Potential Hosts Of Antibiotic Resistance Genes Research Articles

Antibiotics and Pesticides Enhancing the Transfer of Resistomes among Soil-Bayberry-Fruit Fly Food Chain in the Orchard Ecosystem.

While substantial amounts of antibiotics and pesticides are applied to maintain orchard yields, their influence on the dissemination and risk of antibiotic resisitome in the orchard food chain remains poorly understood. In this study, we characterized the bacterial and fungal communities and differentiated both antibiotic resistance genes (ARGs) and virulence factor genes (VFGs) in the soil, Chinese bayberry (matured and fallen), and fruit fly gut, collected from five geographic locations. Our results showed that fruit fly guts and soils exhibit a higher abundance of ARGs and VFGs compared with bayberry fruits. We identified 112 shared ARGs and 75 shared VFGs, with aminoglycoside and adherence factor genes being among the most abundant. The co-occurrence network revealed some shared microbes, such as Bacillus and Candida, as potential hosts of ARGs, highlighting the vector risks for both above- and below-ground parts of the orchard food chain. Notably, the elevated levels of antibiotics and pesticide residues in orchard soils increase ARGs, mobile genetic elements (MGEs), and VFGs in the soil-bayberry-fruit fly food chain. Our study highlighted that agricultural management, including the overuse of antibiotics and pesticides, could be the key factor in accumulating resistomes in the orchard food chain.

The variation of resistome, mobilome and pathogen in domestic and industrial wastewater treatment systems

Wastewater treatment plants (WWTPs), including both domestic and industrial facilities, are key contributors to antibiotic resistance genes (ARGs) and human pathogens in the environment. However, the characteristics and dissemination mechanisms of ARGs in domestic (SD) and industrial (SI) wastewater treatment systems remain unclear, leading to uncertainties in risk assessment. Based on metagenomic analysis, we observed significant differences in the compositions of resistome (ARGs and metal resistance genes, MRGs), mobilome (mobile genetic elements, MGEs), and bacterial community between SD and SI. SI exhibited lower diversity of ARGs but higher abundance of MRGs compared to SD. The removal efficiency of resistome was lower in the SI than that in the SD. MGEs emerged as the primary driver of ARG dissemination in the WWTPs, followed by the bacterial community. Environmental conditions (physicochemical parameters, heavy metals, and antibiotics) indirectly influenced the variation of resistome. Significantly, environmental conditions and MGEs highly influenced the composition of resistome in the SI, while bacterial community more associated with resistome in the SD. Additionally, we identified 36 human bacterial pathogens as potential hosts of ARGs, MRGs, and MGEs in wastewater samples. This study provides new insights on the dissemination mechanisms and risk assessment of antimicrobial resistance in the different types of WWTPs.

Understanding the mechanism of microplastic-associated antibiotic resistance genes in aquatic ecosystems: Insights from metagenomic analyses and machine learning

The pervasive presence of microplastics (MPs) in aquatic systems facilitates the transmission of antibiotic resistance genes (ARGs), thereby posing risks to ecosystems and human well-being. However, owing to variations in environmental backgrounds and the limited scope of research subjects, studies on ARGs in MPs lack unified conclusions, particularly regarding whether different types of MPs selectively promote ARG enrichment. Analysing large-scale datasets can better encompass broad spatiotemporal scales and diverse samples, facilitating a more extensive exploration of the complex ecological relationships between MPs and ARGs. The present study integrated existing metagenomic datasets to conduct a comprehensive risk assessment and comparative analysis of resistance groups across various MPs. In addition, we endeavoured to elucidate potential associations between ARGs and bacterial taxa, as well as MP structural features, using machine learning (ML) methods. The findings of our research highlight the pivotal role of MP type in shaping plastispheres, accounting for 9.56 % of the biotic variation (Adonis index) and explaining 18.59 % of the ARG variance. Compared to conventional MPs, biodegradable MPs, such as polyhydroxyalkanoates (PHA) and polylactic acid (PLA), exhibit lower species uniformity and diversity but pose a higher risk of ARG occurrence. These ML approaches effectively forecasted ARG abundance by using the bacterial taxa and molecular structure descriptors (MDs) of MPs (average R2tra = 0.882, R2test = 0.759). Feature analysis showed that MDs associated with lipophilicity, solubility, toxicity, and surface potential significantly influenced the relative abundance of ARGs in the plastispheres. The interpretable multiple linear regression (MLR) model, particularly notable, elucidated a linear relationship between bacterial genera and ARGs, offering promise for identifying potential ARG hosts. This study offers novel insights into ARG dynamics and ecological risks within aquatic plastispheres, highlighting the importance of comprehensive MP monitoring initiatives.

The effect of extracellular polymeric substances on the distribution and transmission of antibiotic resistance genes treating antibiotic wastewater via microbial electrolysis cells

Microbial electrolysis cells (MEC) have emerged as a prominent technology for the treatment of antibiotics-containing wastewater in recent years. However, there remains a dearth of comprehensive exploration regarding the influence of extracellular polymers substances (EPS) on the distribution and transmission of antibiotic resistance genes (ARGs) in MEC. In this study, we quantified the distribution of ARGs in MEC by Fluorescence quantitative polymerase chain reaction and explored with emphasis on impact of EPS component on ARGs transmission at under different concentrations of roxithromycin. Results showed that the absolute abundance of ARGs in the electrode biofilm was 1–2 orders of magnitude higher than that in the anolyte. Specifically, EPS-associated ARGs accounted for 2.31%–11.18% of ARGs in electrode biofilm. The presence of elevated roxithromycin concentration led to electroactive microorganisms (Geobacter and Geothrix) as potential hosts of ARGs. In addition, both protein and polysaccharide content in the electrode biofilm increased with increasing roxithromycin concentration and showed positive correlations with EPS-associated ARGs. Fluorescence quenching experiments further elucidated that tryptophan and tyrosine residues in EPS could bind to ARGs effectively, contributing the hindering the ARGs transmission between hosts. Therefore, increased EPS content within electrode biofilm could reduce the concentration of ARGs present in anolyte while also influencing ARGs distribution throughout MEC. This study provides valuable insights into the distribution of ARGs in MEC systems and the role of EPS in regulating ARGs migration.

The occurrence of banana Fusarium wilt aggravates antibiotic resistance genes dissemination in soil

The spread of antibiotic resistance genes (ARGs) and subsequent soil-borne disease outbreaks are major threats to soil health and sustainable crop production. However, the relationship between occurrences of soil-borne diseases and the transmission of soil ARGs remains unclear. Here, soil ARGs, mobile genetic elements and microbial communities from co-located disease suppressive and conducive banana orchards were deciphered using metagenomics and metatranscriptomics approaches. In total, 23 ARG types, with 399 subtypes, were detected using a metagenomics approach, whereas 23 ARG types, with 452 subtypes, were discovered using a metatranscriptomics method. Furthermore, the metagenomics analysis revealed that the ARG total abundance levels were greater in rhizospheres (0.45 ARGs/16S rRNA on average) compared with bulk (0.32 ARGs/16S rRNA on average) soils. Interestingly, metatranscriptomics revealed that the total ARG abundances were greater in disease-conducive (8.85 ARGs/16S rRNA on average) soils than disease suppressive (1.45 ARGs/16S rRNA on average) soils. Mobile genetic elements showed the same trends as ARGs. Network and binning analyses indicated that Mycobacterium, Streptomyces, and Blastomonas are the main potential hosts of ARGs. Furthermore, Bacillus was significantly and negatively correlated with Fusarium (P < 0.05, r = −0.84) and hosts of ARGs (i.e., Mycobacterium, Streptomyces, and Blastomonas). By comparing metagenomic and metatranscriptomic analyses，this study demonstrated that metatranscriptomics may be more sensitive in indicating ARGs activities in soil. Our findings enable the more accurate assessment of the transmission risk of ARGs. The data provide a new perspective for recognizing soil health, in which soil-borne disease outbreaks appear to be associated with ARG spread, whereas beneficial microbe enrichment may mitigate wilt disease and ARG transmission.

Sewerage surveillance tracking characteristics of human antibiotic resistance genes in sewer system

Sewage surveillance is widely applied to track valid human excretion information and identify public health conditions during corona virus disease 2019 (COVID-19) pandemic. This approach can be applied to monitor the antibiotic resistance level in sewers and to assess the risk of spreading antibiotic resistance in municipal wastewater systems. However, there is still little information about human antibiotic resistance occurrence characteristics in sewer system. This study conducted a field trial for whole year to advance understanding on spatial and temporal occurrence of antibiotic resistance genes (ARGs) in gravity sewerage. The spatial distribution of ARGs along the drainage pipe line (from human settlements to wastewater treatement pant (WWTP)) was insignificant, which may be affected by irregular human emission alongside the pipeline. The correlation between ARGs and antibiotics in sewage was insignificant. The temporal distribution showed that the effect of temperature on ARGs abundance was evident, the ARGs abundance in sewage was generally higher during the cold season. Metagenomic analysis revealed that the detected ARGs were mainly distributed in Proteobacteria (47.51 %) and Antinobacteria (20.11 %). Potential hosts of ARGs in sewage were mainly identified as human gut microorganisms, including human pathogenic bacteria, such as Prevotella, Kocuria, and Propionibacterium, etc. This study provides a new insight into the sewerage surveillance tracking characteristics of human ARGs in sewer system, and suggesting that the sewage-carried ARGs surveillance is a promising method for assessment and management of antibiotic resistance level on population size.

Gut microbiome and antibiotic resistance genes in plateau model animal (Ochotona curzoniae) exhibit a relative stability under cold stress

Antibiotic resistance genes (ARGs) carried by gut pathogens may pose a threat to the host and ecological environment. However, few studies focus on the effects of cold stress on intestinal bacteria and ARGs in plateau animals. Here, we used 16S rRNA gene sequencing and gene chip technique to explore the difference of gut microbes and ARGs in plateau pika under 4 °C and 25 °C. The results showed that tetracycline and aminoglycoside resistance genes were the dominant ARGs in pika intestine. Seven kinds of high-risk ARGs (aadA-01, aadA-02, ermB, floR, mphA-01, mphA-02, tetM-02) existed in pika’s intestine, and cold had no significant effect on the composition and structure of pika’s intestinal ARGs. The dominant phyla in pika intestine were Bacteroidetes and Firmicutes. Cold influenced 0.47 % of pika intestinal bacteria in OTU level, while most other bacteria had no significant change. The diversity and community assembly of intestinal bacteria in pika remained relatively stable under cold conditions, while low temperature decreased gut microbial network complexity. In addition, low temperature led to the enrichment of glycine biosynthesis and metabolism-related pathways. Moreover, the correlation analysis showed that eight opportunistic pathogens (such as Clostridium, Staphylococcus, Streptococcus, etc.) detected in pika intestine might be potential hosts of ARGs.

Impact of Combined Pollution of Ciprofloxacin and Copper on the Diversity of Archaeal Communities and Antibiotic-Resistance Genes.

This study aimed to explore the response of archaeal communities and antibiotic-resistance genes (ARGs) to ciprofloxacin (CIP, 0.05-40 mg/L) and copper (Cu, 3 mg/L) combined pollution during stress- and post-effect periods in an activated sludge system. With the increase in the CIP concentration, the diversity of archaea decreased, but the richness increased under the stress of 10 mg/L CIP. Under stress and post effects, the change in unknown archaeal community structure was more significant than that of the known archaea. The relative abundance of unknown archaea was significantly reduced with the increase in CIP concentration. Meanwhile, there were certain archaea that belonged to abundant and rare taxa with different resistance and recovery characteristics. Among them, Methanosaeta (49.15-83.66%), Methanoculleus (0.11-0.45%), and Nitrososphaera (0.03-0.36%) were the typical resistant archaea to combined pollution. And the resistance of the abundant taxa to combined pollution was significantly higher than that of the rare taxa. Symbiotic and competitive relationships were observed between the known and the unknown archaea. The interactions of abundant known taxa were mainly symbiotic relationships. While the rare unknown taxa were mainly competitive relationships in the post-effect period. Rare archaea showed an important ecological niche under the stress-effect. Some archaea displayed positive correlation with ARGs and played important roles as potential hosts of ARGs during stress- and post-periods. Methanospirillum, Methanosphaerula, Nitrososphaera and some rare unknown archaea also significantly co-occurred with a large number of ARGs. Overall, this study points out the importance of interactions among known and unknown archaeal communities and ARGs in a wastewater treatment system under the stress of antibiotics and heavy metal combined pollution.

Efficient elimination of antibiotic resistome in livestock manure by semi-permeable membrane covered hyperthermophilic composting

Livestock manure is a hotspot for antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs), and an important contributor to antibiotic resistance in non-clinical settings. This study investigated the effectiveness and potential mechanisms of a novel composting technology, semi-permeable membrane covered hyperthermophilic composting (smHTC), in removal of ARGs and MGEs in chicken manure. Results showed that smHTC was more efficient in removal of ARGs and MGEs (92% and 93%) compared to conventional thermophilic composting (cTC) (76% and 92%). The efficient removal in smHTC is attributed to direct or indirect negative effects caused by the high temperature, including reducing the involvement of bio-available heavy metals (HMs) in co-selection processes of antibiotic resistance, decreasing the bacterial abundance and diversity, suppressing the horizontal gene transfer and killing potential ARGs hosts. Overall, smHTC can efficiently remove the resistome in livestock manure, reducing the risk to crops and humans from ARGs residues in compost products.

Parachlorometaxylenol stress caused multidrug-type antibiotic resistance genes proliferation via simultaneously reshaping microbial community and interfering metabolic traits during wastewater treatment process

Despite biological wastewater treatment processes (e.g., sequencing batch reactors (SBR)) being able to reduce the dissemination of antibiotic resistance genes (ARGs), the variation of ARGs under exogenous pollutant stress is an open question. This work investigated the impacts of para-chloro-meta-xylenol (PCMX, typical antibacterial contaminants) on ARGs spread in long-term SBR operation. Although the SBR process inherently decreased ARGs abundance, the presence of PCMX substantially amplified both the prevalence (mainly multidrug) and abundance of total ARGs (1.17-fold of the control). Further analysis demonstrated that PCMX disintegrated sludge structures as well as increased membrane permeability, facilitating the release of mobile genetic elements and subsequent horizontal transfer of ARGs. In addition, PCMX selectively enriched potential ARG hosts, notably Nitrospira and Candidatus Accumulibacter, which predominantly served as multidrug ARG hosts. Concurrently, the self-adaptive functions of ARGs hosts in the PCMX-exposed SBR system were activated via quorum sensing, two-component regulatory system, ATP-binding cassette transporters, and bacterial secretion system. The upregulation of these metabolic pathways also contributed to the dissemination of ARGs.

Improving antibiotic resistance removal from piggery wastewater by involving zero-valent iron within an integrated anoxic-aerobic biofilm reactor

This study introduces zero-valent iron (ZVI) to enhance the removal of antibiotic resistance in piggery wastewater. Two integrated anoxic-aerobic biofilm reactors (IAOBRs) were operated simultaneously for 120 days, with one serving as a control reactor and the other as experimental reactor supplemented with ZVI. The experimental reactor demonstrated superior antibiotic removal efficiencies (89.8 ± 4.5 %), eliminating 99.7 ± 0.7 % of sulfonamides, 91.6 ± 4.5 % of tetracyclines and 81.1 ± 8.4 % of quinolones. The antibiotic resistance bacteria, antibiotic resistance genes (ARGs) and mobile genetic elements removal efficiency reached 0.69–1.74, 2.06 and 2.15 logs, respectively. In comparison to the control reactor, the activated sludge in the experimental reactor also experienced a reduction in total antibiotic concentrations by 57.58 ± 19.99 %. The enhanced performance of the iron-mediated process in antibiotic resistance removal is attributed to the augmentation of enzymatic activity, biodegradation ability, and enrichment of specific microorganisms. The introduction of ZVI also modified the microbial community composition and decreased the potential hosts of ARGs. The proposed iron-mediated process greatly enhances antibiotic resistance removal from wastewater and mitigates antibiotic accumulation in activated sludge, offering new insights into wastewater biological treatment for eliminating antibiotic resistance.

Suppressing Ralstonia solanacearum and Bacterial Antibiotic Resistance Genes in Tomato Rhizosphere Soil through Companion Planting with Basil or Cilantro

The effects of companion planting on soil antibiotic resistance genes (ARGs) and associated microbial composition have remained largely unclear until now. In this study, we assessed the changes in the soil microbiome and ARGs frequencies for tomato growing soils that were companion planted with basil (TB) or cilantro (TC) using a metagenome approach. The abundance of the phytopathogen Ralstonia solanacearum was significantly lower in the TC or TB treatments compared to the tomato monoculture soils (TT). A significant enrichment of Pseudomonas and Aquabacterium and a depletion of Nocardioides and Streptomyces were observed in the TC treatment. Interestingly, both TC and TB companion planting reduced the absolute abundance and the number of subtypes of ARGs. The TC soil showed the lowest numbers of unique ARG subtypes, especially the ARGs resistant to vancomycin and rifamycin, as well as those associated with multidrug resistance. Furthermore, network analysis further revealed that Nocardioides and Streptomyces were potential hosts of ARGs, whereas Flavobacterium negatively correlated with mdtG, suggesting a suppressive effect in reducing ARGs. Together, our results suggest that the companion planting of tomatoes with basil or cilantro can reduce the risk of ARG accumulation, making it a feasible farming management tool to promote soil and plant health in sustainable agriculture.

Oxygen mediated mobilization and co-occurrence of antibiotic resistance in lab-scale bioreactor using metagenomic binning.

Sub-lethal levels of antibiotic stimulate bacteria to generate reactive oxygen species (ROS) that promotes emergence and spread of antibiotic resistance mediated by mobile genetic elements (MGEs). Nevertheless, the influence of dissolved oxygen (DO) levels on mobility of antibiotic resistance genes (ARGs) in response to ROS-induced stress remains elusive. Thus, the study employs metagenomic assembly and binning approaches to decipher mobility potential and co-occurrence frequency of ARGs and MGEs under hyperoxic (5.5-7 mgL- 1), normoxic (2.5-4 mgL- 1), and hypoxic (0.5-1 mgL- 1) conditions in lab-scale bioreactor for 6 months. Among 163 high-quality metagenome-assembled genomes (MAGs) recovered from 13 metagenomes, 42 MAGs harboured multiple ARGs and were assigned to priority pathogen group. Total ARG count increased by 4.3 and 2.5% in hyperoxic and normoxic, but decreased by 0.53% in hypoxic conditions after 150 days. On contrary, MGE count increased by 7.3-1.3% in all the DO levels, with only two ARGs showed positive correlation with MGEs in hypoxic compared to 20 ARGs under hyperoxic conditions. Opportunistic pathogens (Escherichia, Klebsiella, Clostridium, and Proteus) were detected as potential hosts of ARGs wherein co-localisation of critical ARG gene cassette (sul1, dfr1,adeF, and qacC) were identified in class 1 integron/Tn1 family transposons. Thus, enhanced co-occurrence frequency of ARGs with MGEs in pathogens suggested promotion of ARGs mobility under oxidative stress. The study offers valuable insights into ARG dissemination and hosts dynamics that is essential for controlling oxygen-related stress for mitigating MGEs and ARGs in the environment.

Potential of combined reactor and static composting applications for the removal of heavy metals and antibiotic resistance genes from chicken manure

Chicken manure (CM) can pose a serious threat to environmental and human health, and need to be managed properly. The compost can effectively treat CM. However, there is limited research on the heavy metals and antibiotic resistance genes (ARGs) during compost CM. In this study, the combined application of reactor and static composting (RSC) was used to produce organic fertilizer of CM (OCM), and heavy metals, ARGs and bacterial community structure was investigated. The results show that RSC could be used to produce OCM, and OCM meet the National organic fertilizer standard (NY/T525-2021). Compared to the initial CM, DTPA-Cu, DTPA-Zn, DTPA-Pb, DTPA-Cr, DTPA-Ni and DTPA-As in OCM decreased by 40.83%, 23.73%, 34.27%, 38.62%, 16.26%, and 43.35%, respectively. RSC decreased the relative abundance of ARGs in CM by 84.06%, while the relative abundance of sul1 and ermC increased. In addition, the relative abundance and diversity of ARGs were mainly influenced by the bacterial community, with Actinobacteria, Firmicutes, and Proteobacteria becoming the dominant phyla during composting, and probably being the main carriers and dispersers of most of the ARGs. Network analyses confirmed that Gracilibacillus, Lactobacillus, Nocardiopsis, Mesorhizobium and Salinicoccus were the main potential hosts of ARGs, with the main potential hosts of sul1 and ermC being Mesorhizobium and Salinicoccus. The passivation and physicochemical properties of heavy metals contribute to the removal of ARGs, with sul1 and ermC being affected by the toal heavy metals. Application of RSC allows CM to produce mature, safe organic fertilizer after 32 d and reduces the risk of rebound from ARGs, but the issues of sul1 and ermC gene removal cannot be ignored.

Effects of eutrophication on the horizontal transfer of antibiotic resistance genes in microalgal-bacterial symbiotic systems

Overloading of nutrients such as nitrogen causes eutrophication of freshwater bodies. The spread of antibiotic resistance genes (ARGs) poses a threat to ecosystems. However, studies on the enrichment and spread of ARGs from increased nitrogen loading in algal-bacterial symbiotic systems are limited. In this study, the transfer of extracellular kanamycin resistance (KR) genes from large (RP4) small (pEASY-T1) plasmids into the intracellular and extracellular DNA (iDNA, eDNA) of the inter-algal environment of Chlorella pyrenoidosa was investigated, along with the community structure of free-living (FL) and particle-attached (PA) bacteria under different nitrogen source concentrations (0–2.5 g/L KNO3). The results showed that KR gene abundance in the eDNA adsorbed on solid particles (D-eDNA) increased initially and then decreased with increasing nitrogen concentration, while the opposite was true for the rest of the free eDNA (E-eDNA). Medium nitrogen concentrations promoted the transfer of extracellular KR genes into the iDNA attached to algal microorganisms (A-iDNA), eDNA attached to algae (B-eDNA), and the iDNA of free microorganisms (C-iDNA); high nitrogen contributed to the transfer of KR genes into C-iDNA. The highest percentage of KR genes was found in B-eDNA with RP4 plasmid treatment (66.2%) and in C-iDNA with pEASY-T1 plasmid treatment (86.88%). In addition, dissolved oxygen (DO) significantly affected the bacterial PA and FL community compositions. Nephelometric turbidity units (NTU) reflected the abundance of ARGs in algae. Proteobacteria, Cyanobacteria, Bacteroidota, and Actinobacteriota were the main potential hosts of ARGs. These findings provide new insights into the distribution and dispersal of ARGs in the phytoplankton inter-algal environment.

Spatiotemporal Changes of Antibiotic Resistance, Potential Pathogens, and Health Risk in Kindergarten Dust.

The microorganisms present in kindergartens are extremely important for children's health during their three-year preschool education. To assess the risk of outdoor dust in kindergartens, the antibiotic resistome and potential pathogens were investigated in dust samples collected from 59 kindergartens in Xiamen, southeast China in both the winter and summer. Both high-throughput quantitative PCR and metagenome analysis revealed a higher richness and abundance of antibiotic resistance genes (ARGs) in winter (P < 0.05). Besides, the bloom of ARGs and potential pathogens was evident in the urban kindergartens. The co-occurrence patterns among ARGs, mobile genetic elements (MGEs), and potential pathogens suggested some bacterial pathogens were potential hosts of ARGs and MGEs. We found a large number of high-risk ARGs in the dust; the richness and abundance of high-risk ARGs were higher in winter and urban kindergartens compared to in summer and peri-urban kindergartens, respectively. The results of the co-occurrence patterns and high-risk ARGs jointly reveal that urbanization will significantly increase the threat of urban dust to human beings and their risks will be higher in winter. This study unveils the close association between ARGs/mobile ARGs and potential pathogens and emphasizes that we should pay more attention to the health risks induced by their combination.

Exploring the effects of zeolite, biochar, and diatomite as additives for enhancing heavy metals passivation and eliminating antibiotic resistance genes in composts during vermicomposting of dewatered sludge and green waste

Vermicomposting is an effective technology for disposing of municipal sewage sludge and green wastes; however, it can contain heavy metals (HMs) and antibiotic resistance genes (ARGs); thus, the application of the final product to land is risky. In this study, zeolite (ZL), bamboo biochar (BB), and diatomite (DM) were individually mixed with dewatered sludge and green waste at a rate of 5% (w/w) to investigate their effects on earthworm activities, physicochemical characteristics of vermicompost, HMs and ARGs patterns, and microbial community structure during vermicomposting. The results showed that ZL, BB, and DM stimulated the growth and fecundity of earthworms, accompanied by higher degradation of organic matter, nutritional value, humification level, and maturity of final products. The distribution rate of OXI-Zn and RES-Pb in vermicomposts could be increased by 3.48%−11.53% and 8.64%−17.53%, respectively, under all additives addition treatments in comparison to the control treatment. Moreover, the addition of ZL, BB, and DM significantly enhanced the reduction rate of intI-1 (2.45%−20.86%), sul1 (8.16%−26.46%), sul2 (18.88%−29.55%), ermB (30.25%−40.08%), ermC (19.25%−28.53%), gryA (22.99%−30.04%), parC (18.75%−20.46%), qnrS (11.58%−28.96%) and tetC (18.99%−21.57%) genes in vermicomposts, as compared to control without additives. ZL, BB, and DM addition optimized the bacterial community by decreasing the abundances of the potential ARGs hosts, such as Steroidobacter and Acidibacter, enhancing important organic-decomposing bacteria, such as cellulomonas and Chryseolinea. This study newly suggests that ZL, BB, and DM addition is beneficial for the passivation of Zn and Pb and decreases the dissemination risk of ARGs in vermicomposting dewatered sludge and green waste.

Distribution characteristics of antibiotic resistance genes and microbial diversity in the inshore aquaculture area of Wenchang, Hainan, China

The rapid development of marine aquaculture has led to the increased use and release of antibiotics into the marine environment, consequently contributing to the emergence of antibiotic resistance. Information on antibiotic resistance in nearshore marine aquaculture areas remains limited, and research on the microbial composition and potential hosts of antibiotic resistance genes (ARGs) in marine aquaculture areas is scarce. This study used SmartChip real-time fluorescent quantitative PCR and qPCR to quantitatively analyze 44 ARGs and 10 mobile genetic elements (MGEs) genes in 12 sampling points in the nearshore aquaculture area of Wenchang. High-throughput sequencing of 16S rRNA was used to study microbial diversity in the study area, to clarify the correlation between ARGs, MGEs, and microbial diversity, and to determine the possible sources and potential hosts of ARGs. The results showed that a total of 37 ARGs and 8 MGEs were detected in the study area. The detection rate of 9 ARGs (aac(6′)-Ib(aka aacA4)-02, catA1, cmlA, cfr, sul1, sul2, sulA/folP-01, tetC, tetX) was 100 %. The absolute abundance of ARGs in the 12 sampling points ranged from 2.75 × 107 to 3.79 × 1010 copies·L−1, and the absolute abundance of MGEs was 1.30 × 105 to 2.54 × 107 copies·L−1, which was relatively high compared to other research areas. ARGs and MGEs were significantly correlated, indicating that MGEs play an important role as a mediator in the spread of ARGs. At the phylum level, Proteobacteria and Cyanobacteria were the dominant bacteria in the study area, with HIMB11 and unidentifiedChloroplast being the dominant levels, respectively. Network analysis of ARGs and microorganisms (genus level) revealed that Cognatishimia, Thalassobius, Aestuariicoccus, Thalassotalea, and Vibrio were significantly correlated with multiple ARGs and were the main potential hosts of ARGs in the nearshore waters of Wenchang.

Microplastics shape microbial interactions and affect the dissemination of antibiotic resistance genes in different full-scale wastewater treatment plants

Wastewater treatment plants (WWTPs) pose a potential threat to the environment because of the accumulation of antibiotic resistance genes (ARGs) and microplastics (MPs). However, the interactions between ARGs and MPs, which have both indirect and direct effects on ARG dissemination in WWTPs, remain unclear. In this study, spatiotemporal variations in different types of MPs, ten ARGs (sul1, sul2, tetA, tetO, tetM, tetX, tetW, qnrS, ermB, and ermC), class 1 integron integrase (intI1) and transposon Tn916/1545 in three typical WWTPs were characterized. Sul1, tetO, and sul2 were the predominant ARGs in the targeted WWTPs, whereas the intI1 and transposon Tn916/1545 were positively correlated with most of the targeted ARGs. Saccharimonadales (4.15 %), Trichococcus (2.60 %), Nitrospira (1.96 %), Candidatus amarolinea (1.79 %), and SC-I-84 (belonging to phylum Proteobacteria) (1.78 %) were the dominant genera. Network and redundancy analyses showed that Trichococcus, Faecalibacterium, Arcobacter, and Prevotella copri were potential hosts of ARGs, whereas Candidatus campbellbacteria and Candidatus kaiserbacteria were negatively correlated with ARGs. The potential hosts of ARGs had a strong positive correlation with polyethylene terephthalate, silicone resin, and fluor rubber and a negative correlation with polyurethane. Candidatus campbellbacteria and Candidatus kaiserbacteria were positively correlated with polyurethane, whereas potential hosts of ARGs were positively correlated with polypropylene and fluor rubber. Structural equation modeling highlighted that intI1, transposon Tn916/1545 and microbial communities, particularly microbial diversity, dominated the dissemination of ARGs, whereas MPs had a significant positive correlation with microbial abundance. Our study deepens the understanding of the relationships between ARGs and MPs in WWTPs, which will be helpful in designing strategies for inhibiting ARG hosts in WWTPs.

Metagenomic analysis of antibiotic-resistance genes and viruses released from glaciers into downstream habitats

Glaciers serve as effective reservoirs of antibiotic resistance genes (ARGs) and viruses for millions of years. Climate change and anthropogenic activity have accelerated the melting of glaciers, but the patterns of release of ARGs and viruses from melting glaciers into downstream habitats remain unknown. We analyzed 171 metagenomic samples from glaciers and their downstream habitats and found that the abundance and diversity of ARGs were higher in glaciers (polar and plateau glaciers) than downstream habitats (Arctic Ocean, Qinghai Lake, and Yangtze River Basin), with the diversity of viruses having the opposite pattern. Proteobacteria and Actinobacteria were the main potential hosts of ARGs and viruses, and the richness of ARGs carried by the hosts was positively correlated with viral abundance, suggesting that the transmission of viruses in the hosts could disseminate ARGs. Source tracking indicated that >18 % of the ARGs and >25 % of the viruses detected in downstream habitats originated from glaciers, demonstrating that glaciers could be one of the potential sources of ARGs and viruses in downstream habitats. Increased solar radiation and emission of carbon dioxide mainly influenced the release of the ARGs and viruses from glaciers into downstream habitats. This study provides a systematic insight demonstrating the release of ARGs and viruses from the melting glaciers, potentially increasing ecological pressure.