Antibiotic Resistance Genes Contamination Research Articles

Municipal-treated wastewater as a practical alternative to conventional rice irrigation: Effects on antibiotic resistance genes, virulence factors and human bacterial pathogens in soil, and responses of rice grain quality

Reuse of municipal-treated wastewater for agricultural irrigation is becoming increasingly prevalent due to growing demand and decline in freshwater supplies. However, the microbial contamination profile, including antibiotic resistance genes (ARGs), virulence factors (VFs), and human bacterial pathogens (HBPs) in agricultural soil irrigated with municipal-treated wastewater for paddy cultivation, was unknown. Here, metagenomic analysis was applied to provide a systematic insight into the resistome, VFs and HBPs in paddy soils irrigated with municipal-treated wastewater. The obtained results revealed that the residual antibiotics in municipal-treated wastewater has an impact on the antibiotic resistome by increasing both the total number and abundance of ARGs. Furthermore, it was found that sul1 could serve as a potential risk indicator for assessing ARG contamination. VFs, core HBP abundance, and dangerous pathogens remain unaffected by municipal-treated wastewater irrigation for paddy. The good coexistence patterns of ARGs-HBPs and ARGs-VFs demonstrated the presence of resistant pathogenic bacteria. The network analysis revealed that ARGs-bearing Legionella pneumophila, Mycobacterium marinum, Bordetella pertussis, Staphylococcus aureus, and Pseudomonas aeruginosa might be ranked as high-risk HBPs. Additionally, our investigation also demonstrated that reuse of municipal-treated wastewater for agricultural irrigation had no detrimental effects on rice plant growth and grain quality. This study was the first to investigate the response of VFs and HBPs in paddy soil under long-term municipal-treated wastewater irrigation. The obtained results provide a scientific basis for the safe application of municipal-treated wastewater.

Pollution status and spatial distribution of antibiotic resistance genes in urban surface water and surrounding soil media

The pollution of urban rivers by antibiotic resistance genes (ARGs) is affected by the production of antibiotics and the activities of residents in the regions, posing a threat to the health of the population around the regions. A detailed investigation of the spread of ARGs in urban rivers and the surrounding soil media provides both data support and basic framework for tracking the spread and for the elimination of ARGs. In this study, real-time fluorescence quantitative PCR (qPCR) was used to investigate the contamination status and spatial distribution patterns of ARGs around the entire basin of urban river, namely the Minxin river, and the city ring water system in Shijiazhuang, China. The contamination of ARGs in midstream and downstream of the Minxin river was more severe. No obviously spatial distribution differences were found in the soil samples. Water bodies are more susceptible to human activities than soil. It was identified that sul1, sul2, and blaSHV were the dominant genes of the ARGs. Significant correlations exist between ARGs and int1 and tnpA-IS4. Mobile genetic elements (MGEs) play a key role in the horizontal gene transfer of ARGs, facilitating their spread and dispersal among different species. This work revealed the geospatial characteristics of the distribution of ARGs in urban river basins, concluding that the production and living activities could accelerate the spread and diffusion of ARGs in urban river environments, and that an attention should be given to the use control and discharge of antibiotics.

Evolution and distribution of antibiotic resistance genes in submerged macrophytes and biofilm systems: From seasonal monitoring to mesocosm experiments

The aquatic ecosystem has been extensively investigated as a hotspot for the spread of antibiotic resistance genes (ARGs); yet, the evolution and distribution of ARGs profiles in submerged macrophytes biofilms and surrounding water remained unclear. In this study, the dynamic distribution and seasonal variations of microbial communities and ARGs profiles were investigated, alongside their assembly processes and mutual interactions. Bacitracin and multidrug resistance genes were predominant, constituting more than 60% of the total ARGs abundance. The deterministic processes (<65%), influenced by the physicochemical properties of the river environment, governed the assembly and composition of ARGs profiles, exhibiting significant seasonal variation. The peak diversity (21 types) and abundance (0.316 copy ratios) of ARGs were detected during the summer. Proteobacteria and Actinobacteria were the dominant bacterial phyla, accounting for 38.41–85.50% and 4.03–27.09% of the microbial community, respectively. Furthermore, Proteobacteria, especially genera such as Acinetobacter, Burkholderia, and Pseudomonas, with various resistance sequences, were the primary carriers of multiple ARGs. Notably, the genetic exchanges between biofilms and surrounding water facilitated the further propagation of high-risk ARGs, posing greater ecological risks. Redundancy analysis indicated that the total nitrogen and temperature in water determined the fate of pathogenic-resistant species. These findings provided theoretical support for the mitigation of ARGs contamination in aquatic environments.

Metagenomic profiling uncovers microbiota and antibiotic resistance patterns across human, chicken, pig fecal, and soil environments

The ongoing and progressive evolution of antibiotic resistance presents escalating challenges for the clinical management and prevention of bacterial infections. Understanding the makeup of resistance genomes and accurately quantifying the current abundance of antibiotic resistance genes (ARGs) are crucial for assessing the threat of antimicrobial resistance (AMR) to public health. This comprehensive study investigated the distribution and diversity of bacterial community composition, ARGs, and virulence factors (VFs) across human, chicken, pig fecal, and soil microbiomes in various provinces of China. As a result, multidrug resistance was identified across all samples. Core ARGs primarily related to multidrug, MLS (Macrolides-Lincosamide-Streptogramins), and tetracycline resistance were characterized. A significant correlation between ARGs and bacterial taxa was observed, especially in soil samples. Probiotic strains such as Lactobacillus harbored ARGs, potentially contributing to the dissemination of antibiotic resistance. We screened subsets of ARGs from samples from different sources as indicators to assess the level of ARGs contamination in samples, with high accuracy. These results underline the complex relationship between microbial communities, resistance mechanisms, and environmental factors, emphasizing the importance of continued research and monitoring to better understand these dynamics.

Occurrence and distribution of antibiotic resistance genes in urban rivers with black-odor water of Harbin, China

Antibiotic resistance gene contamination in polluted rivers remains a widely acknowledged environmental issue. This study focused on investigating the contamination conditions of antibiotic resistance genes (ARGs) in Harbin’s urban black-odor rivers, specifically Dongfeng Ditch and Hejia Ditch. The research employed a SmartChip Real-Time PCR System to explore the types, abundance, and distribution of ARGs in diverse habitats, such as surface water and sediment. Additionally, the study examined the correlation of ARGs with mobile genetic elements (MGEs) and various environmental factors. It was found that antibiotic resistance genes were prevalent in both water and sediment within the black-odor ditches. The dominant types of ARGs identified included aminoglycoside, sulfonamide, multidrug-resistant, and β-lactam ARGs. Notably, the top four ARGs, in terms of relative abundance, were sul1, fox5, qacEdelta1-01 and aadA1. Most categories of ARGs have significant positive connections with MGEs, indicating that the enrichment and spreading of ARGs in rivers are closely related to MGEs. Based on the correlation analysis, it is found that environmental factors such as dissolved oxygen (DO), ammonia nitrogen (NH4–N), and phosphate (PO4–P) played a substantial role in influencing the variations observed in ARGs. By employing a risk assessment framework based on the human association, host pathogenicity, and mobility of ARGs, the identification of seven high-risk ARGs was achieved. In addition, it is important to assess the environmental risk of ARGs from multiple perspectives (abundance,detection rateand mobility). This study provides a significant reference regarding the presence of ARGs contamination in urban inland black-odor rivers, essential for assessing the health risks associated with ARGs and devising strategies to mitigate the threat of antibiotic resistance.

Dominant microbiome iteration and antibiotic resistance genes propagation way dictate the antibiotic resistance genes contamination degree in soil-plant system

The enrichment of antibiotic resistance genes (ARGs) in crops harvested in antibiotics and ARGs contaminated soils has brought concerns for the global public health. Existing studies on ARGs contamination in antibiotic contaminated soil-plant system may be independent and unclarified to elucidate ARGs distribution in such system. This work managed to explain the distributions of ARGs in soil-wheat system where soils were collected from tetracycline polluted farmland and wheat grew for 90 days under four antibiotic conditions by adding no antibiotics, sulfamethoxazole (SMZ), oxytetracycline (OTC) and ciprofloxacin (CIP). Two sulfonamide resistance genes (SRGs) and three tetracycline resistance genes (TRGs) were detected in background soil and assigned to ARGs whose propagations relying on horizontal gene transfer and long-term tetracycline exposure, respectively. Wheat planting dramatically reduced the TRGs abundances by 5–50 times under four conditions because TRGs hosts were outcompeted by the microbiota iteration shock induced by the recruitment of plant probiotics and pathogens. Although SRGs hosts also underwent this shock, emerging SRGs hosts, mainly nitrogen fixation bacteria, were created by intI1 mediated horizontal gene transfer. Then SRGs abundances were not reduced but instead increased as emerging SRGs hosts became the dominant microbes in rhizosphere soil. SMZ stress particularly enriched SRGs by 6–22 times. Both TRGs and SRGs were accumulated in wheat roots and leaves, but owing to intI1 facilitation, SRGs bioaccumulations extremely exceeded TRGs. The invasion of nitrogen fixation bacteria carrying SRGs may also contribute to SRGs bioaccumulation. Consequently, we recapped a theory integrating ARGs propagation way, rhizospheric microbiota iteration and antibiotic stress to comprehend ARGs contamination in soil-plant system conducted in this and published works.

Contamination Characteristics，Detection Methods，and Control Methods of Antibiotic Resistance in Pharmaceutical Wastewater

Pharmaceutical industry wastewater contains a large number of emerging pollutants such as antibiotics， antibiotic resistant bacteria （ARBs）， and antibiotic resistance genes （ARGs）. The present biological water treatment processes cannot effectively remove these pollutants. Eventually， they are discharged into various water bodies or penetrate into soil with the effluent， causing environmental pollution and affecting human health. Therefore， exploring the pollution characteristics of antibiotics， ARBs， and ARGs in pharmaceutical wastewater and knowing the methods to detect and control antibiotic resistance pollution in wastewater are crucial for reducing the contamination of antibiotics and ARGs and assessing the ecological risks of antibiotic resistance. Aiming at the problem of antibiotic resistance pollution in a pharmaceutical wastewater treatment plant （PWWTPs）， the pollution status of antibiotics， ARBs， and ARGs in pharmaceutical wastewater was discussed. Different assessment methods of antibiotic resistance in pharmaceutical wastewater were summarized. Finally， the wastewater treatment technologies commonly used to remove antibiotics and ARGs in PWWTPs were summarized in order to provide a theoretical basis for the ecological risk assessment and scientific control of antibiotics and ARGs in the environment.

Investigating the antibiotic resistance genes and their potential risks in the megacity water environment: A case study of Shenzhen Bay Basin, China

Antibiotic resistance genes (ARGs) constitute emerging pollutants and pose serious risks to public health. Anthropogenic activities are recognized as the main driver of ARG dissemination in coastal regions. However, the distribution and dissemination of ARGs in Shenzhen Bay Basin, a typical megacity water environment, have been poorly investigated. Here, we comprehensively profiled ARGs in Shenzhen Bay Basin using metagenomic approaches, and estimated their associated health risks. ARG profiles varied greatly among different sampling locations with total abundance ranging from 2.79 × 10−2 (Shenzhen Bay sediment) to 1.04 (hospital sewage) copies per 16S rRNA gene copy, and 45.4% of them were located on plasmid-like sequences. Sewage treatment plants effluent and the corresponding tributary rivers were identified as the main sources of ARG contamination in Shenzhen Bay. Mobilizable plasmids and complete integrons carrying various ARGs probably participated in the dissemination of ARGs in Shenzhen Bay Basin. Additionally, 19 subtypes were assigned as high-risk ARGs (Rank I), and numerous ARGs were identified in potential human-associated pathogens, such as Burkholderiaceae, Rhodocyclaceae, Vibrionaceae, Pseudomonadaceae, and Aeromonadaceae. Overall, Shenzhen Bay represented a higher level of ARG risk than the ocean environment based on quantitative risk assessment. This study deepened our understanding of the ARGs and the associated risks in the megacity water environment.

Differentiation of environment and wastewater treatment plants by core antibiotic resistance genes and aadA2 as indicators in South Korea

Antibiotic resistance is reportedly disseminated from wastewater treatment plants (WWTPs) into aquatic environments. In this study, it was hypothesized that discharge of effluent from WWTPs may influence resistome of the adjacent aquatic environment. Thus, we aimed at investigation of resistome in WWTPs and receiving waters, to observe the dynamics of resistome and to determine the indicators for consistent comparison of contamination level. In this study, twenty-seven samples of upstreams (n = 9), downstreams (n = 9), and effluents (n = 9) samples from nine WWTPs located in the Nakdong and Yeongsan Rivers, South Korea, were collected for four years, and a total of 343 antibiotic resistance genes (ARGs) were quantitatively amplified using SmartChip analysis. The five core ARGs (aadA, aadA2, aadA5, strB, and sul1) were commonly detected in all samples. Three (aadA, aadA2, aadA5) of the five core ARGs were significantly more abundant in the effluent than in the aquatic environment. Interestingly, the water sources of the aquatic environments and effluents could be differentiated based on the abundance of the five core ARGs. The decision-making tree model supported the classification of the two water sources: aquatic environments and effluents. Taken together, considering the ubiquitous presence of the five ARGs with significantly different abundance between water sources, core ARGs including aadA2 are recommended as indicator genes to monitor ARGs contamination by employing quantitative analysis in South Korea. Determination of indicators would help consistently evaluate contamination level by ARGs.

Mass-immigration shapes the antibiotic resistome of wastewater treatment plants

Wastewater treatment plants (WWTPs) are the hotspots for the spread of antibiotic resistance genes (ARGs) into the environment. Nevertheless, a comprehensive assessment of the city-level and short-term daily (inter-day) variations of ARG profiles in the whole process (influent-INF, activated sludge-AS and effluent-EF) of WWTPs is still lacking. Here, 285 ARGs and ten mobile gene elements were monitored in seven WWTPs in Xiamen for seven days via high-throughput qPCR. The average daily load of ARGs to WWTPs was about 1.32 × 1020 copies/d, and a total of 1.56 × 1018 copies/d was discharged to the environment across the entire city. Stochastic processes were the main force determining the assembly of ARG communities during sampling campaign, with their relative importance ranked in the order of INF > EFF > AS. There're little daily variations in ARG richness, abundance, β-diversity composition as well as assembly mechanisms. The results of SourceTracker, variation partitioning analysis, and hierarchical partitioning analysis indicated that bacteria and ARGs from upstream treatment processes played an increasingly dominant role in shaping ARG communities in AS and EFF, respectively, suggesting the importance of mass-immigration of bacteria and ARGs from the source on ARG transport in wastewater treatment processes. This emphasizes the need to revise the way we mitigate ARG contamination but focus on the source of ARGs in urban wastewater.

Candidate biomarkers of antibiotic resistance for the monitoring of wastewater and the downstream environment

Urban wastewater treatment plants (UWTPs) are essential for reducing the pollutants load and protecting water bodies. However, wastewater catchment areas and UWTPs emit continuously antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs), with recognized impacts on the downstream environments. Recently, the European Commission recommended to monitor antibiotic resistance in UWTPs serving more than 100 000 population equivalents. Antibiotic resistance monitoring in environmental samples can be challenging. The expected complexity of these systems can jeopardize the interpretation capacity regarding, for instance, wastewater treatment efficiency, impacts of environmental contamination, or risks due to human exposure. Simplified monitoring frameworks will be essential for the successful implementation of analytical procedures, data analysis, and data sharing. This study aimed to test a set of biomarkers representative of ARG contamination, selected based on their frequent human association and, simultaneously, rare presence in pristine environments. In addition to the 16S rRNA gene, ten potential biomarkers (intI1, sul1, ermB, ermF, aph(3′’)-Ib, qacEΔ1, uidA, mefC, tetX, and crAssphage) were monitored in DNA extracts (n = 116) from raw wastewater, activated sludge, treated wastewater, and surface water (upstream and downstream of UWTPs) samples collected in the Czech Republic, Denmark, Israel, the Netherlands, and Portugal. Each biomarker was sensitive enough to measure decreases (on average by up to 2.5 log-units gene copy/mL) from raw wastewater to surface water, with variations in the same order of magnitude as for the 16S rRNA gene. The use of the 10 biomarkers allowed the typing of water samples whose origin or quality could be predicted in a blind test. The results show that, based on appropriate biomarkers, qPCR can be used for a cost-effective and technically accessible approach to monitoring wastewater and the downstream environment.

Spatio-temporal distribution and dynamics of antibiotic resistance genes in a water-diversion lake, China

The distribution and dynamics of antibiotic resistance genes (ARGs) in water-diversion lakes are poorly understood. In this study, two comparative in situ investigations of ARG profiles targeting water diversion (DP) and non-diversion periods (NDP) were conducted in Luoma Lake, a vital transfer node for the eastern route of the South-to-North Water Diversion Project in China. The results demonstrated significant spatiotemporal variations in ARG contamination and notable differences in the co-occurrence patterns of ARGs and bacterial communities between DP and NDP. Correlations among ARGs with the 16 S rRNA, and mobile genetic elements indicate that horizontal gene transfer (HGT) and vertical gene transfer (VGT) in NDP, but only HGT in DP, were the primary mechanisms of ARG proliferation and spread, implying that water diversion could be an essential control of the transfer pattern of ARGs in a lake environment. The null model analysis indicated that stochastic processes, with predominant driver of ecological drift in the lake mainly drove the assembly of ARGs. Partial least squares structural equation modeling was developed to analyze the causal effects of the factors in shaping ARG dynamics and identify the major driving forces in the DP and NDP.

Effect of fertilizer type on antibiotic resistance genes by reshaping the bacterial community and soil properties

Conventional and bio-organic fertilizers play an important role in maintaining soil health and promoting crop growth. However, the effect of organic fertilizers on the prevalence of antibiotic resistance genes (ARGs) in the vegetable cropping system has been largely overlooked. In this study, we investigated the impacts of soil properties and biotic factors on ARG profiles by analyzing ARG and bacterial communities in vegetable copping soils with a long-term history of manure and bio-organic fertilizer application. The ARG abundance in the soil was significantly increased by 116% with manure application compared to synthetic NPK fertilizer application. This finding was corroborated by our meta-analysis that the longer the duration of manure application, the greater the response of increased soil ARG abundance. However, bio-organic fertilizers containing Trichoderma spp. Significantly reduced ARG contamination by 31% compared to manure application. About half of the ARG variation was explained by changes in bacterial abundance and structure, followed by soil properties. The mitigation of ARG by Trichoderma spp. Is achieved by altering the structure of the bacterial community and weakening the close association between bacteria and ARG prevalence. Taken together, these findings shed light on the contribution of bio-organic fertilizers in mitigating ARG contamination in agricultural soils, which can help manage the ecological risk posed by ARG inputs associated with manure application.

Implications of vermicompost on antibiotic resistance in tropical agricultural soils – A study in Hainan Island, China

The contamination of antibiotic resistance genes (ARGs) associated with animal manure fertilization have attracted a global concern. Vermicompost has been widely popularized as an eco-friendly alternative to recycle animal manure on Hainan Island, China. However, the effects of vermicompost application on ARG spread and environmental fate in tropical agricultural soils remains undefined. Herein, the spatial prevalence and vertical behavior of ARGs in the soil profiles of vermicompost-applied agricultural regions were explored by a large-scale survey across Hainan Island. The results showed that although vermicompost application marginally enhanced the load of ARG pollution in the soil in Hainan, the ARGs derived from vermicompost did not eventually accumulate in the soil profile. The increase rate of ARGs in 40–60 cm soil layer was only 0.0015 % compared with that of unfertilized soil. Interestingly, vermicompost application reduced the abundance of high-risk ARGs, such as blaNDM and blaampC, by approximately one order of magnitude. Vermicompost was also observed to increase the abundance of beneficial bacteria, like Clostridium, and decrease those of Acidobacteriae, Planctomycetes and Verrucomicrobiae, which caused changes in the potential host bacteria of soil ARGs. Mobile genetic elements were further proven to be an essential factor that regulated the vertical dynamics of ARGs in vermicomposted soil, with a direct influence coefficient of 0.9975. This study demonstrated that the controllable risk associated with vermicompost application provided useful information to effectively reduce the threat of ARGs and promote the development of sustainable agriculture on Hainan Island.

Mitigation effects and microbial mechanism of two ecological earthworms on the uptake of chlortetracycline and antibiotic resistance genes in lettuce

The contamination of greenhouse vegetable soils with antibiotics and antibiotic resistance genes (ARGs), caused by the application of livestock and poultry manure, is a prominent environmental problem. In this study, the effects of two ecological earthworms (endogeic Metaphire guillelmi and epigeic Eisenia fetida) on the accumulation and transfer of chlortetracycline (CTC) and ARGs in a soil–lettuce system were studied via pot experiments. The results revealed that earthworm application accelerated the removal of the CTC from the soil and lettuce roots and leaves, with the CTC content reducing by 11.7–22.8 %, 15.7–36.1 %, and 8.93–19.6 % compared with that of the control, respectively. Both earthworms significantly reduced the CTC uptake by lettuce roots from the soil (P < 0.05) but did not change the CTC transfer efficiency from the roots to leaves. The high-throughput quantitative PCR results showed that the relative abundance of ARGs in the soil and lettuce roots and leaves decreased by 22.4–27.0 %, 25.1–44.1 %, and 24.4–25.4 %, respectively, with the application of earthworms. Earthworm addition decreased the interspecific bacterial interactions and the relative abundance of mobile genetic elements (MGEs), which helped reduce the dissemination of ARGs. Furthermore, some indigenous soil antibiotic degraders (Pseudomonas, Flavobacterium, Sphingobium, and Microbacterium) were stimulated by the earthworms. The results of redundancy analysis indicated that the bacterial community composition, CTC residues, and MGEs were the main parameters affecting the distribution of ARGs, accounting for 91.1 % of the total distribution. In addition, the bacterial function prediction results showed that the addition of earthworms reduced the abundance of some pathogenic bacteria in the system. Overall, our findings imply that earthworm application can substantially reduce the accumulation and transmission risk of antibiotics and ARGs in soil–lettuce systems, providing a cost-effective soil bioremediation practice for addressing antibiotic and ARGs contamination to guarantee the safety of vegetables and human health.

Land-derived wastewater facilitates antibiotic resistance contamination in marine sediment of semi-closed bay: A case study in Jiaozhou Bay, China

The emergence of antibiotic resistance is a severe threat to public health. There are few studies on the effects of sewage discharge on antibiotics and antibiotic resistance genes (ARGs) contamination in Jiaozhou Bay sediment. Herein, a total of 281 ARG subtypes, 10 mobile genetic elements (MGEs), 10 antibiotics and bacterial communities in marine sediments from Jiaozhou Bay were characterized. Similar bacterial community structures and ARG profiles were identified between the various sampling sites inside the bay, which were both dominated by multidrug and (fluoro)quinolone resistance genes and harbored lower relative abundances of ARGs than those in the sampling sites near the bay exit. Compared with antibiotics and MGEs, bacterial community composition was a more important driver of ARG diversity and geographic distribution. The abundance of pathogens carrying genetic information increased dramatically in southern Jiaozhou Bay is affected by sewage discharge, which indicating that wastewater discharge facilitated ARG contamination of marine sediments. This study highlights the risk of disseminating antibiotic resistance-influencing factors from treated wastewater discharge into marine environment there is an urgent need to optimize or improve wastewater treatment processes to enhance the removal of antibiotics and ARGs. This study has necessary implications for filling the gap in information on antibiotic resistance in Jiaozhou Bay and developing future pollution regulation and control measures.

Occurrence, risk, and treatment of ciprofloxacin and clarithromycin in drainage

The widespread occurrence of antibiotics in the environment is a global problem, but their occurrence and spatiotemporal distribution, as that of their associated antibiotic-resistant genes and bacteria in Hong Kong estuaries and coast, are poorly understood or documented. Here, the long-term influences of ciprofloxacin (CIP) and clarithromycin (CLR) along the Kai Tak River (KTR) nullah, a man-made channel transporting treated effluents from two wastewater treatment plants, were monitored from December 2019 to April 2021. The results revealed that these antibiotics were widely distributed, exhibiting seasonal variations around median concentrations of 1693.8 ng L−1 for CIP and 632.1 ng L−1 for CLR. The ecological risk assessment indicated that ciprofloxacin and clarithromycin are the predominant ecological risk contributors to aquatic organisms in KTR water. The antibiotic resistance genes (ARGs) of acrB-1, acrA-2, mexF, acrA-1, and mexE persist in the sampled water along with CIP, CLR, and CIP/CLR-resistant bacteria. In addition, a PbO2 thin film electrode of superb stability and electrochemical activity was fabricated by an electrodeposition method and used for the electrochemical oxidation of antibiotic water pollutants. As a result, CIP and CLR were rapidly removed and degraded within fifteen minutes by electron transfer and reactive oxygen species, thus, mitigating ARG contamination in the nullah.

Dissemination of antibiotic resistance genes from the Pearl River Estuary to adjacent coastal areas

The spread of antibiotic resistance genes (ARGs) is a growing concern over the world's various environments. Coastal environments may receive pollutants from land runoffs via estuaries. However, the impact of ARG contamination from estuarine regions to coastal areas is rarely reported. This study used high-throughput quantitative PCR to examine the diversity and abundance of ARGs in Pearl River Estuary (PRE) and adjacent coastal areas. We found that the distribution of ARGs in seawater exhibited the distance-decay phenomenon from the estuary to coastal areas, while the sediment samples did not exhibit an obvious distribution pattern. The estuarine water was found to be the hotspot of ARGs, with 74 ARG species detected and absolute abundance being 5.93 × 105 copies per mL, on average, while less species and lower abundance of ARGs were detected in coastal waters. Ordination analysis showed that estuarine ARG communities were significantly different from coastal ARG communities for water samples. SourceTracker analysis revealed that ARGs from the estuarine environment contributed only a minor fraction of ARG contamination to downstream coastal areas (1.5%–7.4% for water samples, and 0.7–1.8% for sediment samples), indicating the strong dilution effect of seawater. Mantel tests, redundancy analysis and random forest model analysis identified salinity, nutrients, microbial community structure and mobile genetic elements (MGEs) as important factors influencing ARG distribution. Partial least squares-path model revealed that, among all environmental factors, MGEs directly affected the distribution of ARGs, while other factors indirectly contributed by affecting the MGEs assemblage. Our study provides insight into the dissemination of ARGs from the PRE to adjacent coastal areas.

Sulfur: a neglected driver of the increased abundance of antibiotic resistance genes in agricultural reclaimed subsidence land located in coal mines with high phreatic water levels

Due to the shallow burial of groundwater in coal mines with a high phreatic water level, a large area of subsidence lakes is formed after the mine collapses. Agricultural and fishery reclamation activities have been carried out, which introduced antibiotics and exacerbated the contamination of antibiotic resistance genes (ARGs), but this has received limited attention. This study analyzed ARG occurrence in reclaimed mining areas, the key impact factors, and the underlying mechanism. The results show that sulfur is the most critical factor impacting the abundance of ARGs in reclaimed soil, which is due to changes in the microbial community. The species and abundance of ARGs in the reclaimed soil were higher than those in the controlled soil. The relative abundances of most ARGs increased with the depth of reclaimed soil (from 0 to 80 cm). In addition, the microbial structures of the reclaimed and controlled soils were significantly different. Proteobacteria, was the most dominant microbial phylum in the reclaimed soil. This difference is likely related to the high abundance of sulfur metabolism functional genes in the reclaimed soil. Correlation analysis showed that the differences in ARGs and microorganisms in the two soil types were highly correlated with the sulfur content. High levels of sulfur promoted the proliferation of sulfur-metabolizing microbial populations such as Proteobacteria and Gemmatimonadetes in the reclaimed soils. Remarkably, these microbial phyla were the main antibiotic-resistant bacteria in this study, and their proliferation created conditions for the enrichment of ARGs. Overall, this study underscores the risk of the abundance and spread of ARGs driven by high-level sulfur in reclaimed soils and reveals the mechanisms.

Soil Component: A Potential Factor Affecting the Occurrence and Spread of Antibiotic Resistance Genes.

In recent years, antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in soil have become research hotspots in the fields of public health and environmental ecosystems, but the effects of soil types and soil components on the occurrence and spread of ARGs still lack systematic sorting and in-depth research. Firstly, investigational information about ARB and ARGs contamination of soil was described. Then, existing laboratory studies about the influence of the soil component on ARGs were summarized in the following aspects: the influence of soil types on the occurrence of ARGs during natural or human activities and the control of exogenously added soil components on ARGs from the macro perspectives, the effects of soil components on the HGT of ARGs in a pure bacterial system from the micro perspectives. Following that, the similarities in pathways by which soil components affect HGT were identified, and the potential mechanisms were discussed from the perspectives of intracellular responses, plasmid activity, quorum sensing, etc. In the future, related research on multi-component systems, multi-omics methods, and microbial communities should be carried out in order to further our understanding of the occurrence and spread of ARGs in soil.