Hosts Of Antibiotic Resistance Genes Research Articles

Antibiotic resistome and associated bacterial communities in agricultural soil following the amendments of swine manure-derived fermentation bed waste.

The practice of utilizing animal manures on land is widespread in agriculture, but it has raised concerns about the possible spread of antibiotic resistance genes (ARGs) and thepotential risk it poses to public health through food production. Fermentation bed culture is an effective circular agricultural practice commonly utilized in pig farming that minimizes the environmental impact of livestock farming. However, this method generates a significant amount of fermentation bed waste (FBW), which can be turned into organic fertilizer for land application. The objective of this research was to examine the impacts of amending agricultural soil samples with swine manure-derived FBW on microbial communities, mobile genetic elements (MGEs), and ARG profiles over different periods. The study findings indicated that the amendment of swine manure-derived FBW significantly increased the diversity and abundance of ARGs and MGEs during the early stages of amendment, but this effect diminished over time, and after 12months of FBW amendments, the levels returned to those comparable to control samples. The shift in the bacterial communities played a significant role in shaping the patterns of ARGs. Actinobacteriota, Proteobacteria, and Bacteroidetes were identified as the primary potential hosts of ARGs through metagenomic binning analysis. Furthermore, thepH of soil samples was identified as the most important property in driving the composition of the bacterial community and soil resistome. These findings provided valuable insights into the temporal patterns and dissemination risks of ARGs in FBW-amended agriculture soil, which could contribute to the development of effective strategies to manage the dissemination risks of FBW-derived ARGs.

Wastewater treatment plant effluents exert different impacts on antibiotic resistome in water and sediment of the receiving river: Metagenomic analysis and risk assessment

Wastewater treatment plants (WWTPs) are considered as hotspots for the spread of antibiotic resistome into the environment. However, the differential contributions of WWTPs to the antibiotic resistome in the receiving river water and sediment are poorly understood. Here, based on metagenomic analysis, we found that the WWTP effluents significantly elevated the diversities and abundances of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in the receiving river water from the Qinghai-Tibet Plateau, but showed less interference with the antibiotic resistome in sediment. Estimated by SourceTracker, WWTPs contributed 60.691.8% of ARGs in downstream river water, much higher than those for sediment (7.7568.0%). A holistic comparison of ARG risks based on analysis of ARG combination, mobility risk, ARG hosts and ARG-carrying pathogens further revealed the great impacts of WWTP effluents on downstream river water rather than sediment. Among various MGEs, tnpA exhibited the greatest potential for the dissemination of ARGs, and displayed highest co-occurrence frequency with multiple ARGs. P. aeruginosa, E. cloacae, and E. coli were identified as the critical-priority pathogens of ARG hosts. This study demonstrated the much greater impacts of WWTP effluents on the downstream water compared with sediment, which is significant for developing effective strategies to mitigate ARG risks.

Size-dependent promotion of micro(nano)plastics on the horizontal gene transfer of antibiotic resistance genes in constructed wetlands

Constructed wetlands (CWs) have been identified as significant sources of micro(nano)plastics (MPs/NPs) and antibiotic resistance genes (ARGs) in aquatic environments. However, little is known about the impact of MPs/NPs exposure on horizontal gene transfer (HGT) of ARGs and shaping the corresponding ARG hosts’ community. Herein, the contribution of polystyrene (PS) particles (control, 4 mm, 100 μm, and 100 nm) to ARG transfer was investigated by adding an engineered fluorescent Escherichia coli harboring RP4 plasmid-encoded ARGs into CWs. It was found MPs/NPs significantly promoted ARG transfer in a size-dependent manner in each CW medium (p < 0.05). The 100 μm-sized PS exhibited the most significant promotion of ARG transfer (p < 0.05), whereas 100 nm-sized PS induced limited promotion due to its inhibitory activity on microbes. The altered RP4-carrying bacterial communities suggested that MPs/NPs, especially 100 µm-PS, could recruit pathogenic and nitrifying bacteria to acquire ARGs. The increased sharing of RP4-carrying core bacteria in CW medium further suggested that ARGs can spread into CW microbiome using MPs/NPs as carriers. Overall, our results highlight the high risks of ARG dissemination induced by MPs/NPs exposure and emphasize the need for better control of plastic disposal to prevent the potential health threats.

Biofilm electrode reactor coupled manganese ore substrate up-flow microbial fuel cell-constructed wetland system: High removal efficiencies of antibiotic, zinc (II), and the corresponding antibiotic resistance genes

A coupled system comprised of a biofilm electrode reactor (BER) and a manganese ore substrate microbial fuel cell-constructed wetland (MFC-CW) system was used to remove co-exposed antibiotic and Zn (II), as well as simultaneously reduce copies of antibiotic resistance genes (ARGs) in the current study. In this system, BER primarily reduced the concentrations of antibiotics and Zn (II), and the effluent was used as the input to the MFC-CW, thereby providing electricity to BER. Co-exposure to a high concentration of Zn (II) decreased the relative abundances (RAs) of ARGs in the BER effluent, whereas the remaining sub-lethal concentration of Zn (II) increased the RAs of ARGs in the MFC-CW effluent. Even though the absolute copies of ARGs in the effluents increased during co-exposure, the total number of target ARG copies in the effluent of MFC-CW was significantly lower than that of BER. Moreover, BER pre-treatment eliminated most of Zn (II), which improved the electrical power generation characteristic of the MFC-CW unit. Correspondingly, the bacterial community and the ARGs hosts were analyzed to demonstrate the mechanism. In conclusion, the coupled system demonstrates significant potential to reduce antibiotics, Zn (II) and environmental risks posed by ARGs.

Antibiotic resistance gene profiles and evolutions in composting regulated by reactive oxygen species generated via nano ZVI loaded on biochar

In this study, nano zero-valent iron loaded on biochar (BC-nZVI) was analyzed for its effects on antibiotic resistance genes (ARGs) in composting. The results showed that BC-nZVI increased reactive oxygen species (ROS) production, and the peak values of H2O2 and OH were 22.95 % and 55.30 % higher than those of the control group, respectively. After 65 days, the relative abundances of representative ARGs decreased by 56.12 % in the nZVI group (with BC-nZVI added). An analysis of bacterial communities and networks revealed that Actinobacteria, Proteobacteria, and Firmicutes were the main hosts for ARGs, and BC-nZVI weakened the link between ARGs and host bacteria. Distance-based redundancy analysis showed that BC-nZVI altered the microbial community structure through environmental factors and that most ARGs were negatively correlated with ROS, suggesting that ROS significantly affected the relative abundance of ARGs. According to these results, BC-nZVI showed potential for decreasing the relative abundance of ARGs in composting.

Biodegradation of soil agrochemical contamination mitigates the direct horizontal transfer risk of antibiotic resistance genes to crops

Microorganisms can drive a substrate-specific biodegradation process to mitigate soil contamination resulting from extensive agrochemical usage. However, microorganisms with high metabolic efficiency are capable of adapting to the co-occurrence of non-substrate contaminants in the soil (particularly antibiotics). Therefore, the utilization of active microorganisms for biodegradation raises concerns regarding the potential risk of antibiotic resistance development. Here, the horizontal transfer risk of antibiotic-resistance genes (ARGs) in the soil-plant biota was assessed during biodegradation by the newly isolated Proteus terrae ZQ02 (which shortened the half-life of fungicide chlorothalonil from 9.24 d to 2.35 d when exposed to tetracycline). Based on metagenomic analyses, the distribution of ARGs and mobile genetic elements (MGEs) was profiled. The ARGs shared with ∼118 core genes and mostly accumulated in the rhizosphere and maize roots. After ZQ02 was inoculated, the core genes of ARGs reduced significantly in roots. In addition, the Pseudomonas and Proteus genera were identified as the dominant microbial hosts of ARGs and MGEs after ZQ02 adoption. The richness of major ARG hosts increased in soil but barely changed in the roots, which contributed to the mitigation of hosts-mediated ARGs transfer from soil to maize. Finally, the risk of ARGs has been assessed. Compared with the regular planting system, the number of risky ARGs declined from 220 (occupied 4.77 % of the total ARGs) to 143 (occupied 2.67 %) after biodegradation. Among these, 23 out of 25 high-risk genes were aggregated in the soil whereas only 2 genes were identified in roots, which further verified the low antibiotic resistance risk for crop after biodegradation. In a nutshell, this work highlights the critical advantage of ZQ02-based biodegradation that alleviating the ARGs transfer risks from soil to crop, which offers deeper insights into the versatility and feasibility of bioremediation techniques in sustainable agriculture.

Antibiotic resistance genes in constructed wetlands: Driving indicators and risk assessment

Constructed wetlands (CWs) were responsible for the in-depth purification of wastewater, providing an ideal environment for the transport, acquisition, and dissemination of antibiotic resistance genes (ARGs). A better understanding of influencing factors and risks of ARGs in CWs was deemed indispensable. In this research, the abundance of ARGs and mobile genetic elements (MGEs) was determined to be higher in summer and spring, ranging from 53.7 to 8.51 × 106 and 30.9–6.02 × 106 copies/mL, respectively. Seasonal variation significantly influenced the abundance of ARGs and MGEs, as well as the co-occurrence patterns among ARGs, MGEs and bacteria. However, the environmental gradients, from the influent (CW01) to the effluent (CW10), did not impose significant effects on the abundance of ARGs and MGEs. Furthermore, the ratios of pathogenic bacteria to ARG hosts and ARG risks index decreased by 50.4% and 88.54% along with the environmental gradients, indicating that CWs could act as barriers to the transfer of ARGs. Partial least squares-path modeling (PLSPM) revealed that temperature was the main driving factor of ARGs, followed by MGEs, stable and differential bacteria. This finding effectively and innovatively explored the driving indicators for the variations and risks of ARGs caused by spatial-temporal variations, providing new insights into the evaluation and control of ARGs in CWs.

Chlorine disinfection modifies the microbiome, resistome and mobilome of hospital wastewater – A nanopore long-read metagenomic approach

The aim of the present study was to analyze changes in the microbiome, resistome, and mobilome of hospital wastewater (HWW) induced by disinfection with chlorine compounds. Changes in bacterial communities and specific antibiotic resistance genes (ARGs) in HWW were determined with the use of a nanopore long-read metagenomic approach. The main hosts of ARGs in HWW were identified, and the mobility of resistance mechanisms was analyzed. Special attention was paid to the prevalence of critical-priority pathogens in the HWW microbiome, which pose the greatest threat to human health. The results of this study indicate that chlorine disinfection of HWW can induce significant changes in the structure of the total bacterial population and antibiotic resistant bacteria (ARB) communities, and that it can modify the resistome and mobilome of HWW. Disinfection favored the selection of ARGs, decreased their prevalence in HWW, while increasing their diversity. The mobility of the HWW resistome increased after disinfection. Disinfection led to the emergence of new drug resistance mechanisms in previously sensitive bacterial taxa. In conclusion, this study demonstrated that HWW disinfected with low (sublethal) concentrations of free chlorine significantly contributes to the mobility and transfer of drug resistance mechanisms (including critical mechanisms) between bacteria (including pathogens).

Pig manure-derived fulvic acid more strongly drives the fate of arsenic and antibiotic resistance genes in paddy soil

Antibiotic resistance genes (ARGs) can threaten the clean production of rice owing to continuous selective pressure in heavy metal–antibiotic co-contaminated paddy soils. As an important soil carbon reservoir, the role of humic substances from different types of manure in the regulation of soil ARGs remains unclear. In this study, fulvic acid (FA) and humic acid (HA) were extracted from pig manure (PM), cow dung (CD), and chicken manure (CM). The influence of their characteristics and doses on the fate of ARGs was investigated in arsenic (As)–antibiotic co-contaminated paddy soils. The release of As and degradation of antibiotics were promoted in 1% PM-FA treatment, with increases of 4.8%–5.6% and 8.3%–8.8% compared with CM-FA and CD-FA treatments, respectively. The coexistence of FA/HA, Fe, As, and antibiotics in soil pore water affected the environmental behavior of ARGs, with FA showing a more positive effect. Species including Bacillus, Geobacter, Desulfitobacterium, and Christensenellaceae_R-7_group were considered potential hosts of ARGs, and their resistance to co-contamination increased after the addition of FA. Membrane transport is a potential strategy for host bacteria of ARGs to cope with As–antibiotic complex pressure. These results demonstrate the coupling mechanisms of As, antibiotics, and ARGs regulated by different humic substances in co-contaminated paddy soils, which could support the clean production of rice in agricultural practice.

Dynamics of antibiotic resistance genes and bacterial community during pig manure, kitchen waste, and sewage sludge composting

Organic solid wastes (OSWs) are important reservoirs for antibiotic resistance genes (ARGs). Aerobic composting transforms OSWs into fertilizers. In this study, we investigated ARGs dynamics and their driving mechanisms in three OSW composts: pig manure (PM), kitchen waste (KC), and sewage sludge (SG). The dominant ARGs were different in each OSW, namely tetracycline, aminoglycoside, and macrolide resistance (PM); tetracyclines and aminoglycosides (KC); and sulfonamides (SG). ARGs abundance decreased in PM (71%) but increased in KC (5.9-fold) and SG (1.3-fold). Interestingly, the ARGs abundance was generally similar in all final composts, which was contributed to the similar bacterial community in final composts. In particular, sulfonamide and β-lactam resistant genes removed (100%) in PM, while sulfonamide in KC (38-fold) and tetracycline in SG (5-fold) increased the most. Additionally, ARGs abundance rebounded during the maturation period in all treatments. Firmicutes, Proteobacteria, and Actinobacteria were the main ARGs hosts. Several persistent and high-risk genes included tetW, aadA, aadE, tetX, strB, tetA, mefA, intl1, and intl2. The structural equation models showed ARGs removal was mainly affected by physicochemical parameters and bacterial communities in PM, the ARGs enrichment in KC composting correlated with increased mobile genetic elements (MGEs). In general, thermophilic aerobic composting can inhibit the vertical gene transfer (VGT) of pig manure and horizontal gene transfer (HGT) of sludge, but it increases the HGT of kitchen waste, resulting in a dramatic increase of ARGs in KC compost. More attention should be paid to the ARGs risk of kitchen waste composting.

Seasonality Determines the Variations of Biofilm Microbiome and Antibiotic Resistome in a Pilot-Scale Chlorinated Drinking Water Distribution System Deciphered by Metagenome Assembly.

Understanding the biofilm microbiome and antibiotic resistome evolution in drinking water distribution systems (DWDSs) is crucial to ensure the safety of drinking water. We explored the 10 month evolution of the microbial community, antibiotic resistance genes (ARGs), mobile gene elements (MGEs) co-existing with ARGs and pathogenic ARG hosts, and the ARG driving factors in DWDS biofilms using metagenomics assembly. Sampling season was critical in determining the microbial community and antibiotic resistome shift. Pseudomonas was the primary biofilm colonizer, and biofilms diversified more as the formation time increased. Most genera tended to cooperate to adapt to an oligotrophic environment with disinfectant stress. Biofilm microbial community and antibiotic resistome assembly were mainly determined by stochastic processes and changed with season. Metagenome assembly provided the occurrence and fates of MGEs co-existing with ARGs and ARG hosts in DWDS biofilms. The abundance of ARG- and MGE-carrying pathogen Stenotrophomonas maltophilia was high in summer. It primarily harbored the aph(3)-IIb, multidrug transporter, smeD, and metallo-beta-lactamase ARGs, which were transferred via recombination. The microbial community was the most crucial factor driving the antibiotic resistance shift. We provide novel insights about the evolution of pathogens and ARGs and their correlations in DWDS biofilms to ensure the safety of drinking water.

Artificial Sweetener Enhances the Spread of Antibiotic Resistance Genes During Anaerobic Digestion.

Artificial sweeteners have been frequently detected in the feedstocks of anaerobic digestion. As these sweeteners can lead to the shift of anaerobic microbiota in the gut similar to that caused by antibiotics, we hypothesize that they may have an antibiotic-like impact on antibiotic resistance genes (ARGs) in anaerobic digestion. However, current understanding on this topic is scarce. This investigation aimed to examine the potential impact of acesulfame, a typical artificial sweetener, on ARGs in anaerobic digestion by using metagenomics sequencing and qPCR. It was found that acesulfame increased the number of detected ARG classes and the abundance of ARGs during anaerobic digestion. The abundance of typical mobile genetic elements (MGEs) and the number of potential hosts of ARGs also increased under acesulfame exposure, suggesting the enhanced potential of horizontal gene transfer of ARGs, which was further confirmed by the correlation analysis between absolute abundances of the targeted ARGs and MGEs. The increased horizontal dissemination of ARGs may be associated with the SOS response induced by the increased ROS production, and the increased cellular membrane permeability. These findings indicate that artificial sweeteners may accelerate ARG spread through digestate disposal, thus corresponding strategies should be considered to prevent potential risks in practice.

Insights into antibiotic resistance gene abundances and regulatory mechanisms induced by ionic liquids during composting

This study investigated the regulatory mechanism of the evolution of antibiotic resistance genes (ARGs) during the composting process with sawdust and cow manure as raw materials using ionic liquids (ILs) pretreatment. The results showed that genes of MLS, chloramphenicol, tetracycline, beta - lactam as composting gradually decreased. From day0 to day3, MLS in control group (CK) and experimental group (T) decreased by 25.62% and 26.66%, respectively. Tetracycline decreased by 7.21% in CK and by 7.86% in T. Chloramphenicol decreased by 2.85% in CK and 3.34% in T. Beta-lactam decreased by 1.95% in Ck and by 3.69% in T. Mechanism studies have shown that ILs can effectively decompose extracellular polymeric substances (EPS) and enhance lactose dehydrogenase (LDH) release, resulting in ARGs release and elimination. Meanwhile, ILs pretreatment can inhibit growth of some ARGs hosts, especially Firmicutes, resulting in decreased ARGs. Moreover, metabolic pathways and related genes take part in ARGs transmission were down regulated, leading to decreased ARGs.

Insight into the responses of antibiotic resistance genes in microplastic biofilms to zinc oxide nanoparticles and zinc ions pressures in landfill leachate

Microplastic (MP) biofilms are hotspots of antibiotic resistance genes (ARGs) in landfill environment. MP biofilms in landfill leachate coexist with heavy metals and metallic nanoparticles (NPs) that considered to be the selective agents of ARGs. However, the effects of these selective pressures on ARGs in MP biofilms and their differences in MP-surrounding leachate have not been well understood. Herein, the changes of ARG abundances in MP biofilms and corresponding leachate under zinc oxide (ZnO) NPs and zinc ion (Zn2+) pressures were comparatively analyzed. The presence of ZnO NPs and Zn2+ promoted the enrichment of ARGs in MP biofilms, and the enrichment was more pronounced in ZnO NPs groups. ZnO NPs and especially Zn2+ mainly decreased the abundances of ARGs in leachate. The increase of integron abundances and reactive oxygen species production in MP biofilms implied the enhanced potential for horizontal transfer of ARGs under ZnO NPs and Zn2+ pressures. Meanwhile, the co-occurrence pattern between ARGs and bacterial genera in MP biofilms with more diverse potential ARG hosts was more complex than in leachate, and the enrichment of ARG-hosting bacteria in MP biofilms under ZnO NPs and Zn2+ pressures supported the enrichment of ARGs.

Insights into antibiotic resistance-related changes in microbial communities, resistome and mobilome in paddy irrigated with reclaimed wastewater

Reclaimed wastewater (reclaimed wastewater, RWW) from municipal wastewater treatment plants for paddy irrigation is a well-established practice to alleviate water scarcity. However, the reuse may result in the persistent exposure of the paddy to residual antibiotics in RWW. Continuous presence of even low-level antibiotics can exert selective pressure on microbiota, resulting in the proliferation and dissemination of antibiotic resistance genes (ARGs) in paddy. In this study, metagenomic analysis was applied to firstly deciphered the effects of residual antibiotics on microbiome and resistome in constructed mesocosm-scale paddy soils. The diversity and abundance of ARG have remarkably risen with the increasing antibiotic concentration in RWW. Network analysis revealed that 28 genera belonging to six phyla were considered as the potential ARG hosts, and their abundances were enhanced with increasing antibiotic concentrations. A partial least-squares path model indicated that the microbial community was the principal direct driver of the ARG abundance and the resistome alteration in paddy soil under long-term RWW irrigation. Microbes may acquire ARGs via horizontal gene transfer. IntI1 could play an essential role in the propagation and spread of ARGs. Functional analysis suggested that enhanced SOS response and T4SSs (Type IV secretion systems) modules could stimulate horizontal transfer potential and promote the ARG abundance. The obtained results provide a scientific decision for assessing the ecological risk of RWW application.

Methionine influences the profile of intestinal antibiotic resistome through inhibiting the growth of Escherichia coli

Antibiotic resistance genes (ARGs) are a new type of environmental pollutant. However, studies have mainly focused on the distribution characteristics of ARGs in the livestock environment, lacking of studies on the composition of ARGs in the intestinal tract of animals and the effect of nutrients on intestinal ARGs and microbial communities. Reducing antimicrobial resistance and maintaining optimal animal health and performance are urgently needed. Methionine is an essential amino acid which plays a critical role in the growth and reproductive performance of animals. In this study, feeding experiment, in vitro fermentation and bacterial culture experiment were performed to explore the influence of methionine on the intestinal resistome of sows. We found that dietary 0.2 % methionine supplementation decreased the total abundance of intestinal ARGs, which was further confirmed by in vitro fecal microbial fermentation of sows. Metagenome binning analysis identified that Escherichia coli was the major ARG host, which carried 60–113 ARGs and 134–286 virulence factors, indicating that Escherichia coli in the pig intestine is not only a core ARG host, but also an important pathogen. In addition, we found that methionine supplementation inhibited the growth of Escherichia coli, indicating that dietary methionine may reduce the resistome risk in sow intestine by inhibiting core ARG hosts such as Escherichia coli. These findings reveal that dietary methionine application plays a critical role in intestinal antibiotic resistance, providing a new idea for preventing and controlling environmental pollution by antibiotic-resistant microbes.

Unraveling antibiotic resistomes associated with bacterial and viral communities in intertidal mudflat aquaculture area

The extensive use of antibiotics in intertidal mudflat aquaculture area has substantially increased the dissemination risk of antibiotic resistance genes (ARGs). As hosts of ARGs, bacteria and virus exert vital effects on ARG dissemination. However, the insights for the interrelationships among ARGs, bacteria, and virus have not been thoroughly explored in intertidal mudflat. Therefore, this study attempts to unravel the occurrence, dissemination, evolution, and driving mechanisms of ARGs associated with bacterial and viral communities using metagenomic sequencing in a typical intertidal mudflat. Abundant and diverse ARGs (22 types and 437 subtypes) were identified and those of ARGs were higher in spring than in autumn. It is worthy noted that virus occupied a more essential position than bacteria for ARGs dissemination through network analysis. Meanwhile, nitrogen exerted indirect effect on ARG profiles by shaping viral and bacterial diversity. According to the results of neutral and null models, deterministic processes dominated the ARG community assembly by controlling sediment nitrogen and antibiotics. Homogeneous and variable selection dominated phylogenetic turnover of ARG community, contributing 46.15% and 45.90% of the total processes, respectively. This study can hence theoretically support for the ARG pollution control and management in intertidal mudflat aquaculture area.

Enhanced removal of antibiotic and antibiotic resistance genes by coupling biofilm electrode reactor and manganese ore substrate up-flow microbial fuel cell constructed wetland system

Manganese ore substrate up-flow microbial fuel cell constructed wetland (UCW-MFC(Mn)) as an innovative wastewater treatment technology for purifying antibiotics and electricity generation with few antibiotic resistance genes (ARGs) generation has attracted attention. However, antibiotic purifying effects should be further enhanced. In this study, a biofilm electrode reactor (BER) that needs direct current driving was powered by a Mn ore anode (UCW-MFC(Mn)) to form a coupled system without requiring direct-current source. Removal efficiencies of sulfadiazine (SDZ), ciprofloxacin (CIP) and the corresponding ARGs in the coupled system were compared with composite (BER was powered by direct-current source) and anaerobic systems (both of BER and UCW-MFC were in open circuit mode). The result showed that higher antibiotic removal efficiency (94% for SDZ and 99.1% for CIP) in the coupled system was achieved than the anaerobic system (88.5% for SDZ and 98.2% for CIP). Moreover, electrical stimulation reduced antibiotic selective pressure and horizontal gene transfer potential in BER, and UCW-MFC further reduced ARG abundances by strengthening the electro-adsorption of ARG hosts determined by Network analysis. Bacterial community diversity continuously decreased in BER while it increased in UCW-MFC, indicating that BER mitigated the toxicity of antibiotic. Degree of modularity, some functional bacteria (antibiotic degrading bacteria, fermentative bacteria and EAB), and P450 enzyme related to antibiotic and xenobiotics biodegradation genes were enriched in electric field existing UCW-MFC, accounting for the higher degradation efficiency. In conclusion, this study provided an effective strategy for removing antibiotics and ARGs in wastewater by operating a BER-UCW-MFC coupled system.

Response of heavy-metal and antibiotic resistance genes and their related microbe in rice paddy irrigated with treated municipal wastewaters

Paddy irrigation with secondary effluents from municipal wastewater treatment plants (MWTPs) is a well-established practice to alleviate water scarcity. However, the reuse might lead to more complicated contamination caused by interactions between residual antibiotics in effluents and heavy metals in paddy soil. To date, no information is available for the potential effects of dual stress of heavy metals and antibiotics on heavy-metal resistance genes (MRGs) and antibiotic resistance genes (ARGs). Here, this study investigated the response of heavy metal and antibiotic resistance genes, and related microorganisms to the dual threat of antibiotics and heavy metals under the long-term MWTP effluent irrigation for rice paddy using metagenome. The results showed that there was not a negative effect on rice consumption if MWTP effluent was used to irrigate rice for a long time. The concentration of antibiotics could reshape the ARGs and MRG profiles in rice paddy soil. The findings revealed the co-occurrence of ARGs and MRGs in rice paddy soils, thus highlighting the need for simultaneous elimination of antibiotics and heavy metals to effectively reduce ARGs and MRGs. Acn and sul1 genes encoding Iron and sulfonamides resistance mechanisms are the most abundant MRG and ARG, respectively. Network analysis revealed the possibility that IntI1 plays a role in the co-transmission of MRG and ARG to host microbes, and that Proteobacteria are the most dominant hosts for MRG, ARG, and integrons. The presence of antibiotics in irrigated MWTP effluents has been found to stimulate the proliferation of heavy metal and antibiotic resistances by altering soil microbial communities. This study will enhance our comprehension of the co-selection between ARGs and MRGs, as well as reveal the concealed environmental impacts of combined pollution. The obtained results have important implications for food safety and human health in rice.

Antibiotic resistome associated with influencing factors in industrial-scale organic waste aerobic composting plants

This study investigated the fate of antibiotic resistance genes (ARGs) and bacterial evolution in six industrial-scale organic wastes aerobic composting plants and identified key factors driving ARGs dynamics. A total of 226 ARGs and 46 mobile genetic elements (MGEs), mainly resistant to aminoglycoside and MLSB, were detected by high-throughput qPCR. Briefly, aerobic composting showed good performance in reducing the diversity and abundance of ARGs, where the total absolute abundance was reduced by 88.34%–97.08% except for cattle manures. Rapid composting may lead to a rebound of ARGs due to long-term storage compared to traditional composting. Hub ARGs and bacterial genera were screened out by co-occurrence patterns. As the dominant phyla in composting, the main potential hosts of ARGs were Firmicutes, Bacteroidota and Proteobacteria. Structural equation model indicated that MGEs and heavy metals were key factors affecting ARGs dynamics. In addition, nutrients and bacterial α-diversity can indirectly influence ARGs by affecting MGEs.