Oxidative response of rice (Oryza sativa L.) seedlings to quinolone antibiotics and its correlation with phyllosphere microbes and antibiotic resistance genes

Ecotoxicological effects of individual and combined treatments of chlortetracycline and oxytetracycline on seed germination and seedling growth of wheat (Triticum aestivum L.)

A significant issue facing the world today is the antibiotics pollution of agroecosystems. Chlortetracycline (CTC) and oxytetracycline (OTC) are frequently detected antibiotics in soil. However, little is known about their ecotoxicological effects on crops. Here, the potential adverse effect of CTC and OTC individually and in combination on germination, growth, antioxidant enzyme, malondialdehyde (MDA), chlorophyll, and soluble protein (SP) in Triticum aestivum L. grown in soil contaminated with 1, 10, and 50 mg (CTC and/or OTC) × kg-1 of soil was tested. The results showed that low concentrations (1 mg·kg-1) of CTC, OTC, and combinations of antibiotics (CA) promoted seeds germination and root elongation, which were inhibited by high concentrations (50 mg·kg-1) of CTC or OTC. CTC and/or OTC-exposure significantly reduced plant heights, with OTC having the most pronounced effects. Biomass accumulation was not evidently influenced by CTC or OTC but was significantly increased by their mixture. Peroxidase, superoxide dismutase, catalase activity, and MDA level increased with elevated CTC and/or OTC concentrations, indicating oxidative damage to wheat. Chlorophyll, carotenoid, and SP were decreased by exposure to low concentration of CTC and/or OTC but were slightly increased with the increase in concentration. Integrated biomarker response (IBR) analysis indicated CA (IBR = 13.00) had the most profound impact, followed by CTC (IBR = 12.49) and OTC (IBR = 11.97) had the least influence at the highest concentration (50 mg·kg-1). These results contribute to a deeper understanding of the physiological toxicity of CTC and oxytetracycline alone and in combination on wheat and provide a basis for further assessment of their potential ecological risks.

Integrated multi-omics and DNA stable-isotope probing approaches to reveal soil-ryegrass response to ionic rare earth mineral ammonium-lead contamination

The extensive use of ammonium (NH4+) sulfate in ionic rare earth mining has resulted in soil contamination with NH4+ and lead (Pb), posing significant challenges for ecological restoration. Here, multi-omics and DNA stable-isotope probing (DNA-SIP) approaches were utilized to investigate soil nitrogen cycling and the molecular response of ryegrass (Lolium perenne L.) to NH4+ (180-720 mg kg-1)-Pb2+ (207-828 mg kg-1) co-contamination. A synergistic interaction between NH4+ and Pb2+ was observed, significantly inhibited ryegrass growth, and induced oxidative stress and mitochondrial swelling. The EC50 toxicity thresholds were 383 mg kg⁻¹ for NH4+ and 512 mg kg⁻¹ for Pb. The Integrated Biomarker Response (IBRv2) model elucidated the synergistic toxic effects. Transcriptomic and metabolomic analyses indicated that ryegrass roots enhanced carbon metabolism and antioxidant response pathways related to stress tolerance. Galactose metabolism and lysine degradation were identified as key pathways associated with stress response. Co-contamination with NH4+ and Pb2+ reduced ryegrass root 15N-total nitrogen (TN) by 30 % while increasing soil 15N-NH4+ residue by 95 % and decreasing 15N-microbial biomass nitrogen (MBN) by 59 %, compared to NH4+ single contamination. DNA-SIP analysis revealed that ryegrass cultivation under NH4+- Pb2+ co-contamination increased the abundance of plant growth-promoting rhizobacteria (Dyella), acid-tolerant nitrogen (Acidibacter), and sulfur-cycling taxa (Desulfosporosinus). The presence of raffinose and chlorogenic acid in ryegrass root metabolites was associated with shifts in the structure and composition of using NH4+ active microbial taxa. These findings provide valuable insights into plant-soil-microbe interactions under multi-pollutant stress and offer practical strategies for phytoremediation and ecological restoration in areas affected by mining.

Assessment of the mechanism of combined toxicity of imidacloprid and triadimefon to Secale cereale L. seedlings under freeze-thaw cycle conditions

Freeze-thaw (FT) cycles significantly stress crops in Northeast China, exacerbated by pesticide overuse, particularly affecting vulnerable seedlings during these periods. This study investigates the physiological responses of Secale cereale L. seedlings to the insecticide imidacloprid (IMI) and the fungicide triadimefon (T) under simulated FT conditions. Our findings reveal that both pesticides impair photosynthesis in FT environments, resulting in increased malondialdehyde (MDA) and relative conductivity (RC). Furthermore, exposure to IMI and T enhances the activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX), while decreasing reduced glutathione (GSH) and hydrogen peroxide (H2O2) levels. Notably, combined stress resulted in significant increases of 80.26%, 16.36%, and 87.7% in RC, SOD, and POD activities, respectively, alongside substantial decreases of 65.87%, 46.34%, 63.74%, and 63.78% in net photosynthesis rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and water-use efficiency (WUE) in rye seedlings. Molecular docking analyses indicate that IMI and T interact with the active sites of SOD, POD, and APX through hydrogen bonding, compromising membrane integrity and inducing oxidative stress. While Secale cereale L. seedlings exhibit some resistance to IMI and T, FT conditions reduce this resilience. Correlation analysis reveals significant interactions between FT and pesticide stress on seedling physiology, suggesting that the concurrent use of IMI and T should be minimized in FT-prone areas. This study provides new insights into the pathways and mechanisms underlying the combined toxicity of IMI and T, offering a basis for assessing their environmental impacts on crops in regions susceptible to freeze-thaw cycles.

Growth and physiological responses of spearmint (Mentha spicata) cuttings to norfloxacin

The increasing global consumption of antibiotics is a growing concern for the scientific community since the residues discharged into the environment can accumulate in plants and affect their growth. Mentha spicata L. is commonly used as a spice and widely cultivated as a medicinal and edible crop under controlled environments. Our study aimed to assess the subacute toxicity of norfloxacin (NOR; 0, 5, 10, 20, and 40 mg/L) on M. spicata cuttings and investigate the degradation of NOR in hydroponics during a 14-day exposure under natural conditions. In response to NOR, there were concentration-dependent declines in biomass, chlorophyll a, root activity, root elongation, and obvious chlorosis. An increase in malondialdehyde content and antioxidant activity indicated that NOR exposure specifically led to oxidative stress. There was a slight rise in osmotic regulatory substances observed in the setups treated with NOR compared to the control group. Simultaneously, M. spicata also made a response to the stress of NOR, and phytodegradation plays a more significant role in the degradation of NOR, in addition to hydrolysis and photodegradation processes. The integrated biomarker responses vesion 2 index values gradually increased with rising exposure concentrations, which suggested that NOR had toxic effects on M. spicata. These findings will improve the understanding of fluoroquinolones antibiotic effects on plants.

The ecological security risks of phthalates: A focus on antibiotic resistance gene dissemination in aquatic environments

Antibiotic resistance genes (ARGs) have become a major focus in environmental safety and human health, with concerns about non-antibiotic substances like microplastics facilitating their horizontal gene transfer. Phthalate esters (PAEs), as ubiquitous plastic additives, are prevalent in aquatic environments, yet there remains a dearth of studies examining their impacts on ARG dissemination. This study focuses on dibutyl phthalate (DBP), a prototypical PAE, to assess its potential influence on the conjugative transfer of ARGs along with the related molecular mechanisms. The results revealed that DBP exposure at environmentally relevant concentrations significantly promoted the conjugative transfer of RP4 plasmid-mediated ARGs by up to 2.7-fold compared to that of the control group, whereas it severely suppressed the conjugation at a high concentration (100 μg/L). The promotion of conjugation transfer by low-concentration DBP (0.01-10 μg/L) was mainly attributed to the stimulation of ROS, enhanced membrane permeability, increased energy synthesis, increased polymeric substances secretion, and upregulation of conjugation-related genes. Conversely, high DBP exposure induced oxidative damage and reduced ATP synthesis, resulting in the suppression of ARG conjugation. Notably, donor and recipient bacteria responded differently to DBP-induced oxidative stress. This study explores the environmental behavior of DBP in the water environment from the perspective of ARG propagation and provides essential data and theoretical insights to raise public awareness about the ecological security risks of PAEs.

Nitric oxide application alleviates fungicide and ampicillin co-exposure induced phytotoxicity by regulating antioxidant defense, detoxification system, and secondary metabolism in wheat seedlings

Pesticides and antibiotics usually sink into soil, posing serious phytotoxic effects on plants. However, studies are elusive regarding the phytotoxic effects of fungicide Consento (CON) and antibiotic ampicillin (AMP) co-exposure. Nitric oxide (NO) is an important plant signaling molecule known for abiotic stress tolerance in plants. This study investigated the phytotoxic effects of CON and/or AMP on the growth and antioxidant activities of wheat (Triticum aestivum L.) seedlings and unveiled the underlying mechanisms induced by the application of NO as sodium nitroprusside (SNP; 100 μM) in wheat seedlings exposed to CON and/or AMP in a hydroponic culture. Results revealed that application of CON, AMP, and CON + AMP significantly reduced the shoot length (21, 27, & 42%), root length (49, 41, & 51%), shoot biomass (30, 27, & 35%), root biomass (51, 36, & 56%), Chl-a (24, 19, & 29%), Chl-b (42, 48, & 54%), and carotenoid contents (35, 33, & 35%), respectively, due to significantly higher hydrogen peroxide (231, 151, & 157%) and malondialdehyde production (97, 60, & 148%) in wheat seedlings compared to control plants. However, the application of NO significantly enhanced wheat lengths (38%), biomass (60%), and photosynthetic pigments (67%) on co-exposure to CON + AMP. Moreover, NO treatment significantly lowered hydrogen peroxide (36%) and malondialdehyde contents (35%) in wheat seedlings exposed to CON + AMP stress, indicating the protective role of NO in scavenging reactive oxygen species. Wheat seedlings exposed to the combined stress of CON and AMP regulated antioxidant defense, xenobiotic detoxification, and the phenylpropanoid pathway to combat stress conditions. However, NO application significantly increased CAT (44%), proline (60%), total phenolic (41%), nitrate reductase (53%), and polyphenol oxidase activities (31%) to mitigate CON + AMP stress. These findings suggest NO application as an effective and environmentally friendly approach for detoxification of CON + AMP stress through biosynthesis of secondary metabolic enzymes and regulation of antioxidants for boosting wheat crop resilience under pesticide and antibiotic co-contamination.

Integrated bio-electrochemical approach to Norfloxacin (NFX) degradation: Efficacy, degradation mechanisms, and toxicological insights

Norfloxacin (NFX), a widely used fluoroquinolone antibiotic, poses significant environmental concerns due to its persistence in ecosystems and its potential to foster antibiotic resistance. This study explores the degradation of NFX using a bio-electrochemical system (BES) facilitated by Bacillus subtilis isolated from animal waste sludge. Experimental parameters were optimized to maximize removal efficiency, with the optimal conditions determined as an NFX concentration of 200 mg/L, pH 7, and an applied potential of 1.2 V. The degradation pathway was elucidated through the identification of intermediate products, ultimately leading to the complete mineralization of NFX. To assess the environmental impact of BES-treated water, a series of eco-toxicity assays were conducted. Microbial diversity analysis revealed that soil exposed to BES-treated water maintained a balanced microbial community, contrasting with the disruptions observed in soils exposed to untreated NFX-contaminated water. Phytotoxicity tests, earthworm toxicity assay, and Artemia hatchability & lethality assays further confirmed the reduced toxicity of the BES-treated water. These findings highlight the efficacy of BES in the degradation of NFX, demonstrating its potential as a sustainable strategy for the remediation of antibiotic-contaminated environments and the mitigation of associated ecological risks.

Global hierarchical meta-analysis to identify the factors for controlling effects of antibiotics on soil microbiota

It is widely known that antibiotics can affect the structure and function of soil microbial communities, but the specific degree of impact and controlled factors on different indicators remain inconclusive. We conducted a multiple hierarchical mixed effects meta-analysis on 2564 observations that were extracted from 60 publications, to comprehensively assess the impact of antibiotics on soil microbiota. The results showed that antibiotics had significant negative effects on soil microbial biomass, α-diversity and soil enzyme activity. Under neutral initial soil, when soil was derived from agricultural land or had a fine-textured, the negative impacts of antibiotics on soil microbial community were exacerbated. Both single and mixed additions of antibiotics had significant inhibitory effects on soil microbial enzyme activities. The Random Forest model predicted the following key moderators involved in the effects of antibiotics on the soil microbiome, and antibiotics type, soil texture were key moderators on the severity of soil microbial biomass changes. Soil texture, temperature and single or combined application constitute of antibiotics were the main drivers of effects on soil enzyme activities. The reported results can be helpful to assess the ecological risk of antibiotics in a soil environment and provides a scientific basis for the rational of antibiotics use in the soil environment.

Divergent effects of azithromycin on purple corn (Zea mays L.) cultivation: Impact on biomass and antioxidant compounds

The present study assessed the impact of using irrigation water contaminated with Azithromycin (AZM) residues on the biomass and antioxidant compounds of purple corn; for this purpose, the plants were cultivated under ambient conditions, and the substrate used consisted of soil free from AZM residues, mixed with compost in a ratio of 1:1 (v/v). The experiment was completely randomized with four replications, with treatments of 0, 1, 10, and 100 μg/L of AZM. The results indicate that the presence of AZM in irrigation water at doses of 1 and 10 μg/L increases the weight of dry aboveground biomass, while at an amount of 100 μg/L, it decreases. Likewise, this study reveals that by increasing the concentration of AZM from 1 to 10 μg/L, total polyphenols and monomeric anthocyanins double, in contrast, with an increase to 100 μg/L, these decrease by 44 and 53%, respectively. It has been demonstrated that purple corn exposed to the antibiotic AZM at low doses has a notable antioxidant function in terms of DPPH and ORAC. The content of flavonols, phenolic acids, and flavanols increases by 57, 28, and 83%, respectively, when the AZM concentration is from 1 to 10 μg/L. However, with an increase to 100 μg/L, these compounds decrease by 17, 40, and 42%, respectively. On the other hand, stem length, root length, and dry weight of root biomass are not significantly affected by the presence of AZM in irrigation water.

Interactive effects of ammonium sulfate and lead on alfalfa in rare earth tailings: Physiological responses and toxicity thresholds

Ion-adsorption rare earth ore contains significant levels of leaching agents and heavy metals, leading to substantial co-contamination. This presents significant challenges for ecological rehabilitation, yet there is limited understanding of the toxicity thresholds associated with the co-contamination of ammonium sulfate (AS) and lead (Pb) on pioneer plants. Here, we investigated the toxicity thresholds of various aspects of alfalfa, including growth, ultrastructural changes, metabolism, antioxidant system response, and Pb accumulation. The results indicated that the co-contamination of AS-Pb decreased the dry weight of shoot and root by 26 %-77 % and 18 %-92 %, respectively, leading to irregular root cell morphology and nucleus disintegration. The high concentration and combined exposures to AS and Pb induced oxidative stress on alfalfa, which stimulated the defense of the antioxidative system and resulted in an increase in proline levels and a decrease in soluble sugars. Structural equation modeling analysis and integrated biomarker response elucidated that the soluble sugars, proline, and POD were the key physiological indicators of alfalfa under stresses and indicated that co-exposure induced more severe oxidative stress in alfalfa. The toxicity thresholds under single exposure were 496 (EC5), 566 (EC10), 719 (EC25), 940 (EC50) mg kg-1 for AS and 505 (EC5), 539 (EC10), 605 (EC25), 678 (EC50) mg kg-1 for Pb. This study showed that AS-Pb pollution notably influenced plant growth performance and had negative impacts on the growth processes, metabolite levels, and the antioxidant system in plants. Our findings contribute to a theoretical foundation and research necessity for evaluating ecological risks in mining areas and assessing the suitability of ecological restoration strategies.

Veterinary antibiotics differ in phytotoxicity on oilseed rape grown over a wide range of concentrations

Residues of veterinary antibiotics are a worldwide problem of increasing concern due to their persistence and diverse negative effects on organisms, including crops, and limited understanding of their phytotoxicity. Therefore, this study aimed to compare the phytotoxic effects of veterinary antibiotics tetracycline (TC) and ciprofloxacin (CIP) applied in a wide range of concentrations on model plant oilseed rape (Brassica napus). Overall phytotoxicity of 1-500 mg kg-1 of TC and CIP was investigated based on morphological, biochemical, and physiological plant response. Photosystem II (PSII) performance was suppressed by TC even under environmentally relevant concentration (1 mg kg-1), with an increasing effect proportionally to TC concentration in soil. In contrast, CIP was found to be more phytotoxic than TC when applied at high concentrations, inducing a powerful oxidative burst, impairment of photosynthetic performance, collapse of antioxidative protection and sugar metabolism, and in turn, complete growth retardation at 250 and 500 mg kg-1 CIP treatments. Results of our study suggest that TC and CIP pollution do not pose a significant risk to oilseed rapes in many little anthropogenically affected agro-environments where TC or CIP concentrations do not exceed 1 mg kg-1; however, intensive application of manure with high CIP concentrations (more than 50 mg kg-1) might be detrimental to plants and, in turn, lead to diminished agricultural production and a potential risk to human health.

A group-targeting biosensor for sensitive and rapid detection of quinolones in water samples

BACKGROUND

Quinolones (QNs) widely exist in the environment due to their wide range of applications and poor metabolic properties, resulting in the generation and spread of resistance genes, posing a potential threat to human health. Traditional analytical methods cannot detect all broad ranges of QNs simultaneously. The development of facile, efficient and reliable method for quantification and assessment of the total QNs is a long-lasting challenge.

RESULTS

We hereby provide a simple, sensitive and instantaneous group-targeting biosensor for the detection of total QNs in environmental water samples. The biosensor is based on a group-specific antibodies with high affinity against QNs. Fluorescent labeled antibodies bound to the coated antigen modified on the surface of the transducer, and excited by the evanescent waves. The detected fluorescent signal is inversely proportional to the QNs concentration. This biosensor exhibited excellent performance with detection limits lower than 0.15 μg L-1 for all five QNs variants, and even lower than 0.075 μg L-1 for ciprofloxacin (CIP) and ofloxacin (OFL). Environmental water samples can be detected after simple pretreatment, and all detection steps can be completed in 10 min. The transducer has a high regenerative capacity and shows no significant signal degradation after two hundred detection cycles. The recoveries of QNs in a variety of wastewater range from 105 to 119%, confirming its application potential in the measurement of total QNs in reality.

SIGNIFICANCE

The biosensor can realize rapid and sensitive detection of total QNs in water samples by simple pretreatment, which overcomes the disadvantage of the traditional methods that require complex pretreatment and time-consuming, and pave the groundwork for expansive development centered around this technology.

Ketoprofen exposure perturbs nitrogen assimilation and ATP synthesis in rice roots: An integrated metabolome and microbiome analysis

Ketoprofen, a commonly used non-steroidal anti-inflammatory drug (NSAID), can enter farmland environments via sewage irrigation and manure application and is toxic to plants. However, there have been relatively few studies on the association of ketoprofen with nitrogen (N) assimilation and metabolic responses in plants. Accordingly, the goal of this study was to investigate the effects of ketoprofen on ATP synthesis and N assimilation in rice roots. The results showed that with increasing ketoprofen concentration, root vitality, respiration rate, ATP content, and H+-ATPase activity decreased and plasma membrane permeability increased. The expressions of OSA9, a family III H+-ATPase gene, and OSA6 and OSA10, family IV genes, were upregulated, indicating a response of the roots to ketoprofen. Nitrate, ammonium, and free amino acids content decreased with increased ketoprofen. The levels of enzymes involved in N metabolism, namely nitrate reductase, nitrite reductase, glutamine synthetase, glutamate synthetase, and glutamate dehydrogenase, also decreased under ketoprofen treatment. Principal component analysis revealed that ketoprofen treatment can significantly affect energy synthesis and nitrogen assimilation in rice roots, while these effects can be alleviated by the antioxidant response. Most of the metabolite contents increased, including amino acids, carbohydrates, and secondary metabolites. Key metabolic pathways, namely substance synthesis and energy metabolism, were found to be disrupted. Microbiome analysis showed that community diversity and richness of rice root microorganisms in solution increased with increasing levels of ketoprofen treatment, and the microbial community structure and metabolic pathways significantly changed. The results of this study provides new insights into the response of rice roots to ketoprofen.

Comparative study of the toxicity mechanisms of quinolone antibiotics on soybean seedlings: Insights from molecular docking and transcriptomic analysis

The ecological effects of quinolone antibiotics (QNs) on non-target organisms have received widespread attention. The toxicological mechanisms of three common QNs, that is, enrofloxacin, levofloxacin, and ciprofloxacin, on soybean seedlings were investigated in this study. Enrofloxacin and levofloxacin caused significant growth inhibition, ultrastructural alterations, photosynthetic suppression, and stimulation of the antioxidant system, with levofloxacin exhibiting the strongest toxic effects. Ciprofloxacin (<1 mg·L-1) did not have a significant effect on the soybean seedlings. As the concentrations of enrofloxacin and levofloxacin increased, antioxidant enzyme activities, malondialdehyde content, and hydrogen peroxide levels also increased. Meanwhile, the chlorophyll content and chlorophyll fluorescence parameters decreased, indicating that the plants underwent oxidative stress and photosynthesis was suppressed. The cellular ultrastructure was also disrupted, which was manifested by swollen chloroplasts, increased starch granules, disintegration of plastoglobules, and mitochondrial degradation. The molecular docking results suggested that the QNs have an affinity for soybean target protein receptors (4TOP, 2IUJ, and 1FHF), with levofloxacin having the highest binding energy (-4.97, -3.08, -3.8, respectively). Transcriptomic analysis has shown that genes were upregulated under the enrofloxacin and levofloxacin treatments were mainly involved in ribosome metabolism and processes to synthesize oxidative stress-related proteins. Downregulated genes in the levofloxacin treatment were primarily enriched in photosynthesis-related pathways, indicating that levofloxacin significantly inhibited gene expression for photosynthesis. Genes expression level by quantitative real-time PCR analysis was consistent with the transcriptomic results. This study confirmed the toxic effect of QNs on soybean seedlings, and provided new insights into the environmental risks of antibiotics.

Antibiotics induced changes in nitrogen metabolism and antioxidative enzymes in mung bean (Vigna radiata)

Excessive use and release of antibiotics into the soil environment in the developing world have resulted in altered soil processes affecting terrestrial organisms and posing a serious threat to crop growth and productivity. The present study investigated the influence of exogenously applied oxytetracycline (OXY) and levofloxacin (LEV) on plant physiological responses, key enzymes involved in nitrogen metabolism (e.g., nitrate reductase, glutamine synthetase), nitrogen contents and oxidative stress response of mung bean (Vigna radiata). Plants were irrigated weekly with antibiotics containing water for exposing the plants to different concentrations i.e., 1, 10, 20, 50, and 100 mg L-1. Results showed a significant decrease in nitrate reductase activity in both antibiotic treatments and their mixtures and increased antioxidant enzymatic activities in plants. At lower concentrations of antibiotics (≤20 mg L-1), 53.9 % to 78.4 % increase in nitrogen content was observed in levofloxacin and mixtures compared to the control, resulting in an increase in the overall plant biomass. Higher antibiotic (≥50 mg L-1) concentration showed 58 % decrease in plant biomass content and an overall decrease in plant nitrogen content upon exposure to the mixtures. This was further complemented by 22 % to 42 % increase in glutamine synthetase activity observed in the plants treated with levofloxacin and mixtures. The application of low doses of antibiotics throughout the experiments resulted in lower toxicity symptoms in the plants. However, significantly higher malondialdehyde (MDA) concentrations at higher doses (20 mg L-1 and above) than the control showed that plants' tolerance against oxidative stress was conceded with increasing antibiotic concentrations. The toxicity trend was: levofloxacin > mixture > oxytetracycline.