Shewanella strain were also inhibited. Biodegradation was the main removal mechanism of TC and ETC, while adsorption was the main one of ATC and EATC. This study helps to further understand the structure-activity relationship of TC.

The Complex Toxicity of Tetracycline with Polystyrene Spheres on Gastric Cancer Cells

Nowadays, microplastics (MPs) exist widely in the marine. The surface has strong adsorption capacity for antibiotics in natural environments, and the cytotoxicity of complex are poorly understood. In the study, 500 nm polystyrene (PS-MPs) and 60 nm nanoplastics (PS-NPs) were synthesized. The adsorption of PS to tetracycline (TC) was studied and their toxicity to gastric cancer cells (AGS) was researched. The adsorption experimental results show that PS absorbing capacity increased with increasing TC concentrations. The defense mechanism results show that 60 nm PS-NPs, 500 nm PS-MPs and their complex induce different damage to AGS cells. Furthermore, 600 mg/L PS-NPs and PS-MPs decline cell viability, induce oxidation stress and cause apoptosis. There is more serious damage of 60 nm PS-NPs than 500 nm PS-MPs in cell viability and intracellular reactive oxygen species (ROS). DNA are also damaged by 60 nm PS-NPs and PS-TC NPs, 500 nm PS-MPs and PS-TC MPs, and 60 nm PS-NPs damage DNA more serious than 500 nm PS-MPs. Moreover, 60 nm PS-NPs and PS-TC NPs seem to promote bcl-2 associated X protein (Bax) overexpression. All treatments provided us with evidence on how PS-NPs, PS-MPs and their compounds damaged AGS cells.

Do combined nanoscale polystyrene and tetracycline impact on the incidence of resistance genes and microbial community disturbance in Enchytraeus crypticus?

It has been proved that nanoplastics can effectively adsorb pollutants and thus influence their behavior and availability. The combined toxic effects of nanoplastic and its adsorbed pollutant on the soil fauna are still not well known. We used high-throughput quantitative PCR to explore the effects of oral nanoscale polystyrene and tetracycline exposure on antibiotic resistance genes in the soil invertebrate Enchytraeus crypticus, and used bacterial 16S rRNA gene amplification sequencing to examine the response of the microbiome of E. crypticus. After 14 days of tetracycline and nanoscale polystyrene exposure, we terminated exposure and monitored the restoration of ARGs and microbiome in the E. crypticus. Results showed that the number of ARGs, especially macrolide-lincosamide-streptogramin B (MLSB), tetracycline ARGs, as well as multidrug ARGs, increased with exposure to nanoscale polystyrene and tetracycline. The abundance of Aminoglycoside and Beta_Lactamase ARGs in E. crypticus also significantly increased. The exposure significantly perturbed the abundance of families Microbacteriaceae, Streptococcaceae, Enterobacteriaceae, Rhodocyclaceae and Sphinomonadaceae. After terminating exposure for 14 days, the diversity and abundance of ARGs were not completely restored, while the microbiome was not permanently changed but reversibly impacted.

Characterization of tetracycline effects on microbial community, antibiotic resistance genes and antibiotic resistance of Aeromonas spp. in gut of goldfish Carassius auratus Linnaeus

The gut of aquatic animals was a significant niche for dissemination of antibiotic resistance genes (ARGs) and direct response of living conditions. In this study, the gut microbiota of goldfish Carassius auratus Linnaeus was sampled at 7 days and 21 days after treatment with tetracycline at 0.285 and 2.85 μg L^-1 to investigate the influences on the microbial structure and antibiotic resistance. The proportion of tetracycline resistance bacteria was 1.02% in the control group, while increased to 23.00%, 38.43%, 62.05% in groups of high concentration for 7 days (H7), low concentration for 21 days (L21) and high concentration for 21 days (H21), respectively. Compared to the control group, the diversity of isolated Aeromonas spp. was decreased in the treatment groups and the minimal inhibitory concentration (MIC) of resistant isolates was enhanced from 32 to 256 μg mL^-1 with the treatment of tetracycline in time- and dose-dependent manners. Furthermore, the abundance of most genes was increased in treatment groups and efflux genes mainly responded to the stress of tetracycline with an average level of 1.0 × 10^-2. After treatment with tetracycline, the predominant species were changed both at phylum and genus levels. The present study explored the impact of tetracycline on gut microbiota of goldfish at environmentally realistic concentrations for the first time and our findings will provide a reference for characterizing the microbiome of fish in the natural environment.

Sensitivity difference between skotomorphogenesis and photomorphogenesis of plants to antibiotics: A call for research

Seedling establishment consists of the former stage (i.e. skotomorphogenesis) and the latter stage (i.e. photomorphogenesis). Due to specific developmental processes in plants, the two stages may have different sensitivities to antibiotics. Tetracycline (TC), for example, is a major-use antibiotic. Radicle length, the relatively sensitive endpoint in plant skotomorphogenesis, is less sensitive than all of the indices of cotyledon colour and pigments in plant photomorphogenesis to TC stress. In conclusion, we suggest that plant photomorphogenesis may be more sensitive than plant skotomorphogenesis to stresses of antibiotics, but which needs further studies.

Insights into degradation pathways and toxicity changes during electro-catalytic degradation of tetracycline hydrochloride

The removal of antibiotics has attracted much attention due to their extremely high adverse impacts on the environment. However, the potential risks of degradation intermediates are seldom reported. In this work, the influence of different factors on the electro-catalytic degradation efficiency of tetracycline hydrochloride (TCH) by the prepared carbon nanotubes/agarose/indium tin oxide (CNTs/AG/ITO) electrode was investigated. Under optimal conditions (10 wt% CNTs dosage, pH = 7), the maximum degradation efficiency for TCH (10 mg L^-1) reached up to 96% within 30 min treatment with 4 V potential. Superoxide anions (•O₂^-) played an important role in the electro-catalytic degradation. Totally 10 degradation intermediates were identified using HPLC-MS/MS, and the degradation pathway was proposed. Toxicities of the parent antibiotic and the identified intermediates were calculated using the ECOSAR (Ecological Structure Activity Relationship) program in EPISuite, and results showed that more toxic intermediates were generated. The maximal chronic toxicity for green algae of the intermediate increased 1439.92 times. Furthermore, antimicrobial activity was further verified by disk agar biocidal tests with Escherichia coli ATCC25922 and higher biotoxicity intermediates compared with parent compounds were confirmed to be formed. Therefore, more attention should be paid on the potential risk of degradation intermediates in the treatment of wastewater containing antibiotics.

Embryotoxic and teratogenic profile of tretracycline at environmentally relevant concentrations on Cyprinus carpio

The objective of this work was to evaluate whether tetracycline (TC) in environmentally relevant concentrations was able to induce alterations to embryonic development and teratogenic effects in oocytes and embryos of Cyprinus carpio. For this purpose, an embryolethality study was conducted and the lethal concentration 50 (LC₅₀) and effective concentration 50 of malformations (EC₅₀) were calculated, and with these data the teratogenic index (TI) was determined. The main alterations to embryonic development and the teratogenic effects produced by TC on embryos of C. carpio were determined using the Kimmel and Hersem scale adapted for Cyprinus carpio. LC₅₀ and EC₅₀ were respectively 500.08 and 145.3 μg L^-1.TC was shown to be teratogenic with teratogenic index of 3.44, and the main malformations identified in concentrations of 90-900 μg L^-1 were malformation in tail, modified chorda structure, pericardical edema, scoliosis and malformations of the heart. A significant decrease in concentration-dependent in Kimmel and Hersem score was observed. The results allow us to conclude that TC at environmentally relevant concentrations is capable of inducing embryotoxic and teratogenic effects, generating risk in the integrity of the common carp C. Carpio.

Tetracycline-induced effects on the nitrogen transformations in sediments: Roles of adsorption behavior and bacterial activity

Nitrification and denitrification are the most important nitrogen transformation processes in the environment. Recently, due to widespread use, antibiotics have been reported to lead to environmental risks. Tetracycline (TC) is one of the most extensively used antibiotics in many areas. However, its reported effects on nitrogen transformations were conflicting in previous studies. In this study, the effects of TC on nitrogen transformations in sediment were investigated by analyzing TC transport and bacterial activity. It was found that the adsorption of TC onto the sediment was favorable and spontaneous, with adsorption capacity 54.3 mg/kg. The adsorption kinetics of TC onto the sediment and the isotherm fitted the Elvoich and Freundlich models, respectively, indicating that the adsorption was a chemisorption process, including electrostatic interactions and chemical bonding between TC and the sediment. TC showed no effect on nitrification in the sediment, but significantly inhibited the reduction of nitrate and nitrite during denitrification, consistent with observations made for the model denitrifier Paracoccus denitrificans under TC stress. Mechanistic study indicated that TC at 130 μg/g-cell inhibited 50.7% of P. denitrificans growth and 61.6% of cell viability. Meanwhile, the catalytic activities of the key denitrifying enzymes, nitrate reductase (NAR) and nitrite reductase (NIR), decreased to 29.1% and 68.0% of the control levels when the TC concentration was 130 μg/g-cell, suggesting that NAR was more sensitive to the TC than NIR, which contributed to a delay in nitrite accumulation.

Tetracycline affects the toxicity of P25 n-TiO2 towards marine microalgae Chlorella sp

Pollutants such as n-TiO₂ and tetracycline enter the marine environment through various sources starting from their production until disposal. Hence, it is vital to determine the interactive effect of one pollutant with the other when they coexist in the environment. In the present study, the effect of antibiotic - tetracycline (TC) on the toxicity of P25 n-TiO₂ was studied with marine microalgae, Chlorella sp. The impact of TC (1 mg L^-1) on five different concentrations of n-TiO₂ (0.25, 0.5, 1, 2 and 4 mg L^-1) under both visible and UV-A illuminations was evaluated. Effective diameter of n-TiO₂ in ASW at 0^th h increased from 690.69 ± 19.55 nm (0.25 mg L^-1) to 1183.04 ± 37.10 nm (0.25 mg L^-1 + 1 mg L^-1) and 971.51 ± 14.61 nm (4 mg L^-1) to 1324.12 ± 11.59 nm (4 mg L^-1 + 1 mg L^-1) in presence of TC. A significant increase in the toxicity of 4 mg L^-1 n-TiO₂ upon the addition of TC (68.16 ± 0.37% under visible and 80.21 ± 0.3% under UV-A condition) was observed. No significant difference in toxicity was observed between visible and UV-A illuminations. Further the toxicity data was corroborated through the measurement of oxidative stress and antioxidant enzyme activities. Independent action model showed antagonistic effect for lower concentrations of n-TiO₂ and additive effect for higher concentrations of n-TiO₂ when present in mixture with TC under both illuminations. For the higher mixture concentration of 4 mg L^-1 n-TiO₂ and 1 mg L^-1 TC, the percentage TC removal was about 55.29% and 30% and the corresponding TOC removal was found to be 54.29% and 31.04% under visible and UV-A illuminations respectively. The site of ROS generation in Chlorella sp. was identified with electron transfer chain inhibitors. Both mitochondria and chloroplast acted as the site for the ROS generation in Chlorella sp. The SEM images of the algal cells upon exposure to n-TiO₂ and mixture revealed the aggregation of cells and distortion of cell membrane.

Responses of seeds of typical Brassica crops to tetracycline stress: Sensitivity difference and source analysis

Antibiotics can induce adverse effects on plants. Brassica crop seeds, for their advantages, are used widely in seed germination test to investigate phytotoxicity of substances. However, their performances on evaluating antibiotics remain to be studied to select sensitive species for control of potential risks. In this work, common species of Chinese cabbage (Brassica rapa L.), edible rape (Brassica napus L.), and cabbage (Brassica oleracea L.) with three cultivars each were selected to compare and analyze the sensitivity difference of their seeds to tetracycline (TC) stress. Results showed that the ratio of axis to cotyledon (RAC) by fresh weight was an alternative endpoint besides radicle length (RL) in the test. The species sensitivity distribution (SSD) based on the effective concentrations causing x% inhibition (EC_x) in RL of seeds exposed to TC was applied to compare the sensitivity of seeds and estimate the hazardous concentration for x% species (HC_x). From the species-dependent sensitivity and the sensitivity difference of cultivars in the same species of seeds to TC, the performance of Chinese cabbage was the best in the study. The sensitivity of seeds to TC could be evaluated by EC₂₀ related to seed physical traits and germination indices, while the extent of seeds affected by TC could be evaluated by EC₅₀ related to the composition of seed storage reserves. We recommended that it was a new idea to analyze responses of different seeds to TC at large scale according to seed innate characteristics.

Direct photo transformation of tetracycline and sulfanomide group antibiotics in surface water: Kinetics, toxicity and site modeling

The direct photo-transformation of widely used antibiotics, including Tetracycline (TTC), chlortetracycline (CTC), sulfamethoxazole (SMX) and sulfamethazine (SMZ) were quantified for surface water by using artificial UV irradiation. The photolysis rate is directly proportional to the overlap between the absorption spectrum of the solution and the spectrum of the terrestrial sunlight. Increasing overlap fraction of Tetracycline (TC) group than Sulfanomide (Sulfa) group, the transformation of TC group is certified much faster than the sulfa group. The speciation of TC and Sulfa group antibiotics are pH-dependent and consequently influence its light adsorption spectrum. And the toxicity of the four target antibiotics along the photo-transformation was assessed. In field aquatic environment, a temporal- and spatial half-life model described the behavior of the antibiotics in water column of victoria harbour could be validated by using experimentally obtained quantum yield with the target field meteorological data. The modeling results indicated the photolysis rate of different kind of antibiotics varied differently along season, daily time and water depth. Summer, midday and surface layer of water body would be the time- and space-highlight spot in which the phototransformation are the dominant process for antibiotics concentration depletion. Seasonal variety would be enhanced for sulfa-group kind antibiotics, which having only tail overlapped with irradiation spectrum. Daily averaged half-lives of TC group were relatively stable, while the sulfa group antibiotics were found to vary from about 300 to 750 h, dependent on the seasonal change.

Tetracycline uptake by pak choi grown on contaminated soils and its toxicity in human liver cell line HL-7702

Tetracycline (TC) can enter the human body via the soil-vegetable-human food chain; therefore, it is necessary to understand the toxicity of TC to humans through vegetables grown on contaminated soils. The present study combined an enzyme-linked immunosorbent assay method and an HL-7702 cell model and assessed the bioavailability and toxicity of TC from pak choi (Brassica campestris L. ssp. chinensis) grown on TC-contaminated soils. The results showed that the degradation rate of TC in black soil was significantly higher than that in purplish clay, while the results for TC uptake in pak choi were opposite. The bioaccessibility of TC was found to be higher in pak choi grown on purplish clay (5.67-7.59%) than in that grown on black soil (5.22-6.77%). It is suggested that soil properties contribute to the uptake of TC by pak choi. More fertile soil contained lower TC concentrations and thus mediated lower TC toxicity to humans. It may seem comforting that TC concentrations in the edible parts of pak choi are often found to be below safe limits. However, the TC diagnosis method showed that even moderate increases in TC concentrations in pak choi may induce oxidative stress, liver injury, mitochondrial cristae and rough endoplasmic reticulum swelling, and early apoptosis in liver cells HL-7702. The pak choi grown in purplish clay showed higher TC cytotoxicity than that grown in black soil. The TC cytotoxicity of raw pak choi was found to be higher than that of cooked pak choi. These results provide direct evidence of effective ways to prevent TC toxicity in humans.

Evaluation of tetracycline phytotoxicity by seed germination stage and radicle elongation stage tests: A comparison of two typical methods for analysis

Biological tests with plant seeds have been adopted in many studies to investigate the phytotoxicity of pollutants to facilitate the control of risks and remain to be optimized. In this work, the experiment with a small sample size (Experiment 1) and the experiment with a large one (Experiment 2) were designed to study the effect of tetracycline (TC) on Chinese cabbage (Brassica rapa L.) at seed germination and radicle elongation stages. At the former stage, germination number data were obtained to analyze the germination energy (GE) and to judge the probability of the number of germinated seeds (P_n) by the binomial distribution model in Experiment 1. While germination time-to-number data were obtained to analyze the mean time to germination (MGT), the estimate of mean time to germination (EMGT) by survival analysis method, the time to germination for 50% of total seeds (T₅₀) and the germination rate (GR) besides GE in Experiment 2. At the latter stage, the data of radicle length (RL) were obtained in all the experiments and the influence from the former stage on this stage was excluded in Experiment 2 but not in Experiment 1. Results showed that TC had universal adverse effects on the latter stage but not on the former stage in the experiments. Considering the availability of germination data for statistical analysis and the robustness of RL data, the methods adopted in Experiment 2 were more feasible than those in Experiment 1. In addition, Chinese cabbage seeds with medium size have the character of rapid germination compared with the commonly used crop species and can be used to shorten the experimental cycle to study the responses of seeds to pollutants to evaluate the phytotoxicity. We introduced survival analysis method to analyze the germination time-to-number data obtained in seed germination test to evaluate the phytotoxicity of tetracycline.

Toxic effects of tetracycline and its degradation products on freshwater green algae

Tetracycline antibiotics are the most widely used antibiotics in the world and the most common veterinary drugs and feed additives used in livestock, poultry and aquaculture operations. Because antibiotics cannot be completely removed by currently existing sewage treatment facilities, these materials enter the environment directly via sewage treatment plant discharge, where they degrade. Accordingly, the metabolism and the ecological toxicity of tetracycline degradation products are worthy of attention. Herein, we investigated the effects of tetracycline and its degradation products (anhydrotetracycline and epitetracycline hydrochloride) on the growth, cell structure and algal cell oxidative stress of common Chlorella vulgaris. The results showed that the 96h-EC₅₀ values of tetracycline (TC), anhydrotetracycline (ATC) and epitetracycline (ETC) on algal cells were 7.73, 5.96 and 8.42 mg/L, respectively. Moreover, the permeability of algal cells exposed to high concentrations of these three drugs was significantly enhanced. In addition, there were structural changes in the cells such as plasmolysis and starch granule deposition appeared, the thylakoid lamellae in the chloroplasts became blurred and deformed, and the vacuoles became larger. Exposure to higher concentrations (>5 mg/L) of TC and its degradation products ATC and ETC significantly upregulated the activity of ROS, as well as the antioxidants SOD and CAT. The levels of the lipid peroxidation product MDA also showed the same trend. Finally, ATC had the strongest toxicity toward algal cells, followed by TC and then ETC.