Biotransformation of tetracycline by a novel bacterial strain Stenotrophomonas maltophilia DT1

Subtleties of tetracycline removal during growth of microalgae-fungi consortia: Mechanistic insights from perspectives of extra- and intracellular metabolites

This study focused on tetracycline (TC) as the target antibiotic and utilized the emerging microbial system microalgae-fungi consortia to treat it. Results indicate that consortia composed of microalgae Chlorella sp. HL and fungi HW12 (Aspergillus caespitosus) (HL-HW12) exhibited the optimum TC removal (93.00 %, residual concentration: 2.73 mg/L) and biomass harvesting efficiency (92.69 %) among the five kinds of constructed microalgae-fungi consortia. Mechanism analysis indicated that outside the cell, microalgae-fungi consortia strengthened TC removal and biomass harvesting by augmenting the contents of proteins, polysaccharides, fulvic acids, and humic acids. While within the cell, microalgae-fungi consortia adjusted the abundance of critical metabolites in the amino acid metabolism, nucleotide metabolism, and other metabolic pathways to cope with the coercion of TC and facilitated its elimination. This study not only provides good TC microbial treatment systems but also comprehensively reveals the TC removal and metabolic response mechanisms by microalgae-fungi consortia.

Cooperation of Lactoplantibacillus plantarum and polyethylene microplastics facilitated the disappearance of tetracycline during anaerobic fermentation of whole plant maize

In agricultural production systems, the harm of both antibiotics and microplastics (MPs) to human health has been an important and continuously concerned issue. A small bagged silage production system was designed to investigate the effects of Lactoplantibacillus plantarum, polyethylene (PE) -MPs and their mixture on the silage fermentation and chemical composition of Tetracycline (TET) -contaminated whole plant maize. In addition, the bacterial community of silage samples was analyzed by using next generation genome sequencing technology. The formation of an extremely acidic environment (pH < 3.8) by ensiling effectively promoted the degradation of tetracycline (about 12.36 ng/ml), with PE-MPs particles also cleaved from 100 μm to 10 μm (in diameter) after 60 days of anaerobic storage. The PE-MPs physically adsorbed TET through its special pore structure and interacted with silage fermentation-dominated microorganisms including Lacticaseibacillus with relative abundances of 33-95 %, where the combination of PE-MPs and L. plantarum degrades tetracycline to 7.05 ng/ml. The PE-MPs inclusion enhanced the fermentation function of Lacticaseibacillus and stabilized the pH, ammonia nitrogen and other chemical indices of silage mass. Importantly, the co-occurrence of PE-MPs sustained also the dominance of desirable Lacticaseibacillus at late stage of ensiling with TET-contaminated maize. Therefore, the combination of PE-MPs and L. plantarum counteracted undesirable silage fermentation from TET contamination, reduced hypothetically the risks to animal and even human health by unappreciated use of antibiotics in agricultural production system.

Response surface methodology and Box-Behnken design optimization of Sulfaquinoxaline removal efficiency and degradation mechanisms by Bacillus sp. strain DLY-11

Antibiotic pollution, particularly the persistence of Sulfaquinoxaline (SQ) residues in livestock and poultry farming environments, has emerged as a pressing environmental concern. Despite this, there remains a limited understanding of the optimized conditions and mechanisms for the efficient degradation of SQ by microorganisms. To address this knowledge gap, we isolated Bacillus sp. strain DLY-11 from aerobically composted manure, which exhibits exceptional SQ degradation capability. Using response surface methodology and Box-Behnken design, we optimized the conditions: 5 % inoculum, 60 °C, pH 8.02, and 0.5 g/L MgSO4. Strain DLY-11 achieved 95.5 % SQ degradation in 2 d. We identified 12 degradation products, including one newly reported, and proposed four degradation pathways involving S-N and C-N bond cleavage, hydroxylation, SO2 release, deamination, oxidation, acetylation, and formylation. One of the proposed pathways is entirely new and has not been previously reported in the literature. This work closes important information gaps in the bacterial degradation pathways of SQ by optimizing the degradation conditions and introducing a useful microbial resource for the effective breakdown of SQ. It also provides a solid theoretical foundation for tackling the problem of antibiotic contamination in livestock and poultry production.

Potential of newly isolated strain Pseudomonas aeruginosa MC-1/23 for the bioremediation of soil contaminated with selected non-steroidal anti-inflammatory drugs

The widespread usage of non-steroidal anti-inflammatory drugs (NSAIDs) has resulted in their significant accumulation in the environment, necessitating the development of effective methods for their removal. This study primarily isolated a bacterial strain capable of degrading specific NSAIDs and evaluated its potential for eliminating these drugs from contaminated soil through bioaugmentation. The objectives were achieved by assessing the degradation rates of ibuprofen (IBF), diclofenac (DCF), and naproxen (NPX) in liquid media and soil samples inoculated with a newly identified strain, Pseudomonas aeruginosa MC-1/23. In addition, the effect of natural soil microflora and abiotic conditions on the breakdown of the tested NSAIDs was examined. The findings revealed that strain MC-1/23 could metabolize these compounds in a mineral salt medium, utilizing them as carbon and energy sources, suggesting metabolic degradation. When nonsterile soil was augmented with the P. aeruginosa MC-1/23 strain, the degradation rates of the drugs significantly improved, as evidenced by reductions in t1/2 values by 5.3-, 1.4-, and 5.8-fold for IBF, DCF, and NPX, respectively, compared with soil containing only natural microflora. These results confirm that the introduced strain enhances the catabolic potential of existing microflora. Thus, the strain’s degradation and bioremediation capabilities offer valuable applications for remediating NSAID-contaminated soils.

Biodegradation of tetracycline by Cladosporium colombiae T1: performance and degradative pathway

The microbial degradation of tetracycline (TC) represents an effective bioremediation method. An effective TC-degrading strain of Cladosporium colombiae T1 was isolated from chicken manure using enrichment techniques. Response surface methodology was employed to ascertain the optimal conditions for removing TC by strain T1, identified as a temperature of 40.00 °C, solution pH of 6.92, TC concentration of 42.99 mg/L, and inoculum dose of 1.98%. The inhibitory effect of TC degradation products on Escherichia coli was investigated using the paper diffusion method. The results demonstrated that the toxicity of TC degradation products by T1 was lower than that of the parent compound. The shake-flask batch experiments showed that the biodegradation of TC was a synergistic effect of intra- and extracellular enzymes, with intracellular enzymes exhibiting greater efficacy in TC degradation (48.56%). LC-MS analysis identified ten potential biodegradation products, and biodegradation pathways were proposed. This study offers a theoretical foundation for the characterization and mechanistic investigation of TC degradation in the environment by Cladosporium colombiae T1.

Veterinary tetracycline residues: Environmental occurrence, ecotoxicity, and degradation mechanism

Tetracycline has been widely used in the intensive livestock and poultry breeding industry to prevent and treat infectious diseases or promote animal growth. Usually, about 40.0-90.0% of tetracycline is excreted in the form of original drugs or metabolites and finally enters the surrounding water and soil, causing a series of eco-toxic effects. In this review, the toxic effects on plants, soil animals, and microorganisms are systematically reviewed. The migration and degradation mechanisms of tetracycline are emphasized, which are closely related to the physical and chemical properties of soil. In addition, the residual tetracycline in soil and water can be efficiently degraded by "plant-microorganism". Based on summarizing the current research progress, this review puts forward some important problems to be solved in the study of tetracycline residue and looks forward to the future research direction.

Enhanced Dissipation of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) in Soil by the Bioaugmentation with Newly Isolated Strain Acinetobacter johnsonii MC5

The presented study investigated the possibility of using the Acinetobacter johnsonii MC5 strain, isolated from raw sewage by the enrichment culture method, in the bioremediation of soil contaminated with selected NSAIDs, i.e., ibuprofen (IBF), diclofenac (DCF), and naproxen (NPX), using the bioaugmentation technique. The degradation potential of A. johnsonii MC5 was first evaluated using a mineral salt medium containing drugs as the only sources of carbon and energy. The results show that the strain MC5 was capable of utilizing the tested compounds in medium, indicating that the drugs might be metabolically degraded. IBF and NPX were degraded with a similar rate and DT50 values were determined to be approximately 5 days, while the degradation process for DCF was slower, and the DT50 value was about 5 times higher (22.7 days) compared to those calculated for IBF and NPX. Bioaugmentation of non-sterile soil with A. johnsonii MC5 increased the rate of disappearance of the tested drugs, and DT50 values decreased 5.4-, 3.6-, or 6.5-fold for IBF, DCF, or NPX, respectively, in comparison with the values obtained for the soil with indigenous microorganisms only. The obtained results suggest that A. johnsonii MC5 may have potential for use in bioremediation of NSAID-contaminated soils; however, detailed studies are needed before using this strain in such process on a larger scale.

Occurrence, fate and control strategies of heavy metals and antibiotics in livestock manure compost land application: A review

Composting is a sustainable method for managing livestock manure, but the residual heavy metals and antibiotics in the compost pose can pose environmental risks when applied to land. Although many studies focus on occurrence and risk mitigation of heavy metals and antibiotics in manure compost land application, there is a lack of systematic analysis covering the entire chain from source to process and final disposal. Given this, this article provides a comprehensive review of the sources, migration, fate, risk assessment, and risk reduction of heavy metals and antibiotics contamination in land application of livestock manure compost for the first time. The main pollutants of concern are heavy metals, particularly Cu and Zn, and antibiotics such as quinolones, tetracyclines, and sulfonamides. The coexistence of these contaminants can easily trigger co-contamination, threatening soil ecosystems and human health. Risk reduction strategies, emphasizing the use of additives during composting and phytoremediation after land application, are discussed. Challenges remain in understanding the interactions between heavy metals and antibiotics and developing effective strategies for mitigating co-contamination. Furthermore, the paper proposes the future prospects on the interactions study and the simultaneous control strategy of heavy metals and antibiotics contamination. It is expected to promote the whole process management of livestock manure and the control of heavy metal-antibiotic co-contamination in the future.

Tetracycline removal by immobilized indigenous bacterial consortium using biochar and biomass: Removal performance and mechanisms

The significant influx of antibiotics into the environment represents ecological risks and threatens human health. Microbial degradation stands as a highly effective method for reducing antibiotic pollution. This study explored the potential of immobilized microbial consortia to efficiently degrade tetracycline. Concurrently, the suitability of different immobilization materials were assessed, with reed charcoal-immobilized consortia exhibiting the highest efficiency in removing tetracycline (92%). Similarly, wheat-bran-loaded bacterial consortia displayed a remarkable 11.43-fold increase in tetracycline removal compared with free consortia. Moreover, adding the carriers increased the nutrients, while the activities of both intracellular and extracellular catalases increased significantly post-immobilization, thus highlighting this enzyme's crucial role in tetracycline degradation. Finally, analysis of the microbial communities revealed the prevalence of Achromobacter and Parapedobacter, signifying their potential as key degraders. Overall, the immobilized consortia not only hold promise for application in the bioremediation of tetracycline-contaminated environment but also provide theoretical underpinnings for environmental remediation by microorganisms.

Co-metabolism of microorganisms: A study revealing the mechanism of antibiotic removal, progress of biodegradation transformation pathways

The widespread use of antibiotics has resulted in large quantities of antibiotic residues entering aquatic environments, which can lead to the development of antibiotic-resistant bacteria and antibiotic-resistant genes, posing a potential environmental risk and jeopardizing human health. Constructing a microbial co-metabolism system has become an effective measure to improve the removal efficiency of antibiotics by microorganisms. This paper reviews the four main mechanisms involved in microbial removal of antibiotics: bioaccumulation, biosorption, biodegradation and co-metabolism. The promotion of extracellular polymeric substances for biosorption and extracellular degradation and the regulation mechanism of enzymes in biodegradation by microorganisms processes are detailed therein. Transformation pathways for microbial removal of antibiotics are discussed. Bacteria, microalgae, and microbial consortia's roles in antibiotic removal are outlined. The factors influencing the removal of antibiotics by microbial co-metabolism are also discussed. Overall, this review summarizes the current understanding of microbial co-metabolism for antibiotic removal and outlines future research directions.

Study on the biodegradation characteristics and mechanism of tetracycline by Serratia entomophila TC-1

Microbial degradation is an important solution for antibiotic pollution in livestock and poultry farming wastes. This study reports the isolation and identification of the novel bacterial strain Serratia entomophila TC-1, which can degrade 87.8 % of 200 mg/L tetracycline (TC) at 35 °C, pH 6.0, and an inoculation amount of 1 % (v/v). Based on the intermediate products, a possible biological transformation pathway was proposed, including dehydration, oxidation ring opening, decarbonylation, and deamination. Using Escherichia coli and Bacillus subtilis as biological indicators, TC degraded metabolites have shown low toxicity. Whole-genome sequencing showed that the TC-1 strain contained tet (d) and tet (34), which resist TC through multiple mechanisms. In addition, upon TC exposure, TC-1 participated in catalytic and energy supply activities by regulating gene expression, thereby playing a role in TC detoxification. We found that TC-1 showed less interference with changes in the bacterial community in swine wastewater. Thus, TC-1 provided new insights into the mechanisms responsible for TC biodegradation and can be used for TC pollution treatment.

Green Synthesis of Boric Acid Modified Bismuth Based Non-Toxic Perovskite Quantum Dots for Highly Sensitive Detection of Oxytetracycline

In recent years, perovskite quantum dots (PQDs) have successfully attracted widespread attention due to their excellent optical properties. However, the instability and toxicity problems of perovskite quantum dots are the main obstacles limiting their applications. In this work, bismuth-based perovskite quantum dots were synthesized by a ligand-assisted reprecipitation method, based on which a novel boric acid-functionalized bismuth-based non-toxic perovskite quantum dots fluorescent sensor (Cs3Bi2Br9-APBA) that can be stabilized in the ethanol phase was prepared by a boron affinity technique. Based on the covalent binding interaction of Cs3Bi2Br9-APBA with oxytetracycline (OTC), a highly selective and sensitive method for the detection of OTC was developed, which effectively solved the problems of poor stability and toxicity in the application of perovskite quantum dots. Under the optimal conditions, the fluorescence intensity of the synthesized Cs3Bi2Br9-APBA was linear with the concentration range of 0.1 ∼ 18 µM OTC, and the detection limit could reach 0.0802 µM. The fluorescence detection mechanism was explored and analyzed by spectral overlap analysis, suppression efficiency study of observed and corrected fluorescence, and fluorescence lifetime decay curve fitting, the mechanism of OTC detection by Cs3Bi2Br9-APBA was identified as the inner filter effect (IFE). In addition, the sensor successfully realized the quantitative detection of trace OTC in the environment, and our study provides a new idea for the preparation of green perovskite materials with high stability and selectivity.

Effects and mechanisms of aquatic landscape plants on the removal of veterinary antibiotics from hydroponic solutions

Four aquatic landscape plants and three veterinary antibiotics were selected to construct a hydroponic test system to analyze the tolerance, removal effect and mechanism of antibiotics. The results indicated that antibiotic concentrations from 0 to 100 μg·L-1 promoted plant heights and leaf chlorophyll contents, while antibiotics at concentrations > 100 μg·L-1 had inhibitory effects. The ability of different plants to remove antibiotics was Acorus calamus L. > Ceratophyllum demersum L. > Thalia dealbata Fraser > Nuphar pumila (Timm) DC. The plants with the best removal of norfloxacin, sulfadimethoxine and chlortetracycline were Ceratophyllum demersum L., Acorus calamus L. and Acorus calamus L. after 12 d of hydroponic cultivation using 100 μg·L-1 antibiotics, with removal rates of 66.6%, 63.0% and 63.2%, respectively. The accumulation of antibiotics in different plant tissues was root > stem > leaf and the accumulation increased with incubation time. The diversity of plant root biofilm microorganisms decreased with increasing treatment concentrations of antibiotics, while the abundance of dominant genera (Aeromonas, Bacillus, Lysinibacillus, Providencia, and Staphylococcus) showed an increasing trend. The findings imply that the antibiotic uptake by plants and the dynamics of the rhizosphere microbial community combine to promote antibiotic removal.

Biodegradation and bioaugmentation of tetracycline by Providencia stuartii TX2: Performance, degradation pathway, genetic background, key enzymes, and application risk assessment

The antibiotic tetracycline (TC) is an emerging pollutant frequently detected in various environments. Biodegradation is a crucial approach for eliminating TC contamination. However, only a few efficient TC-degrading bacteria have been isolated, and the molecular mechanisms of TC degradation, as well as their application potential, remain poorly understood. This study isolated a novel TC-degrading bacterium, Providencia stuartii TX2, from the intestine of black soldier fly larvae. TX2 exhibited remarkable performance, degrading 72.17 % of 400 mg/L TC within 48 h. Genomic analysis of TX2 unveiled the presence of antibiotic resistance genes and TC degradation enzymes. Transcriptomic analysis highlighted the roles of proteins related to efflux pumps, enzymatic transformation, adversity resistance, and unknown functions. Three TC degradation pathways were proposed, with TC being transformed into 27 metabolites through epimerization, hydroxylation, oxygenation, ring opening, and de-grouping, reducing TC toxicity. Additionally, TX2 significantly enhanced TC biodegradation in four TC-contaminated environmental samples and reduced antibiotic resistance genes and mobile genetic elements in chicken manure. This research provides insights into the survival and biodegradation mechanisms of Providencia stuartii TX2 and evaluates its potential for environmental bioremediation.

Reducing residual chlortetracycline in wastewater using a whole-cell biocatalyst

Antibiotic contamination has become an increasingly important environmental problem as a potentially hazardous emergent and recalcitrant pollutant that poses threats to human health. In this study, manganese peroxidase displayed on the outer membrane of Escherichia coli as a whole-cell biocatalyst (E. coli MnP) was expected to degrade antibiotics. The manganese peroxidase activity of the whole-cell biocatalyst was 13.88 ± 0.25 U/L. The typical tetracycline antibiotic chlortetracycline was used to analyze the degradation process. Chlortetracycline at 50 mg/L was effectively transformed via the whole-cell biocatalyst within 18 h. After six repeated batch reactions, the whole-cell biocatalyst retained 87.2 % of the initial activity and retained over 87.46 % of the initial enzyme activity after storage at 25°C for 40 days. Chlortetracycline could be effectively removed from pharmaceutical and livestock wastewater by the whole-cell biocatalyst. Thus, efficient whole-cell biocatalysts are effective alternatives for degrading recalcitrant antibiotics and have potential applications in treating environmental antibiotic contamination.

Fabrication and optimization of bioelectrochemical system using tetracycline-degrading bacterial strains for antibiotic wastewater treatment

In this study, a microbial fuel cell was constructed using Raoultella sp. XY-1 to efficiently degrade tetracycline (TC) and assess the effectiveness of the electrochemical system. The degradation rate reached 83.2 ± 1.8 % during the 7-day period, in which the system contained 30 mg/L TC, and the degradation pathway and intermediates were identified. Low concentrations of TC enhanced anodic biofilm power production, while high concentrations of TC decreased the electrochemical activity of the biofilm, extracellular polymeric substances, and enzymatic activities associated with electron transfer. Introducing electrogenic bacteria improved power generation efficiency. A three-strain hybrid system was fabricated using Castellaniella sp. A3, Castellaniella sp. A5 and Raoultella sp. XY-1, leading to the enhanced TC degradation rate of 90.4 % and the increased maximum output voltage from 200 to 265 mV. This study presents a strategy utilizing tetracycline-degrading bacteria as bioanodes for TC removal, while incorporating electrogenic bacteria to enhance electricity generation.

Unraveling the effects and mechanisms of antibiotics on aerobic simultaneous nitrogen and phosphorus removal by Acinetobacter indicus CZH-5

The effects of antibiotics, such as tetracycline, sulfamethoxazole, and ciprofloxacin, on functional microorganisms are of significant concern in wastewater treatment. This study observed that Acinetobacter indicus CZH-5 has a limited capacity to remove nitrogen and phosphorus using antibiotics (5 mg/L) as the sole carbon source. When sodium acetate was supplied (carbon/nitrogen ratio = 7), the average removal efficiencies of ammonia-N, total nitrogen, and orthophosphate-P increased to 52.46 %, 51.95 %, and 92.43 %, respectively. The average removal efficiencies of antibiotics were 84.85 % for tetracycline, 39.32 % for sulfamethoxazole, 18.85 % for ciprofloxacin, and 23.24 % for their mixtures. Increasing the carbon/nitrogen ratio to 20 further improved the average removal efficiencies to 72.61 % for total nitrogen and 97.62 % for orthophosphate-P (5 mg/L antibiotics). Additionally, the growth rate and pollutant removal by CZH-5 were unaffected by the presence of 0.1-1 mg/L antibiotics. Transcriptomic analysis revealed that the promoted translation of aceE, aarA, and gltA genes provided ATP and proton -motive forces. The nitrogen metabolism and polyphosphate genes were also affected. The expression of acetate kinase, dehydrogenase, flavin mononucleotide enzymes, and cytochrome P450 contributed to antibiotic degradation. Intermediate metabolites were investigated to determine the reaction pathways.

Glutamicibacter nicotianae AT6: A new strain for the efficient biodegradation of tilmicosin

The degradation of tilmicosin (TLM), a semi-synthetic 16-membered macrolide antibiotic, has been receiving increasing attention. Conventionally, there are three tilmicosin degradation methods, and among them microbial degradation is considered the best due to its high efficiency, eco-friendliness, and low cost. Coincidently, we found a new strain, Glutamicibacter nicotianae sp. AT6, capable of degrading high-concentration TLM at 100 mg/L with a 97% removal efficiency. The role of tryptone was as well investigated, and the results revealed that the loading of tryptone had a significant influence on TLM removals. The toxicity assessment indicated that strain AT6 could efficiently convert TLM into less-toxic substances. Based on the identified intermediates, the degradation of TLM by AT6 processing through two distinct pathways was then proposed.

Impact of veterinary pharmaceuticals on environment and their mitigation through microbial bioremediation

Veterinary medications are constantly being used for the diagnosis, treatment, and prevention of diseases in livestock. However, untreated veterinary drug active compounds are interminably discharged into numerous water bodies and terrestrial ecosystems, during production procedures, improper disposal of empty containers, unused medication or animal feed, and treatment procedures. This exhaustive review describes the different pathways through which veterinary medications enter the environment, discussing the role of agricultural practices and improper disposal methods. The detrimental effects of veterinary drug compounds on aquatic and terrestrial ecosystems are elaborated with examples of specific veterinary drugs and their known impacts. This review also aims to detail the mechanisms by which microbes degrade veterinary drug compounds as well as highlighting successful case studies and recent advancements in microbe-based bioremediation. It also elaborates on microbial electrochemical technologies as an eco-friendly solution for removing pharmaceutical pollutants from wastewater. Lastly, we have summarized potential innovations and challenges in implementing bioremediation on a large scale under the section prospects and advancements in this field.

Enhanced removal of antibiotics and heavy metals in aquatic systems using spent mushroom substrate-derived biochar integrated with Herbaspirillum huttiense

A novel integrated removal strategy was developed to enhance the concurrent elimination of copper (Cu), zinc (Zn), oxytetracycline (OTC), and enrofloxacin (ENR) from the aqueous environments. The underlying adsorption mechanisms of spent mushroom substrate (SMSB) and the Herbaspirillum huttiense strain (HHS1), and their efficacy in removing Cu, Zn, OTC, and ENR was also examined. Results showed that the SMSB-HHS1 composite stabilized 29.86% of Cu and 49.75% of Zn and achieved removal rates of 97.95% for OTC and 59.35% for ENR through a combination of chemisorption and biodegradation. Zinc did not affect Cu adsorption, and ENR did not impact the adsorption of OTC on SMSB. However, the co-presence of OTC and ENR modified the adsorption behaviors of both Cu and Zn. Copper and Zn enhanced the adsorption of OTC and ENR by serving as bridging agents, facilitating the interaction between the contaminants and SMSB. Conversely, OTC and ENR inhibited the adsorption process of Cu by obstructing its interaction with the SMSB and occupying the oxygen-containing functional groups. The ‒OH (3415 cm-1) and C-O-C (1059 cm-1) functional groups were identified as the principal active sites to form hydrogen bonds and interact with Cu and Zn, leading to the formation of CuP4O11 and Zn4CO3(OH)6H2O. HHS1 also enhanced antibiotic removal through biodegradation, as evidenced by the decrease of ‒C‒O and increase of ‒C = O groups. This study underscores the innovative potential of the SMSB-HHS1 composite, offering a sustainable approach to addressing multifaceted pollution challenges in the aquatic environments.

Biodegradation of atrazine and nicosulfuron by Streptomyces nigra LM01: Performance, degradative pathway, and possible genes involved

Microbial herbicide degradation is an efficient bioremediation method. In this study, a strain of Streptomyces nigra, LM01, which efficiently degrades atrazine and nicosulfuron, was isolated from a corn field using a direct isolation method. The degradation effects of the identified strain on two herbicides were investigated and optimized using an artificial neural network. The maximum degradation rates of S. nigra LM01 were 58.09 % and 42.97 % for atrazine and nicosulfuron, respectively. The degradation rate of atrazine in the soil reached 67.94 % when the concentration was 108 CFU/g after 5 d and was less effective than that of nicosulfuron. Whole genome sequencing of strain LM01 helped elucidate the possible degradation pathways of atrazine and nicosulfuron. The protein sequences of strain LM01 were aligned with the sequences of the degraded proteins of the two herbicides by using the National Center for Biotechnology Information platform. The sequence (GE005358, GE001556, GE004212, GE005218, GE004846, GE002487) with the highest query cover was retained and docked with the small-molecule ligands of the herbicides. The results revealed a binding energy of - 6.23 kcal/mol between GE005358 and the atrazine ligand and - 6.66 kcal/mol between GE002487 and the nicosulfuron ligand.

Microbial Degradation of Tetracycline Antibiotics: Mechanisms and Environmental Implications

The escalating global consumption of tetracyclines (TCs) as broad-spectrum antibiotics necessitates innovative approaches to mitigate their pervasive environmental persistence and associated risks. While initiatives such as China's antimicrobial reduction efforts highlight the urgency of responsible TC usage, the need for efficient degradation methods remains paramount. Microbial degradation emerges as a promising solution, offering novel insights into degradation pathways and mechanisms. Despite challenges, including the optimization of microbial activity conditions and the risk of antibiotic resistance development, microbial degradation showcases significant innovation in its cost-effectiveness, environmental friendliness, and simplicity of implementation compared to traditional degradation methods. While the published reviews have summarized some aspects of biodegradation of TCs, a systematic and comprehensive summary of all the TC biodegradation pathways, reactions, intermediates, and final products including ring-opening products involved with enzymes and mechanisms of each bacterium and fungus reported is necessary. This review aims to fill the current gap in the literature by offering a thorough and systematic overview of the structure, bioactivity mechanism, detection methods, microbial degradation pathways, and molecular mechanisms of all tetracycline antibiotics in various microorganisms. It comprehensively collects and analyzes data on the microbial degradation pathways, including bacteria and fungi, intermediate and final products, ring-opening products, product toxicity, and the degradation mechanisms for all tetracyclines. Additionally, it points out future directions for the discovery of degradation-related genes/enzymes and microbial resources that can effectively degrade tetracyclines. This review is expected to contribute to advancing knowledge in this field and promoting the development of sustainable remediation strategies for contaminated environments.

Development and assessment of an immobilized bacterial alliance that efficiently degrades tylosin in wastewater

Microbial degradation of tylosin (TYL) is a safe and environmentally friendly technology for remediating environmental pollution. Kurthia gibsonii (TYL-A1) and Klebsiella pneumonia (TYL-B2) were isolated from wastewater; degradation efficiency of the two strains combined was significantly greater than either alone and resulted in degradation products that were less toxic than TYL. With Polyvinyl alcohol (PVA)-sodium alginate (SA)-activated carbon (AC) used to form a bacterial immobilization carrier, the immobilized bacterial alliance reached 95.9% degradation efficiency in 1 d and could be reused for four cycles, with > 93% degradation efficiency per cycle. In a wastewater application, the immobilized bacterial alliance degraded 67.0% TYL in 9 d. There were significant advantages for the immobilized bacterial alliance at pH 5 or 9, with 20 or 40 g/L NaCl, or with 10 or 50 mg/L doxycycline. In summary, in this study, a bacterial consortium with TYL degradation ability was constructed using PVA-SA-AC as an immobilized carrier, and the application effect was evaluated on farm wastewater with a view to providing application guidance in environmental remediation.

Environmental consequences of transformation products from an antibiotic mixture and their mitigation in a wastewater microbiome using an HCl-modified adsorbent

This study enhanced our understanding of antibiotic mixtures' occurrence, transformation, toxicity, and ecological risks. The role of acid-modified biochar (BC) in treating antibiotic residues was explored, shedding light on how BC influences the fate, mobility, and environmental impact of antibiotics and transformation products (TPs) in an activated sludge (AS) microbiome. A mixture of oxytetracycline and sulfamethoxazole was found to synergistically (or additively) inhibit cell growth of AS and disrupt the microbiome structure, species richness/diversity, and function. The formation of TPs with potentially higher toxicity and persistence than the original compounds was identified, explaining the microbiome disruption. Agricultural waste-derived BC was optimized for contaminant adsorption, leading to a reduction in toxicity when added to AS by sequestering TPs on its surface. This work highlighted adsorbents as a practical engineering strategy for mitigating liquid-phase contaminants' toxicological consequences, proactively controlling the fate and effects of antibiotics and TPs.

Promising bioprocesses for the efficient removal of antibiotics and antibiotic-resistance genes from urban and hospital wastewaters: Potentialities of aerobic granular systems

The use, overuse, and improper use of antibiotics have resulted in higher levels of antibiotic-resistant bacteria (ARB) and antibiotic-resistance genes (ARGs), which have profoundly disturbed the equilibrium of the environment. Furthermore, once antibiotic agents are excreted in urine and feces, these substances often can reach wastewater treatment plants (WWTPs), in which improper treatments have been highlighted as the main reason for stronger dissemination of antibiotics, ARB, and ARGs to the receiving bodies. Hence, achieving better antibiotic removal capacities in WWTPs is proposed as an adequate approach to limit the spread of antibiotics, ARB, and ARGs into the environment. In this review, we highlight hospital wastewater (WW) as a critical hotspot for the dissemination of antibiotic resistance due to its high level of antibiotics and pathogens. Hence, monitoring the composition and structure of the bacterial communities related to hospital WW is a key factor in controlling the spread of ARGs. In addition, we discuss the advantages and drawbacks of the current biological WW treatments regarding the antibiotic-resistance phenomenon. Widely used conventional activated sludge technology has proved to be ineffective in mitigating the dissemination of ARB and ARGs to the environment. However, aerobic granular sludge (AGS) technology is a promising technology-with broad adaptability and excellent performance-that could successfully reduce antibiotics, ARB, and ARGs in the generated effluents. We also outline the main operational parameters involved in mitigating antibiotics, ARB, and ARGs in WWTPs. In this regard, WW operation under long hydraulic and solid retention times allows better removal of antibiotics, ARB, and ARGs independently of the WW technology employed. Finally, we address the current knowledge of the adsorption and degradation of antibiotics and their importance in removing ARB and ARGs. Notably, AGS can enhance the removal of antibiotics, ARB, and ARGs due to the complex microbial metabolism within the granular biomass.

Simultaneous adsorption and biodegradation of oxytetracycline in wastewater by Mycolicibacterium sp. immobilized on magnetic biochar

Due to the adverse effects of long-term oxytetracycline (OTC) residues in aquatic environments, an effective treatment is urgently needed. Immobilized microbial technology has been widely explored in the treatment of various organic pollutants in aquatic environments with its excellent environmental adaptability. Nevertheless, studies on its application in the removal of antibiotics are relatively scarce and not in sufficient depth. Only a few studies have further investigated the final fate of antibiotics in the immobilized bacteria system. In this study, a novel kind of OTC-degrading bacteria Mycolicibacterium sp. was immobilized on straw biochar and magnetic biochar, respectively. Magnetic biochar was proved to be a more satisfactory immobilization carrier due to its superior property and the advantage of easy recycling. Compared with free bacteria, immobilized bacteria had stronger environmental adaptability under different OTC concentrations, pH, and heavy metal ions. After 5 cycles, immobilized bacteria could still remove 71.8% of OTC, indicating that it had a stable recyclability. Besides, OTC in real swine wastewater was completely removed by immobilized bacteria within 2 days. The results of FTIR showed that bacteria were successfully immobilized on biochar and O-H, N-H, and C-N groups might be involved in the removal of OTC. The fate analysis indicated that OTC was removed by simultaneous adsorption and biodegradation, while biodegradation (92.8%) played a dominant role in the immobilized bacteria system. Meanwhile, the amount of adsorbed OTC (7.20%) was rather small, which could effectively decrease the secondary pollution of OTC. At last, new degradation pathways of OTC were proposed. This study provides an eco-friendly and effective approach to remedy OTC pollution in wastewater.

A review on the effects of discharging conventionally treated livestock waste to the environmental resistome

Globally, animal production has developed rapidly as a consequence of the ongoing population growth, to support food security. This has consequently led to an extensive use of antibiotics to promote growth and prevent diseases in animals. However, most antibiotics are not fully metabolized by these animals, leading to their excretion within urine and faeces, thus making these wastes a major reservoir of antibiotics residues, antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB) in the environment. Farmers normally depend on conventional treatment methods to mitigate the environmental impact of animal waste; however, these methods are not fully efficient to remove the environmental resistome. The present study reviewed the variability of residual antibiotics, ARB, as well as ARGs in the conventionally treated waste and assessed how discharging it could increase resistome in the receiving environments. Wherein, considering the efficiency and environmental safety, an addition of pre-treatments steps with these conventional treatment methods could enhance the removal of antibiotic resistance agents from livestock waste.

Key genes of electron transfer, the nitrogen cycle and tetracycline removal in bioelectrochemical systems

BACKGROUND

Soil microbial fuel cells (MFCs) can remove antibiotics and antibiotic resistance genes (ARGs) simultaneously, but their removal mechanism is unclear. In this study, metagenomic analysis was employed to reveal the functional genes involved in degradation, electron transfer and the nitrogen cycle in the soil MFC.

RESULTS

The results showed that the soil MFC effectively removed tetracycline in the overlapping area of the cathode and anode, which was 64% higher than that of the control. The ARGs abundance increased by 14% after tetracycline was added (54% of the amplified ARGs belonged to efflux pump genes), while the abundance decreased by 17% in the soil MFC. Five potential degraders of tetracycline were identified, especially the species Phenylobacterium zucineum, which could secrete the 4-hydroxyacetophenone monooxygenase encoded by EC 1.14.13.84 to catalyse deacylation or decarboxylation. Bacillus, Geobacter, Anaerolinea, Gemmatirosa kalamazoonesis and Steroidobacter denitrificans since ubiquinone reductase (encoded by EC 1.6.5.3), succinate dehydrogenase (EC 1.3.5.1), Coenzyme Q-cytochrome c reductase (EC 1.10.2.2), cytochrome-c oxidase (EC 1.9.3.1) and electron transfer flavoprotein-ubiquinone oxidoreductase (EC 1.5.5.1) served as complexes I, II, III, IV and ubiquinone, respectively, to accelerate electron transfer. Additionally, nitrogen metabolism-related gene abundance increased by 16% to support the microbial efficacy in the soil MFC, and especially EC 1.7.5.1, and coding the mutual conversion between nitrite and nitrate was obviously improved.

CONCLUSIONS

The soil MFC promoted functional bacterial growth, increased functional gene abundance (including nitrogen cycling, electron transfer, and biodegradation), and facilitated antibiotic and ARG removal. Therefore, soil MFCs have expansive prospects in the remediation of antibiotic-contaminated soil. This study provides insight into the biodegradation mechanism at the gene level in soil bioelectrochemical remediation.

Biochar-assisted degradation of oxytetracycline by Achromobacter denitrificans and underlying mechanisms

Contamination of the environment with large amounts of residual oxytetracycline (OTC) and the corresponding resistance genes poses a potential threat to natural ecosystems and human health. In this study, an effective OTC-degrading strain, identified as Achromobacter denitrificans OTC-F, was isolated from activated sludge. In the degradation experiment, the degradation rates of OTC in the degradation systems with and without biochar addition were 95.01-100% and 73.72-99.66%, respectively. Biochar promotes the biodegradation of OTC, particularly under extreme environmental conditions. Toxicity evaluation experiments showed that biochar reduced biotoxicity and increased the proportion of living cells by 17.36%. Additionally, biochar increased the activity of antioxidant enzymes by 34.1-91.0%. Metabolomic analysis revealed that biochar promoted the secretion of antioxidant substances such as glutathione and tetrahydrofolate, which effectively reduced oxidative stress induced by OTC. This study revealed the mechanism at the molecular level and provided new strategies for the bioremediation of OTC in the environment.

Immobilization of Bacillus Thuringiensis and applicability in removal of sulfamethazine from soil

Microbial degradation is considered an essential and promising treatment for sulfadimidine contamination of soil. To address the low colonization rates and inefficiencies of typical antibiotic-degrading bacteria, sulfamethazine (SM2)-degrading strain H38 is converted into immobilized bacteria in this study. Results show that the removal rate of SM2 by immobilized strain H38 reaches 98% at 36 h, whereas the removal rate of SM2 by free bacteria reaches 75.2% at 60 h. In addition, the immobilized bacteria H38 exhibits tolerance to a wide range of pH (5-9) and temperature (20 °C-40 °C). As the amount of inoculation increases and the initial concentration of SM2 decreases, the removal rate of SM2 by the immobilized strain H38 increases gradually. Laboratory soil remediation tests show that the immobilized strain H38 can remove 90.0% of SM2 from the soil on the 12th day, which exceeds the removal by free bacteria by 23.9% in the same period. Additionally, the results show that the immobilized strain H38 enhances the overall activity of microorganisms in SM2-contaminated soil. Compared with the SM2 only (control group containing no bacteria) and free bacterial treatment groups, the gene expression levels of ammonia-oxidizing archaea, ammonia-oxidizing bacteria, cbbLG, and cbbM increased significantly in the treatment group with immobilized strain H38. This study shows that immobilized strain H38 can reduce the effect of SM2 on soil ecology to a greater extent than free bacteria, while providing safe and effective remediation.

Multi-omic profiling of a novel activated sludge strain Sphingobacterium sp. WM1 reveals the mechanism of tetracycline biodegradation and its merits of potential application

As an emerging pollutant, the antibiotic tetracycline (TC) has been consistently detected in wastewater and activated sludge. Biodegradation represents a potentially crucial pathway to dissipate TC contamination. However, few efficient TC-degrading bacteria have been isolated and a comprehensive understanding of the molecular mechanisms underlying TC degradation is still lacking. In this study, a novel TC-degrading bacterium, designated as Sphingobacterium sp. WM1, was successfully isolated from activated sludge. Strain WM1 exhibited a remarkable performance in degrading 50 mg/L TC within 1 day under co-metabolic conditions. Genomic analysis of the strain WM1 unveiled the presence of three functional tetX genes. Unraveling the complex molecular mechanisms, transcriptome analysis highlighted the role of upregulated transmembrane transport and accelerated electron transport in facilitating TC degradation. Proteomics confirmed the up-regulation of proteins involved in cellular biosynthesis/metabolism and ribosomal processes. Crucially, the tetX gene-encoding protein showed a significant upregulation, indicating its role in TC degradation. Heterologous expression of the tetX gene resulted in TC dissipation from an initial 51.9 mg/L to 4.2 mg/L within 24 h. The degradation pathway encompassed TC hydroxylation, transforming into TP461 and subsequent metabolites, which effectively depleted TC's inhibitory activity. Notably, the tetX genes in strain WM1 showed limited potential for horizontal gene transfer. Collectively, strain WM1's potent TC degradation capacity signals a promise for enhancing TC clean-up strategies.

Characterization and removal mechanism of a novel enrofloxacin-degrading microorganism, Microbacterium proteolyticum GJEE142 capable of simultaneous removal of enrofloxacin, nitrogen and phosphorus

In the study, a novel ENR-degrading microorganism, Microbacterium proteolyticum GJEE142 was isolated from aquaculture wastewater for the first time. The ENR removal of strain GJEE142 was reliant upon the provision of limited additional carbon source, and was adaptative to low temperature (13 ℃) and high salinity (50‰). The ENR removal process, to which intracellular enzymes made more contributions, was implemented in three proposed pathways. During the removal process, oxidative stress response of strain GJEE142 was activated and the bacterial toxicity of ENR was decreased. Strain GJEE142 could also achieve the synchronous removal of ammonium, nitrite, nitrate and phosphorus with the nitrogen removal pathways of nitrate → nitrite → ammonium → glutamine → glutamate → glutamate metabolism and nitrate → nitrite → gaseous nitrogen. The phosphorus removal was implemented under complete aerobic conditions with the assistance of polyphosphate kinase and exopolyphosphatase. Genomic analysis provided corresponding genetic insights for deciphering removal mechanisms of ENR, nitrogen and phosphorus. ENR, nitrogen and phosphorus in both actual aquaculture wastewater and domestic wastewater could be desirably removed. Desirable adaptation, excellent performance and wide distribution will make strain GJEE142 the hopeful strain in wastewater treatment.

Comparative Metagenomic and Metatranscriptomic Analyses Reveal the Response of Black Soldier Fly (Hermetia illucens) Larvae Intestinal Microbes and Reduction Mechanisms to High Concentrations of Tetracycline

Black soldier fly (Hermetia illucens L) larvae (BSFL) possess remarkable antibiotic degradation abilities due to their robust intestinal microbiota. However, the response mechanism of BSFL intestinal microbes to the high concentration of antibiotic stress remains unclear. In this study, we investigated the shift in BSFL gut microbiome and the functional genes that respond to 1250 mg/kg of tetracycline via metagenomic and metatranscriptomic analysis, respectively. The bio-physiological phenotypes showed that the survival rate of BSFL was not affected by tetracycline, while the biomass and substrate consumption of BSFL was slightly reduced. Natural BSFL achieved a 20% higher tetracycline degradation rate than the germ-free BSFL after 8 days of rearing. Metagenomic and metatranscriptomic sequencing results revealed the differences between the entire and active microbiome. Metatranscriptomic analysis indicated that Enterococcus, Vagococcus, Providencia, and Paenalcaligenes were the active genera that responded to tetracycline. Furthermore, based on the active functional genes that responded to tetracycline pressure, the response mechanisms of BSFL intestinal microbes were speculated as follows: the Tet family that mediates the expression of efflux pumps expel tetracycline out of the microbes, while tetM and tetW release it from the ribosome. Eventually, tetracycline was degraded by deacetylases and novel enzymes. Overall, this study provides novel insights about the active intestinal microbes and their functional genes in insects responding to the high concentration of antibiotics.

Antimicrobial Transformation Products in the Aquatic Environment: Global Occurrence, Ecotoxicological Risks, and Potential of Antibiotic Resistance

The global spread of antimicrobial resistance (AMR) is concerning for the health of humans, animals, and the environment in a One Health perspective. Assessments of AMR and associated environmental hazards mostly focus on antimicrobial parent compounds, while largely overlooking their transformation products (TPs). This review lists antimicrobial TPs identified in surface water environments and examines their potential for AMR promotion, ecological risk, as well as human health and environmental hazards using in silico models. Our review also summarizes the key transformation compartments of TPs, related pathways for TPs reaching surface waters and methodologies for studying the fate of TPs. The 56 antimicrobial TPs covered by the review were prioritized via scoring and ranking of various risk and hazard parameters. Most data on occurrences to date have been reported in Europe, while little is known about antibiotic TPs in Africa, Central and South America, Asia, and Oceania. Occurrence data on antiviral TPs and other antibacterial TPs are even scarcer. We propose evaluation of structural similarity between parent compounds and TPs for TP risk assessment. We predicted a risk of AMR for 13 TPs, especially TPs of tetracyclines and macrolides. We estimated the ecotoxicological effect concentrations of TPs from the experimental effect data of the parent chemical for bacteria, algae and water fleas, scaled by potency differences predicted by quantitative structure-activity relationships (QSARs) for baseline toxicity and a scaling factor for structural similarity. Inclusion of TPs in mixtures with their parent increased the ecological risk quotient over the threshold of one for 7 of the 24 antimicrobials included in this analysis, while only one parent had a risk quotient above one. Thirteen TPs, from which 6 were macrolide TPs, posed a risk to at least one of the three tested species. There were 12/21 TPs identified that are likely to exhibit a similar or higher level of mutagenicity/carcinogenicity, respectively, than their parent compound, with tetracycline TPs often showing increased mutagenicity. Most TPs with increased carcinogenicity belonged to sulfonamides. Most of the TPs were predicted to be mobile but not bioaccumulative, and 14 were predicted to be persistent. The six highest-priority TPs originated from the tetracycline antibiotic family and antivirals. This review, and in particular our ranking of antimicrobial TPs of concern, can support authorities in planning related intervention strategies and source mitigation of antimicrobials toward a sustainable future.

Critical review of phytoremediation for the removal of antibiotics and antibiotic resistance genes in wastewater

Antibiotics in wastewater are a growing environmental concern. Increased prescription and consumption rates have resulted in higher antibiotic wastewater concentration. Conventional wastewater treatment methods are often ineffective at antibiotic removal. Given the environmental risk of antibiotics and associated antibiotic resistant genes (ARGs), finding methods of improving antibiotic removal from wastewater is of great importance. Phytoremediation of antibiotics in wastewater, facilitated through constructed wetlands, has been explored in a growing number of studies. To assess the removal efficiency and treatment mechanisms of plants and microorganisms within constructed wetlands for specific antibiotics of major antibiotic classes, the present review paper considered and evaluated data from the most recent published research on the topics of bench scale hydroponic, lab and pilot scale constructed wetland, and full scale constructed wetland antibiotic remediation. Additionally, microbial and enzymatic antibiotic degradation, antibiotic-ARG correlation, and plant effect on ARGs were considered. It is concluded from the present review that plants readily uptake sulfonamide, macrolide, tetracycline, and fluoroquinolone antibiotics and that constructed wetlands are an effective applied phytoremediation strategy for the removal of antibiotics from wastewater through the mechanisms of microbial biodegradation, root sorption, plant uptake, translocation, and metabolization. More research is needed to better understand the effect of plants on microbial community and ARGs. This paper serves as a synthesis of information that will help guide future research and applied use of constructed wetlands in the field antibiotic phytoremediation and wastewater treatment.

Enrichment of tetracycline-degrading bacterial consortia: Microbial community succession and degradation characteristics and mechanism

Tetracycline (TC) is an antibiotic that is recently found as an emerging pollutant with low biodegradability. Biodegradation shows great potential for TC dissipation. In this study, two TC-degrading microbial consortia (named SL and SI) were respectively enriched from activated sludge and soil. Bacterial diversity decreased in these finally enriched consortia compared with the original microbiota. Moreover, most ARGs quantified during the acclimation process became less abundant in the finally enriched microbial consortia. Microbial compositions of the two consortia as revealed by 16 S rRNA sequencing were similar to some extent, and the dominant genera Pseudomonas, Sphingobacterium, and Achromobacter were identified as the potential TC degraders. In addition, consortia SL and SI were capable of biodegrading TC (initial 50 mg/L) by 82.92% and 86.83% within 7 days, respectively. They could retain high degradation capabilities under a wide pH range (4-10) and at moderate/high temperatures (25-40 °C). Peptone with concentrations of 4-10 g/L could serve as a desirable primary growth substrate for consortia to remove TC through co-metabolism. A total of 16 possible intermediates including a novel biodegradation product TP245 were detected during TC degradation. Peroxidase genes, tetX-like genes and the enriched genes related to aromatic compound degradation as revealed by metagenomic sequencing were likely responsible for TC biodegradation.

Mesoporous Activated Biochar from Crab Shell with Enhanced Adsorption Performance for Tetracycline

In this study, three mesoporous-activated crab shell biochars were prepared by carbonation and chemical activation with KOH (K-CSB), H₃PO₄ (P-CSB), and KMnO₄ (M-CSB) to evaluate their tetracycline (TC) adsorption capacities. Characterization by SEM and a porosity analysis revealed that the K-CSB, P-CSB, and M-CSB possessed a puffy, mesoporous structure, with K-CSB exhibiting a larger specific surface area (1738 m²/g). FT-IR analysis revealed that abundant, surface ox-containing functional groups possessed by K-CSB, P-CSB, and M-CSB, such as -OH, C-O, and C=O, enhanced adsorption for TC, thereby enhancing their adsorption efficiency for TC. The maximum TC adsorption capacities of the K-CSB, P-CSB, and M-CSB were 380.92, 331.53, and 281.38 mg/g, respectively. The adsorption isotherms and kinetics data of the three TC adsorbents fit the Langmuir and pseudo-second-order model. The adsorption mechanism involved aperture filling, hydrogen bonding, electrostatic action, π-π EDA action, and complexation. As a low-cost and highly effective adsorbent for antibiotic wastewater treatment, activated crab shell biochar has enormous application potential.

Cultivation of algal-bacterial granular sludge and degradation characteristics of tetracycline

Due to the increasing use of antibiotics, tetracycline was frequently detected in wastewater. As a novel technology, algal-bacterial granular sludge process is expected to be widely used in wastewater treatment. However, the degradation effect of tetracycline by algal-bacterial granular sludge process and its degradation path is still unknown. In this study, mature and stable algal-bacterial granular sludge was cultured and the degradation of tetracycline by it was investigated. The results showed that the removal amount of 1-25 mg/L tetracycline by algal-bacterial granular sludge was 0.09-1.45 mg/g volatile suspended solids (VSS), in which the adsorption amount was 0.06-0.17 mg/g VSS and the degradation amount was 0.03-1.27 mg/g VSS. Tetracycline biosorption was dominant at its concentration of 1-3 mg/L, while biodegradation was predominant at 5-25 mg/L of tetracycline. At tetracycline concentration of 3-5 mg/L, the contribution of biosorption and biodegradation to tetracycline removal by algal-bacterial granular sludge process was almost equal. Algal-bacterial granular sludge could effectively degrade tetracycline through demethylation, dehydrogenation, deacylation, and deamination or their combination. In addition, the degradation products were nontoxic and hardly pose a threat to environmental health. The research results of this paper provide a solid theoretical basis for tetracycline removal by algal-bacterial granular sludge and a reference for the development of algal-bacterial granular sludge process for wastewater treatment in the presence of tetracycline. PRACTITIONER POINTS: Mature and stable algal-bacterial granular sludge was cultured. Tetracycline was removed by algal-bacterial granular sludge through biosorption and biodegradation. Algal-bacterial granular sludge could degrade tetracycline through demethylation, dehydrogenation, deacylation, and deamination or their combination. The degradation products were nontoxic.

Versatility of Stenotrophomonas maltophilia: Ecological roles of RND efflux pumps

S. maltophilia is a widely distributed bacterium found in natural, anthropized and clinical environments. The genome of this opportunistic pathogen of environmental origin includes a large number of genes encoding RND efflux pumps independently of the clinical or environmental origin of the strains. These pumps have been historically associated with the uptake of antibiotics and clinically relevant molecules because they confer resistance to many antibiotics. However, considering the environmental origin of S. maltophilia, the ecological role of these pumps needs to be clarified. RND efflux systems are highly conserved within bacteria and encountered both in pathogenic and non-pathogenic species. Moreover, their evolutionary origin, conservation and multiple copies in bacterial genomes suggest a primordial role in cellular functions and environmental adaptation. This review is aimed at elucidating the ecological role of S. maltophilia RND efflux pumps in the environmental context and providing an exhaustive description of the environmental niches of S. maltophilia. By looking at the substrates and functions of the pumps, we propose different involvements and roles according to the adaptation of the bacterium to various niches. We highlight that i°) regulatory mechanisms and inducer molecules help to understand the conditions leading to their expression, and ii°) association and functional redundancy of RND pumps and other efflux systems demonstrate their complex role within S. maltophilia cells. These observations emphasize that RND efflux pumps play a role in the versatility of S. maltophilia.

The Impact of Tetracycline Pollution on the Aquatic Environment and Removal Strategies

Antibacterial drugs are among the most commonly used medications in the world. Tetracycline is a widely used antibiotic for human and animal therapy due to its broad-spectrum activity, high effectiveness, and reasonable cost. The indications for treatment with tetracycline include pneumonia, bone and joint infections, infectious disorders of the skin, sexually transmitted and gastrointestinal infections. However, tetracycline has become a serious threat to the environment because of its overuse by humans and veterinarians and weak ability to degrade. Tetracycline is capable of accumulating along the food chain, causing toxicity to the microbial community, encouraging the development and spread of antibiotic resistance, creating threats to drinking and irrigation water, and disrupting microbial flora in the human intestine. It is essential to address the negative impact of tetracycline on the environment, as it causes ecological imbalance. Ineffective wastewater systems are among the main reasons for the increased antibiotic concentrations in aquatic sources. It is possible to degrade tetracycline by breaking it down into small molecules with less harmful or nonhazardous effects. A range of methods for physical, chemical, and biological degradation exists. The review will discuss the negative effects of tetracycline consumption on the aquatic environment and describe available removal methods.

The capability of chloramphenicol biotransformation of Klebsiella sp. YB1 under cadmium stress and its genome analysis

Co-contamination by antibiotics and heavy metal is common in the environment, however, there is scarce information about antibiotics biodegradation under heavy metals stress. In this study, Klebsiella sp. Strain YB1 was isolated which is capable of biodegrading chloramphenicol (CAP) with a biodegradation efficiency of 22.41% at an initial CAP of 10 mg L^-1 within 2 days. CAP biodegradation which fitted well with the first-order kinetics. YB1 still degrades CAP under Cd stress, however 10 mg L^-1 Cd inhibited CAP biodegradation by 15.1%. Biotransformation pathways remained the same under Cd stress, but two new products (Cmpd 19 and Cmpd 20) were identified. Five parallel metabolism pathways of CAP were proposed with/without Cd stress, including one novel pathway (pathway 5) that has not been reported before. In pathway 5, the initial reaction was oxidation of CAP by disruption of C-C bond at the side chain of C1 and C2 with the formation of 4-nitrobenzyl alcohol and CY7, then these intermediates were oxidized into p-nitrobenzoic acid and CY1, respectively. CAP acetyltransferase and nitroreductase and 2,3/4,5-dioxygenase may play an important role in CAP biodegradation through genome analysis and prediction. This study deepens our understanding of mechanism of antibiotic degradation under heavy metal stress in the environment.

Dynamics of microbial communities during biotransformation of nitrofurantoin

The purpose of this research was to investigate the biodegradation of nitrofurantoin (NFT), a typical nitrofuran antibiotic of potential carcinogenic properties, by two microbial communities derived from distinct environmental niches - mountain stream (NW) and seaport water (SS). The collected environmental samples represent the reserve of the protected area with no human intervention and the contaminated area that concentrates intense human activities. The structure, composition, and diversity of the communities were analyzed at three timepoints during NFT biodegradation. Comamonadaceae (43.2%) and Pseudomonadaceae (19.6%) were the most abundant families in the initial NW sample. The top families in the initial SS sample included Aeromonadaceae (31.4%) and Vibrionaceae (25.3%). The proportion of the most abundant families in both consortia was remarkably reduced in all samples treated with NFT. The biodiversity significantly increased in both consortia treated with NFT suggesting that NFT significantly alters community structure in the aquatic systems. In this study, NFT removal efficiency and transformation products were also studied. The biodegradation rate decreased with the increasing initial NFT concentration. Biodegradation followed similar pathways for both consortia and led to the formation of transformation products: 1-aminohydantoin, semicarbazide (SEM), and hydrazine (HYD). SEM and HYD were detected for the first time as NFT biotransformation products. This study demonstrates that the structure of the microbial community may be directly correlated with the presence of NFT. Enchanced biodiversity of the microbial community does not have to be correlated with increase in functional capacity, such as the ability to biodegradation because higher biodiversity corresponded to lower biodegradation. Our findings provide new insights into the effect of NFT contamination on aquatic microbiomes. The study also increases our understanding of the environmental impact of nitrofuran residues and their biodegradation.

Efficient Degradation of Tetracycline Antibiotics by Engineered Myoglobin with High Peroxidase Activity

Tetracyclines are one class of widely used antibiotics. Meanwhile, due to abuse and improper disposal, they are often detected in wastewater, which causes a series of environmental problems and poses a threat to human health and safety. As an efficient and environmentally friendly method, enzymatic catalysis has attracted much attention. In previous studies, we have designed an efficient peroxidase (F43Y/P88W/F138W Mb, termed YWW Mb) based on the protein scaffold of myoglobin (Mb), an O₂ carrier, by modifying the heme active center and introducing two Trp residues. In this study, we further applied it to degrade the tetracycline antibiotics. Both UV-Vis and HPLC studies showed that the triple mutant YWW Mb was able to catalyze the degradation of tetracycline, oxytetracycline, doxycycline, and chlortetracycline effectively, with a degradation rate of ~100%, ~98%, ~94%, and ~90%, respectively, within 5 min by using H₂O₂ as an oxidant. These activities are much higher than those of wild-type Mb and other heme enzymes such as manganese peroxidase. As further analyzed by UPLC-ESI-MS, we identified multiple degradation products and thus proposed possible degradation mechanisms. In addition, the toxicity of the products was analyzed by using in vitro antibacterial experiments of E. coli. Therefore, this study indicates that the engineered heme enzyme has potential applications for environmental remediation by degradation of tetracycline antibiotics.

Effect of live and inactivated Chlamydomonas reinhardtii on the removal of tetracycline in aquatic environments

With the development of medical drugs, the widely used tetracycline has brought many adverse effects on the ecosystem and human health. Tetracycline pollution of water environment is becoming more and more serious, and has become an emerging environmental problem. As single celled organisms, microalgae are not only model organisms for risk assessment of aquatic ecosystems, but also can efficiently purify sewage. Microalgae-mediated pollutant remediation has attracted more and more attention from researchers. In this paper, Chlamydomonas reinhardtii (C. reinhardtii) was used to remove tetracycline in aqueous solution, and the removal efficiency and mechanism of microalgae on tetracycline were studied. The results showed that the removal rates of tetracycline by active and inactivated microalgae at a density of 5 × 10⁶ cells·mL^-1 were 81.9% and 89.8%, respectively. C. reinhardtii removed tetracycline through biosorption and nonmetabolic processes. Microalgal cell supernatant and hydroxyl radicals could significantly promote the removal of tetracycline. The positively charged tetracycline was electrostatically adsorbed on the microalgae surface and extracellular polymeric substances. Microalgae biomass can promote the production of ROS and enhance the ability of microalgae to remove tetracycline.

Natural detoxification of antibiotics in the environment: A one health perspective

The extended concept of one health integrates biological, geological, and chemical (bio-geo-chemical) components. Anthropogenic antibiotics are constantly and increasingly released into the soil and water environments. The fate of these drugs in the thin Earth space ("critical zone") where the biosphere is placed determines the effect of antimicrobial agents on the microbiosphere, which can potentially alter the composition of the ecosystem and lead to the selection of antibiotic-resistant microorganisms including animal and human pathogens. However, soil and water environments are highly heterogeneous in their local composition; thus the permanence and activity of antibiotics. This is a case of "molecular ecology": antibiotic molecules are adsorbed and eventually inactivated by interacting with biotic and abiotic molecules that are present at different concentrations in different places. There are poorly explored aspects of the pharmacodynamics (PD, biological action) and pharmacokinetics (PK, rates of decay) of antibiotics in water and soil environments. In this review, we explore the various biotic and abiotic factors contributing to antibiotic detoxification in the environment. These factors range from spontaneous degradation to the detoxifying effects produced by clay minerals (forming geochemical platforms with degradative reactions influenced by light, metals, or pH), charcoal, natural organic matter (including cellulose and chitin), biodegradation by bacterial populations and complex bacterial consortia (including "bacterial subsistence"; in other words, microbes taking antibiotics as nutrients), by planktonic microalgae, fungi, plant removal and degradation, or sequestration by living and dead cells (necrobiome detoxification). Many of these processes occur in particulated material where bacteria from various origins (microbiota coalescence) might also attach (microbiotic particles), thereby determining the antibiotic environmental PK/PD and influencing the local selection of antibiotic resistant bacteria. The exploration of this complex field requires a multidisciplinary effort in developing the molecular ecology of antibiotics, but could result in a much more precise determination of the one health hazards of antibiotic production and release.

Self-Assembly 2D Ti3C2/g-C3N4 MXene Heterojunction for Highly Efficient Photocatalytic Degradation of Tetracycline in Visible Wavelength Range

An ultrathin 2D Ti₃C₂/g-C₃N₄ MXene (2D-TC/CN) heterojunction was synthesized, using a facile self-assembly method; the perfect microscopic-morphology and the lattice structure presented in the sample with a 2 wt% content of Ti₃C₂ were observed by the field-emission scanning electron microscopy (SEM) and transmission electron microscope (TEM). The optimized sample (2-TC/CN) exhibited excellent performance in degrading the tetracycline (TC), and the degradation rate reached 93.93% in the conditions of 20 mg/L, 50 mL of tetracycline within 60 min. Except for the increased specific-surface area, investigated by UV-vis diffuse reflectance spectra (UV-vis DRS) and X-ray photoelectron microscopy (XPS) valence spectra, the significantly enhanced photocatalytic activity of the 2-TC/CN could also be ascribed to the formation of Ti-N bonds between Ti₃C₂ and g-C₃N₄ nanosheets, which reduced the width of the band gap through adjusting the position of the valence band, thus resulting in the broadened light-absorption. Furthermore, the facilitated electron transmission was also proved by time-resolved photoluminescence (TRPL) and electrochemical impedance spectroscopy (EIS), which is effective in improving the quantum efficiency of photo-generated electrons. In addition, the resulting radical-capture experiment suggested that superoxide radicals have the greatest influence on photodegradation performance, with the photodegradation rate of TC reducing from 93.16% to 32.08% after the capture of superoxide radicals, which can be attributed to the production of superoxide radicals only, by the 2-TC/CN composites with a high conduction-band value (-0.62 eV). These facilely designed 2D Ti₃C₂/g-C₃N₄ composites possess great application potential for the photodegradation of tetracycline and other antibiotics.

Unraveling the key driving factors involved in cometabolism enhanced aerobic degradation of tetracycline in wastewater

Cometabolism has shown great potential in increasing the engineering feasibility of microalgae-based biotechnologies for the aerobic treatment of antibiotics-polluted wastewaters. Yet, the underlying mechanisms involved in improved microalgal performance remain unknown. In this study, we incorporated transcriptomics, gene network analysis, and enzymatic activities with cometabolic pathways of tetracycline (TC) by Chlorella pyrenoidosa to identify the key driving factors. The results demonstrated that cometabolism constructed a metabolic enzymes-photosynthetic machinery to improve the electron transport chain and activities of catalytic enzymes, which resulted in subsequent 100% removal of TC. Coupling formation dynamics of the intermediates with roles of identified metabolic enzymes, degradation of TC can be induced by de/hydroxylation, de/hydrogenation, bond-cleavage, decarboxylation, and deamination. Evaluation of 18 antibiotics' removal in reclaimed water showed cometabolism decreased the total concentrations of these antibiotics from 495.54 ng L^-1 to 221.80 ng L^-1. Our findings not only highlight the application potential of cometabolism in increasing engineering feasibility of microalgal degradation of antibiotics from wastewaters, but also provide the unique insights into unraveling the "black-box" of cometabolisms in aerobic biodegradation.

Artificial microbial consortium producing oxidases enhanced the biotransformation efficiencies of multi-antibiotics

Antibiotic mixtures in the environment result in the development of bacterial strains with resistance against multiple antibiotics. Oxidases are versatile that can bio-remove antibiotics. Various laccases (LACs), manganese peroxidases (MNPs), and versatile peroxidase (VP) were reconstructed in Pichia pastoris. For the single antibiotics, over 95.0% sulfamethoxazole within 48 h, tetracycline, oxytetracycline, and norfloxacin within 96 h were bio-removed by recombinant VP with α-signal peptide, respectively. In a mixture of the four antibiotics, 80.2% tetracycline and 95.6% oxytetracycline were bio-removed by recombinant MNP2 with native signal peptide (NSP) within 8 h, whereas < 80.0% sulfamethoxazole was bio-removed within 72 h, indicating that signal peptides significantly impacted removal efficiencies of antibiotic mixtures. Regarding mediators for LACs, 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) resulted in better removal efficiencies of multi-antibiotic mixtures than 1-hydroxybenzotriazole or syringaldehyde. Furthermore, artificial microbial consortia (AMC) producing LAC2 and MNP2 with NSP significantly improved bio-removal efficiency of sulfamethoxazole (95.5%) in four-antibiotic mixtures within 48 h. Tetracycline and oxytetracycline were completely bio-removed by AMC within 48 and 72 h, respectively, indicating that AMC accelerated sulfamethoxazole, tetracycline, and oxytetracycline bio-removals. Additionally, transformation pathways of each antibiotic by recombinant oxidases were proposed. Taken together, this work provides a new strategy to simultaneously remove antibiotic mixtures by AMC.

Environmental risks caused by livestock and poultry farms to the soils: Comparison of swine, chicken, and cattle farms

The lack of treatment systems for pollutants in family-livestock and poultry sites results in large amounts of untreated manure and urine being directly discharged to environment. The risks from veterinary antibiotic (VA) and heavy metal (HM) exposure in the rural environment require further research. In this investigation, 221 samples (feed, manure, surface soil, soil profiles, water, and plant) were collected from 41 livestock and poultry farms (swine, chichen, and cattle). Copper (Cu), zinc (Zn), oxytetracycline (OTC), and enrofloxacin (ENR) were frequently detected in the samples. Metals and VAs in sandy loam soils were more inclined to migrate to deep layers than those in loam soils. Copper and Zn in the polluted soils mainly existed in available forms, which facilitated their migration to deep soil layers. In this study, OTC was also observed to migrate more easily to deeper soil layers than ENR due to its relatively high pKa value. Eighteen antibiotic resistance genes (ARGs) and 5 metal resistance genes (MRGs) along with one mobile genetic element (MGE) occurred in the soils at 80 cm depth. Luteimonas, Clostridium_sensu_stricto_1, and Rhodanobacter were dominant genera detected in the soil samples from different sites, which might increase migration of ARGs or degradation of VAs. An ecological risk assessment suggested that VAs posed threats to the growth of Triticum aestivum L, Cucumis sativus L, and Brassiaca chinensis L. Remediation techniques including biochar/modified biochar, anaerobic digestion, and manure composting should be developed urgently for joint HM and VA pollution.

Slower antibiotics degradation and higher resistance genes enrichment in plastisphere

Microplastics (MPs) are increasingly entering the urban aquatic ecosystems, and the environmental significance and health risks of plastisphere, a special biofilm on MPs, have received widespread attention. In this study, MPs of polylactic acid (PLA) and polyvinyl chloride (PVC) and quartzite were incubated in an urban water environment, and the tetracycline (TC) degradation ability was compared. Approximatedly 24% of TC biodegraded in 28 d in the water-quartzite system, which is significantly higher than that in the water-PLA (17.3%) and water-PVC systems (16.7%). Re-incubation of microorganisms in biofilms affirmed that quartzite biofilm has a higher TC degradation capacity than the plastisphere. According to high-throughput sequencing of 16S rRNA and metagenomic analysis, quartzite biofilm contained more abundant potential TC degrading bacteria, genes related to TC degradation (eutG, aceE, and DLAT), and metabolic pathways related to TC degradation. An oligotrophic environment on the quartzite surface might lead to the higher metabolic capacity of quartzite biofilm for unconventional carbons, e.g., TC. It is also found that, compared with quartzite biofilm, the distinct microbes in the plastisphere carried more antibiotic resistance genes (ARGs). Higher affinity of MPs surface to antibiotics may lead to higher antibiotics stress on the plastisphere, which further amplify the carrying capacity for ARGs of microorganisms in the plastisphere. Compared to the nondegradable PVC MPs, surface of the biodegradable PLA plastics harbored significantly higher amounts of biomass and ARGs. Compared to the mineral particles, the capability of plastisphere has lower ability to degrade unconventional carbon sources such as the refractory organic pollutants, due to the abundance of carbon sources (adsorbed organic carbon and endogenous organic carbon) on the MPs surface. Meanwhile, the stronger adsorption capacity for pollutants also leads to higher pollutant stress (such as antibiotic stress) in plastisphere, which in turn affects the microbiological characteristics of the plastisphere itself, such as carrying more ARGs.