Intervention of antimicrobial peptide usage on antimicrobial resistance in aquaculture

Fabulous combination therapy: Synergistic antibiotic inhibition of aquatic antibiotic-resistant bacteria via membrane damage and DNA binding by novel nano antimicrobial peptide C-I20

Aquatic microbiota' antibiotic resistance undermines traditional treatment efficacy, posing a severe threat to sustainable water environment. Our study addresses this challenge through a fantastic approach involving novel nano antimicrobial peptide C-I20 and antibiotics. Antibacterial tests demonstrated that C-I20 effectively combated both standard and aquatic pathogenic resistant strains. C-I20 killed drug-resistant bacteria by disrupting membrane structure and binding to DNA. C-I20 bound to DNA, forming precipitates susceptible to rapid degradation by trypsin and DNase I. When combined with chloramphenicol, florfenicol, ampicillin, or enrofloxacin, C-I20 exhibited remarkably higher inhibitory rates against bacteria compared to individual use of C-I20 or antibiotics alone. Continuous passage analysis revealed that co-administration of C-I20 with chloramphenicol, florfenicol, ampicillin, and enrofloxacin delays the emergence and progression of antibiotic resistance. This combination therapy was proved to be highly effective, notably reducing tissue bacterial loads and pathological changes. Evaluation in an Aeromonas hydrophila infection model showed the lowest morbidity rate and bacterial loading in the C-I20 combined with ampicillin group. Antimicrobial susceptibility analysis confirmed that C-I20 supplementation markedly suppresses ampicillin-induced intestinal resistant bacteria. In conclusion, C-I20 in conjunction with antibiotic therapy effectively inhibits infection and drug-resistant bacterial development, offering a promising strategy for managing drug-resistant bacteria in aquatic animals.

Removal of Fe2+ in coastal aquaculture source water by manganese ores: Batch experiments and breakthrough curve modeling

Excessive Fe2+ in coastal aquaculture source water will seriously affect the aquaculture development. This study used manganese sand to investigate the removal potential and mechanism of Fe2+ in coastal aquaculture source water by column experiments. The pseudo-first-order kinetic model could better describe Fe2+ removal process with R2 in the range of 0.9451-0.9911. More than 99.7% of Fe2+ could be removed within 120 min while the removal rate (k) was positively affected by low initial concentration of Fe2+, high temperature, and low pH. Logistic growth (S-shaped growth) model could better fit the concentration variation of Fe2+ in the effluent of the column (R2>0.99). The Fe2 breakthrough curve could be fitted by Bohart-Adams, Yoon-Nelson, and Thomas models (R2>0.95). Smooth slices with irregular shapes existed on the surface of manganese sand after the reaction while Fe content increased significantly on the surface of manganese sand after the column experiment. Moreover, FeO (OH) was mainly formed on the surface of manganese sand after the reaction. PRACTITIONER POINTS: Fe2+ in coastal aquaculture source water could be removed by manganese ores. The pseudo-first-order kinetic model better described the Fe2+ removal process. FeO (OH) was mainly formed on the surface of manganese sand after the reaction.

Heterologous expression of frog antimicrobial peptide Odorranain-C1 in Pichia pastoris: Biological characteristics and its application in food preservation

To reduce food spoilage and deterioration caused by microbial contamination, antimicrobial peptides (AMPs) have gradually gained attention as a biological preservative. Odorranain-C1 is an α-helical cationic antimicrobial peptide extracted from the skin of frogs with broad-spectrum antimicrobial activity. In this study, we achieved the expression of Odorranain-C1 in Pichia pastoris (P. pastoris) (also known as Komagataella phaffii) by employing DNA recombination technology. The recombinant Odorranain-C1 showed broad-spectrum antibacterial activity and displayed a minimum inhibitory concentration within the range of 8-12 μg.mL-1. Meanwhile, Odorranain-C1 exhibited superior stability and lower hemolytic activity. Mechanistically, Odorranain-C1 disrupted the bacterial membrane's integrity, ultimately causing membrane rupture and subsequent cell death. In tilapia fillets preservation, Odorranain-C1 inhibited the total colony growth and pH variations, while also reducing the production of total volatile basic nitrogen (TVB-N) and thiobarbituric acid (TBA). In conclusion, these studies demonstrated the efficient recombinant expression of Odorranain-C1 in P. pastoris, highlighting its promising utilization in food preservation.

Antimicrobial peptides: An alternative to antibiotic for mitigating the risks of Antibiotic resistance in aquaculture

The utilization of antibiotics increases the prevalence of antibiotic resistance genes (ARGs) in various matrices and poses the potential risk of ARG transmission, garnering global attention. Antimicrobial peptides (AMPs) represent a promising novel category of antimicrobials that may address the urgent issue of antibiotic resistance. Here, a zebrafish cultivation assay in which zebrafish were fed a diet supplemented with AMP (Cecropin A) or antibiotics was conducted to determine the effects of the intervention on the microorganisms and antibiotic resistance spectrum in zebrafish gut samples. Cecropin A treatment decreased the α-diversity of the microbiota. Moreover, NMDS (nonmetric multidimensional scaling) results revealed that the β-diversity in the microbiota was more similar between the control (CK) and Cecropin A samples than between the antibiotic treatment groups. The absolute quantity of ARGs in the AMP treatment was less than that observed in the antibiotic treatment. The findings indicated that FFCH7168, Chitinibacter and Cetobacterium were the most significant biomarkers detected in the CK, Cecropin A and antibiotic treatments, respectively. Although the use of antibiotics notably enhanced the occurrence of multidrug-resistant bacteria, the application of Cecropin A did not lead to this phenomenon. The results indicated that the application of AMPs can effectively manage and control ARGs in aquaculture.

Challenges in computational discovery of bioactive peptides in 'omics data

Peptides have a plethora of activities in biological systems that can potentially be exploited biotechnologically. Several peptides are used clinically, as well as in industry and agriculture. The increase in available 'omics data has recently provided a large opportunity for mining novel enzymes, biosynthetic gene clusters, and molecules. While these data primarily consist of DNA sequences, other types of data provide important complementary information. Due to their size, the approaches proven successful at discovering novel proteins of canonical size cannot be naïvely applied to the discovery of peptides. Peptides can be encoded directly in the genome as short open reading frames (smORFs), or they can be derived from larger proteins by proteolysis. Both of these peptide classes pose challenges as simple methods for their prediction result in large numbers of false positives. Similarly, functional annotation of larger proteins, traditionally based on sequence similarity to infer orthology and then transferring functions between characterized proteins and uncharacterized ones, cannot be applied for short sequences. The use of these techniques is much more limited and alternative approaches based on machine learning are used instead. Here, we review the limitations of traditional methods as well as the alternative methods that have recently been developed for discovering novel bioactive peptides with a focus on prokaryotic genomes and metagenomes.

A systematic review of antibiotic resistance driven by metal-based nanoparticles: Mechanisms and a call for risk mitigation

Elevations in antibiotic resistance genes (ARGs) are due not only to the antibiotic burden, but also to numerous environmental pressures (e.g., pesticides, metal ions, or psychotropic pharmaceuticals), which have led to an international public health emergency. Metal-based nanoparticles (MNPs) poison bacteria while propelling nanoresistance at ambient or sub-lethal concentrations, acting as a wide spectrum germicidal agent. Awareness of MNPs driven antibiotic resistance has created a surge of investigation into the molecule mechanisms of evolving and spreading environmental antibiotic resistome. Co-occurrence of MNPs resistance and antibiotic resistance emerge in environmental pathogens and benign microbes may entail a crucial outcome for human health. In this review we expound on the systematic mechanism of ARGs proliferation under the stress of MNPs, including reactive oxygen species (ROS) induced mutation, horizontal gene transfer (HGT) relevant genes regulation, nano-property, quorum sensing, and biofilm formation and highlighting on the momentous contribution of nanoparticle released ion. As antibiotic resistance pattern alteration is closely knit with the mediate activation of nanoparticle in water, soil, manure, or sludge habitats, we have proposed a virulence and evolution based antibiotic resistance risk assessment strategy for MNP contaminated areas and discussed practicable approaches that call for risk management in critical environmental compartments.

Occurrence characteristics and influencing factors of antibiotic resistance genes in rural groundwater in Henan Province

This study determined the antibiotic-resistant gene (ARG) contents of 34 groundwater samples in Henan Province collected from September to October 2022, then assessed the roles of both water quality parameters and intI1 in ARG propagation in groundwater. The results show that there existed universal ARG pollution in groundwater, and sulfonamides-, β-lactem-, and tetracycline-resistance genes were the most prevalent gene types during the time. Sul1 contributed the majority proportion of the total resistance genes (TARGs). The prevalence of ESBLs gene blaTEM and the occurrence of Carbapenems resistant gene blaOXA-1 suggests the pollution of high-risk ARGs in groundwater demands more attention. IntI1 is prevalent and had a significantly positive correlation with almost 50% ARGs, indicating its contribution to ARG propagation in groundwater. Well types contribute little to ARG propagation in rural groundwater of Henan, which means the protective facilities established by the local government for public wells can effectively prevent contamination from exogenous ARGs. However, the economic level has no impact on the abundance of ARGs in rural groundwater, which suggests the local government should pay greater attention to investment in controlling ARG pollution in Henan rural areas.

Spatial distribution and seasonal variation of trace hazardous elements contamination in the coastal environment

Groundwater is the second largest water source for daily consumption, only next to surface water resources. Groundwater has been extensively investigated for its pollution level in urban areas. The groundwater quality assessments in industrial areas associated with every urban landscape are still lacking. In order to examine the spatial distribution characteristics, pollution levels, and sources of trace metals in the densely populated Chennai coastal region of Tamilnadu, India, physicochemical parameters and trace element concentrations have been determined in groundwater. 55 groundwater samples from Tamil Nadu's coastal region were collected and analyzed for physicochemical parameters such as pH, (EC), (TDS), and (TH) during the pre-monsoon (June 2015) and post-monsoon (January 2016) seasons. We used trace elements and analyzed them in this study (Mg, Zn, Pb, Ni, Co, Cu, Cr, and Fe). Furthermore, anthropogenic input from industries and power plants exacerbates the pollution of Ni, Mg, Fe, and Mn. Due to evaporites and anthropogenic input, samples with excessive salinity, total hardness, and water quality are considered unsuitable for irrigation or drinking. The results demonstrated that seasonal, geogenic, and anthropogenic influences all have a significant impact on the heterogeneous chemistry of groundwater.

Antimicrobial Hydrogels: Potential Materials for Medical Application

Microbial infections based on drug-resistant pathogenic organisms following surgery or trauma and uncontrolled bleeding are the main causes of increased mortality from trauma worldwide. The prevalence of drug-resistant pathogens has led to a significant increase in medical costs and poses a great threat to the normal life of people. This is an important issue in the field of biomedicine, and the emergence of new antimicrobial materials hydrogels holds great promise for solving this problem. Hydrogel is an important material with good biocompatibility, water absorption, oxygen permeability, adhesion, degradation, self-healing, corrosion resistance, and controlled release of drugs as well as structural diversity. Bacteria-disturbing hydrogels have important applications in the direction of surgical treatment, wound dressing, medical device coating, and tissue engineering. This paper reviews the classification of antimicrobial hydrogels, the current status of research, and the potential of antimicrobial hydrogels for one application in biomedicine, and analyzes the current research of hydrogels in biomedical applications from five aspects: metal-loaded hydrogels, drug-loaded hydrogels, carbon-material-loaded hydrogels, hydrogels with fixed antimicrobial activity and biological antimicrobial hydrogels, and provides an outlook on the high antimicrobial activity, biodegradability, biocompatibility, injectability, clinical applicability and future development prospects of hydrogels in this field.

Hydrogeochemical evaluation with emphasis on nitrate and fluoride in urban and rural drinking water resources in western Isfahan province, central Iran

Nitrate (NO3-) and fluoride (F-) are two major potential contaminants found in the groundwater of Iran. These contaminants are highly dangerous to humans if consumed more than the safe limit prescribed by the WHO. Therefore, in this study, the urban and rural drinking water resources of Isfahan province (central Iran) were investigated to evaluate the quality of groundwater from the perspective of NO3- and F-. The calculated saturation index (SI) shows that the majority of samples are mainly undersaturated or in equilibrium with respect to potential minerals. The most likely interpretation for undersaturation with respect to most minerals is either that the minerals are not present if they are reactive or if they are present, then they are not reactive. This study reveals that the majority of the groundwater samples belong to the Ca-Mg-HCO3 water type. Further, in this study, potential physicochemical variables have been used to calculate entropy weighted water quality index (EWQI). The EWQI reveals that the majority of the groundwater in the area is of good quality. Results show that the water chemistry in the area is largely governed by the water-rock interaction. This study based on large data sets reveals that the majority of drinking water resources are uncontaminated by F-. However, the groundwater is found to be largely contaminated by NO3-. The bivariate plot suggests that the unscientific farming practices and overuse of manures and fertilizers are largely responsible for high content of NO3-. Therefore, emphasis should be given on the cost-effective environmentally friendly fertilizers. The findings from this study will aid the governing authorities and concerned stakeholders to understand the hydrogeochemical evolution of groundwater in this region. The results will help formulate policies in the area for sustainable water supply.

Effects of freeze-thaw dynamics and microplastics on the distribution of antibiotic resistance genes in soil aggregates

This is the first study investigating the effects of freeze-thaw (FT) and microplastics (MPs) on the distribution of antibiotic resistance genes (ARGs) in soil aggregates (i.e., soil basic constituent and functional unit) via microcosm experiments. The results showed that FT significantly increased the total relative abundance of target ARGs in different aggregates due to the increase in intI1 and ARG host bacteria. However, polyethylene MPs (PE-MPs) hindered the increase in ARG abundance caused by FT. The host bacteria carrying ARGs and intI1 varied with aggregate size, and the highest number of hosts was observed in micro-aggregates (<0.25 mm). FT and MPs altered host bacteria abundance by affecting aggregate physicochemical properties and bacterial community and enhanced multiple antibiotic resistance via vertical gene transfer. Although the dominant factors affecting ARGs varied with aggregate size, intI1 was a co-dominant factor in various-sized aggregates. Furthermore, other than ARGs, FT, PE-MPs, and their integration promoted the proliferation of human pathogenic bacteria in aggregates. These findings suggested that FT and its integration with MPs significantly affected ARG distribution in soil aggregates. They amplified antibiotic resistance environmental risks, contributing to a profound understanding of soil antibiotic resistance in the boreal region.

Applications of antimicrobial peptides (AMPs) as an alternative to antibiotic use in aquaculture – A mini-review

The use of antibiotics for the control of infections has not only been banned by FDA for use in food-producing animals, but also several countries have prohibited their use in aquaculture because of several reasons such as the occurrence of antibiotic-tolerant microorganisms, accumulation of antibiotic residues in fish and shrimp flesh, and aquatic environmental effluence concerns. These issues have led researchers and aquaculture scientists to conduct several studies to find antibiotic alternatives. Numerous substitutes have been evaluated, such as probiotics, synbiotics, prebiotics, postbiotics, phytogenics, essential oils, and several others. Results show that these supplements demonstrate proven efficacy in enhancing immune responses, reducing mortalities resulting from experimental infections, and reducing antibiotic usage in medicated aquafeed. Nonetheless, using antimicrobial peptides (AMPs) to control fish diseases and as antibiotic alternatives is a promising and interesting research topic. AMPs are a vital class of small peptides that could stimulate the innate immune system against challenging pathogens and also possess significant potent defensive responses against a variety of infectious and noninfectious pathogenic agents, including bacteria, parasites, fungi, and viruses. Regarding their source origin, AMPs can be classified into six main types: mammalian-, amphibian-, insect-, aquatic-, plant-, and microorganism-derived AMPs. On account of their unique structure, they can display an essential function in therapeutic strategies against infectious diseases affecting fish and shrimp. Reports showed several kinds of AMPs had a wide spectrum of antimicrobial properties. These effects are besides their prominent immunostimulatory functions. Thus, they may be considered a functional alternative to antibiotics in aquaculture. This article provides information on the current knowledge about the modes of action, sources, classification, functions, and potential applications for the development of aquatic animal health. The information included in this context will be valuable to enhance the sustainability of aquaculture.

A Review of Antibiotics, Antibiotic Resistant Bacteria, and Resistance Genes in Aquaculture: Occurrence, Contamination, and Transmission

Antibiotics are commonly used to prevent and control diseases in aquaculture. However, long-term/overuse of antibiotics not only leaves residues but results in the development of antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs). Antibiotics, ARB, and ARGs are widespread in aquaculture ecosystems. However, their impacts and interaction mechanisms in biotic and abiotic media remain to be clarified. In this paper, we summarized the detection methods, present status, and transfer mechanisms of antibiotics, ARB, and ARGs in water, sediment, and aquaculture organisms. Currently, the dominant methods of detecting antibiotics, ARB, and ARGs are UPLC-MS/MS, 16S rRNA sequencing, and metagenomics, respectively. Tetracyclines, macrolides, fluoroquinolones, and sulfonamides are most frequently detected in aquaculture. Generally, antibiotic concentrations and ARG abundance in sediment are much higher than those in water. Yet, no obvious patterns in the category of antibiotics or ARB are present in organisms or the environment. The key mechanisms of resistance to antibiotics in bacteria include reducing the cell membrane permeability, enhancing antibiotic efflux, and structural changes in antibiotic target proteins. Moreover, horizontal transfer is a major pathway for ARGs transfer, including conjugation, transformation, transduction, and vesiculation. Identifying, quantifying, and summarizing the interactions and transmission mechanisms of antibiotics, ARGs, and ARB would provide useful information for future disease diagnosis and scientific management in aquaculture.

The prevalence of potential pathogens in ballast water and sediments of oceangoing vessels and implications for management

Ballast water and sediments can serve as prominent vectors for the widespread dispersal of pathogens between geographically distant areas. However, information regarding the diversity and distribution of the bacterial pathogens in ballast water and sediments is highly limited. In this study, using high-throughput sequencing and quantitative PCR, we investigated the composition and abundance of potential pathogens, and their associations with indicator microorganisms. We accordingly detected 48 potential bacterial pathogens in the assessed ballast water and sediments, among which there were significant differences in the compositions and abundances of pathogenic bacterial communities characterizing ballast water and sediments. Rhodococcus erythropolis, Bacteroides vulgatus, and Vibrio campbellii were identified as predominant pathogens in ballast water, whereas Pseudomonas stutzeri, Mycobacterium paragordonae, and Bacillus anthracis predominated in ballast sediments. Bacteroidetes, Vibrio alginolyticus, Vibrio parahaemolyticus, and Escherichia coli were generally detected with median values of 8.54 × 10³-1.22 × 10⁷ gene copies (GC)/100 mL and 1.16 × 10⁷-3.97 × 10⁹ GC/100 g in ballast water and sediments, respectively. Notably, the concentrations of Shigella sp., Staphylococcus aureus, and V. alginolyticus were significantly higher in ballast sediments than in the water. In addition, our findings tend to confirm that the indicator species specified by the International Maritime Organization (IMO) might underestimate the pathogen risk in the ballast water and sediments, as these bacteria were unable to predict some potential pathogens assessed in this study. In summary, this study provides a comprehensive insight into the spectrum of the potential pathogens that transferred by ship ballast tanks and emphasizes the need for the implementation of IMO convention on ballast sediment management.

Photothermal Hydrogels for Promoting Infected Wound Healing

Photothermal therapies (PTT), with spatiotemporally controllable antibacterial capabilities without inducing resistance, have shown encouraging prospects in the field of infected wound treatments. As an important platform for PTT, photothermal hydrogels exhibit attractive advantages in the field of infected wound treatment due to their excellent biochemical properties and have been intensively explored in recent years. This review summarizes the progress of the photothermal hydrogels for promoting infected wound healing. Three major elements of photothermal hydrogels, i.e., photothermal materials, hydrogel matrix, and construction methods, are introduced. Furthermore, different strategies of photothermal hydrogels in the treatment of infected wounds are summarized. Finally, the challenges and prospects in the clinical treatment of photothermal hydrogels are discussed.

Adsorption of nonylphenol on coastal saline soil: Will microplastics play a great role?

Microplastics widely exist in diverse matrices to become important hosts of pollutants. Little information regarding adsorption of emerging contaminants on coastal saline soils influenced by co-existing microplastics is available. Thus, the adsorption behaviors of nonylphenol (NP) on coastal saline soil influenced by microplastics were discussed. Polyvinyl chloride (PVC, 4.7 mm), polyethylene (4.85 mm), and polypropylene (4.51 mm) with addition dose of 10% were used to discuss the effect of microplastic type on adsorption of NP by coastal saline soil while PVC samples with size of 4.7 mm and 0.11 mm were used to explore the effect of microplastic size on NP adsorption. The NP adsorption capacity of the saline soil containing 10% of PVC (4.7 mm) was twice that of soil without PVC. Smaller-size PVC (0.11 mm) with addition amount of 10% enhanced the NP adsorption capacity of the coastal saline soil by 117% to reach 8.91 μg g^-1. The desorption capacity of NP on saline soil decreased from 40% to 30% of total adsorption capacity with co-existing PVC. Adsorption/desorption kinetics of NP on coastal saline soil with PVC microplastics could be well explained by pseudo second order model while Freundlich model could better fit the isotherm data of NP adsorption/desorption to show possible occurrence of the multiple-layer adsorption. This study will provide new information regarding the environmental behaviors of typical emerging contaminants on coastal saline soil containing microplastics.

A high-precision prediction for spatiotemporal distribution and risk assessment of antibiotics in an urban watershed using a hydrodynamic model

A methodology for the high-precision prediction and risk assessment of antibiotics at the watershed scale was established. Antibiotic emission inventory and attenuation processes were integrated into the MIKE 11 model to predict the spatiotemporal distribution of norfloxacin, ofloxacin, enrofloxacin, erythromycin, roxithromycin, and sulfamethoxazole in the Nanfei River watershed, China. Considering the variations in antibiotic removal in sewage treatment plants, manure composting, and lagoon systems, the high, medium, and low removal efficiencies of selected antibiotics across China were obtained and used as the best, expected, and worst scenarios, respectively, to evaluate the uncertainty of antibiotic emissions. The predicted concentrations were comparable to antibiotic measurements after flow calibration. The prediction results showed that the highest concentration exposures were mainly concentrated in urban areas with a dense population. Flow variations controlled the temporal distribution characteristics of antibiotics via the dilution effect, and the concentrations of antibiotics in the dry season were 3.1 times higher than those in the wet season. The median concentrations of norfloxacin and erythromycin ranged from 111.36 ng/L to 592.33 ng/L and 106.63 ng/L to 563.01 ng/L, respectively, which both posed a high risk to cyanobacteria and a medium risk to spreading antibiotic resistance. Scenario analysis further demonstrated that high removal efficiencies of these antibiotics can considerably reduce the potential ecotoxicity risks and bacterial resistance selection. The developed methodology for predicting the distribution and risk of antibiotics was suitable for the risk assessment and control strategy of human- and livestock-sourced pollutants.

Enhanced direct interspecies electron transfer and methane production during anaerobic digestion of fat, oil, and grease by coupling carbon-based conductive materials and exogenous hydrogen

To investigate the combination of carbon-based conductive materials and exogenous hydrogen (EH2) on methane recovery from fat, oil, and grease (FOG), granular activated carbon (GAC) and carbon cloth (CC) were chosen to collaborate with EH2, resulting in increased methane production by 59 % and 84 %, respectively. Further digestion of long chain fatty acids (LCFAs) confirms that enhanced direct interspecies electron transfer (DIET) was achieved in the reactors with GAC/CC + EH2 than those with GAC/CC only. Other evidences (such as increased microbial population and rapid degradation of volatile fatty acids) were found to support the role of GAC/CC + EH2 in promotion of DIET. Significant change of microbial community was observed using GAC/CC + EH2, which was mainly attributed to the enrichment of electrogenic species (such as Spirochaetaceae, Syntrophomonas palmitatica, and Methanosaeta), leading to some changes in metabolic pathways during acidogenesis and methanogenesis. Together, enhanced DIET was achieved by GAC/CC + EH2, thus improving the methane recovery from FOG.

Catalytic ozonation of antibiotics by using Mg(OH)2 nanosheet with dot-sheet hierarchical structure as novel nanoconfined catalyst

Antibiotic pollution has caused important concern for international and national sustainability. Catalytic ozonation is a quick and efficient technique to remove contaminants in aquatic environment. This study firstly developed a nanosheet-growth technique for synthesizing Li-doped Mg(OH)₂ with dot-sheet hierarchical structure as catalyst to ozonize antibiotics. Metronidazole could be totally removed through ozonation catalyzed by Li-doped Mg(OH)₂ in 10 min. Approximately 97% of metronidazole was eliminated in 10 min even the catalyst was used for 4 times. Reaction rate constant of Li-doped Mg(OH)₂ treatment was about 3.45 times that of nano-Mg(OH)₂ treatment, illustrating that the dot-sheet hierarchical structure of Li-doped Mg(OH)₂ exhibited nano-confinement effect on the catalytic ozonation. Approximately 70.4% of metronidazole was mineralized by catalytic ozonation using Li-doped Mg(OH)₂. Temperature of 25 °C was more suitable for catalytic ozonation of metronidazole by Li-doped Mg(OH)₂. Ions generally inhibited the catalytic ozonation of metronidazole while only 0.005 mol L^-1 of Cl^- slightly enhanced the ozonation rate, illustrating complicated mechanisms existed for ozonation of metronidazole catalyzed by Li-doped Mg(OH)₂. The possible mechanisms of the ozonation of metronidazole using Li-doped Mg(OH)₂ included direct ozonation and ozonation catalyzed by radical ·O₂^-, reactive oxygen species ¹O₂ and intermediate (H₂O₂). The synthesized Mg(OH)₂ nanosheet with dot-sheet hierarchical structure is a novel nanoconfined material with excellent reusability and catalytic performance.

Seasonal distribution of antibiotic resistance genes under the influence of land-ocean interaction in a semi-enclosed bay

The irrational use of antibiotics has given rise to the proliferation of antibiotic resistance genes (ARGs) in coastal bays. There were few reports on the seasonal distribution of ARGs under the influence of land-ocean interaction in coastal bay. This work studied the seasonal and spatial proliferation of ARGs under the influences of land-ocean interaction in the Sishili Bay. Ten ARGs including tetB, tetG, tetX, sul1, sul2, qnrA, qnrB, qnrS, ermF, ermT and class 1 integron-integrase gene (intI1) were detected and quantified. The relative abundances of intI1 and most of ARGs were in orders of magnitude of 1 × 10^-7-2 copies/16S rRNA copies. The abundances of total ARGs in autumn and summer were much higher than those in the other seasons. Estuary, port and aquaculture farms were important reservoirs of ARGs in the bay. The nutrient levels in coastal water were positively associated with most of the ARGs and intI1, indicating that the water quality was an important driver of ARGs and their transmission. The land-based discharge and seawater stratification were proved to be the dominant driving factors for the seasonal distribution of ARGs in the coastal bay. The land-based discharge and seawater stratification were enhanced from spring to summer, which led to the sharp increase in ARGs in the surface water of the bay.

Water quality evaluation and ecological-health risk assessment on trace elements in surface water of the northeastern Qinghai-Tibet Plateau

The Qinghai-Tibet Plateau is a unique area with water sources for approximately 40 % of the population in the world. Water resources and water quality are closely associated with ecological security and human health. Fifty-one trace elements in surface water samples (n = 40) were measured, and water quality, health and ecological risks were assessed. Trace elements showed significant variations in different surface water bodies in the study area. Concentrations of minor elements were relatively high in saline and salt lakes while those of REEs varied from 0.05 to 33.62 μg/L with an average value of 3.80 μg/L. The Nemerow pollution index (NP) values of trace elements ranged from 0.08 to 3.48, with an average value of 0.36 in rivers, fresh lakes and reservoir water samples; The heavy metal pollution index (HPI) values ranged from 3.70 to 21.18, indicating that most samples were within the critical limit; The heavy metal evaluation index (HEI) values and degree of contamination (DC) values indicated a free pollution status. The water quality index (WQI) values showed that 96 % of the samples belonged to excellent status in rivers, fresh lakes and reservoir water samples. More attention should be given to the Cr, Zn and Hg in the study area according to potential ecological risk assessment. Hazard quotients for residential children in 30 sites exceed 1.0 with maximal value of 10.97, suggesting the high non-carcinogenic risks for children in the study area. U, Zr and Cr for the ingestion pathway, Cr and U for the dermal pathway were primary contributors to the total health risk. Carcinogenic risk values of trace elements for residential and recreational receptors were in the range of 3.20 × 10^-5-7.38 × 10^-3 and 8.62 × 10^-6-3.63 × 10^-3, respectively. The carcinogenic risk values of Cr in surface water were higher than the target risk of 1 × 10^-4, while the carcinogenic risk values of As were below the target risk. The results of this study provided information on trace elements for human health protection and water management in the northeastern Qinghai-Tibet Plateau.

Two Foreign Antimicrobial Peptides Expressed in the Chloroplast of Porphyridium purpureum Possessed Antibacterial Properties

To solve the problem of antibiotic abuse in aquaculture and to utilize the application potential of antimicrobial peptides (AMPs), a chloroplast transformation system of Porphyridium purpureum was successfully constructed for effectively expressing two exogenous AMPs. The endogenous fragments of 16S rDNA/trnA-23S rDNA were used as flanking fragments for the homologous recombination in the chloroplast genome. Two AMPs encoded by the transformation vector were controlled by the native promoter psbB in a polycistron. The plasmids were transferred into P. purpureum via particle bombardment and the transformation vectors were screened using phosphinothricin (bar), a dominant selection marker under the control of the psbA promoter. Subsequently, in the positive transformed colonies, the exogenous fragments were found to be inserted in the flanking fragments directionally as expected and two foreign AMPs were successfully obtained. Finally, two exogenous peptides with antibacterial properties were obtained from the transformed strain. The two AMPs expressed by the transformed strain were shown to have similar inhibitory effects to antibiotics by inhibition tests. This suggested that AMPs can be introduced into aquaculture using baited microalgae, providing new ideas and ways to solve a series of aquaculture diseases caused by bacteria.

Quantification and Evaluation of Grey Water Footprint in Yantai

Problems such as water scarcity and pollution frequently occur in coastal zones. This study investigated the grey water footprint and the sustainability and intensity of grey water footprint in Yantai between 2014 and 2019 by taking both surface water and groundwater into consideration. The research results indicated that the Yantai grey water footprint firstly increased and then decreased between 2014 and 2019. The lowest grey water footprint in 2019 was 744 million m3. The agricultural grey water footprint accounted for a large proportion of the total grey water footprint. Although the sustainability of grey water footprint fluctuates in Yantai, it maintains well. The Yantai grey footprint intensity gradually decreased to <10 m3/10,000 CNY. The economic benefit of grey water footprint and utilization efficiency of water resources have been improved yearly. The quality of the water environment in Yantai has also been improved. The research of this paper provides some useful information for water resources protection and sustainable utilization in coastal cities.

Variation of Water Quality in Ningxia Section of the Yellow River in Recent 5 Years

The Yellow River is very important for human health and social development in China to require good water quality. This study selected the Ningxia section of the Yellow River as the study area to investigate the water quality variation in 2016–2020. A total of 9 water quality parameters were monitored, and 8 parameters including pH, dissolved oxygen, biological oxygen demand, chemical oxygen demand, total phosphate, fluoride, ammonia-nitrogen, and permanganate index were in the range of Class II standard requirement. Dissolved oxygen concentrations ranged from 7.5 to 9.4 mg/L. However, total nitrogen concentrations in 2018–2020 ranged from 1.87 to 2.8 mg/L to cause the pollution. Both the Nemerow index method and the contamination degree method showed that total nitrogen with high concentration exerted the water pollution. Principal component analysis also proved this. Stricter environmental management strategies for controlling total nitrogen should be taken in the future. The findings provided some useful information for water pollution of the Ningxia section of the Yellow River.