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(Nano)microplastics promote the propagation of antibiotic resistance genes in landfill leachate
Abstract
Municipal landfill leachate is a huge reservoir of (nano)microplastics (N/MPs) and antibiotic resistance genes (ARGs). N/MPs have a proven ability to affect the growth of bacteria and composition of bacterial communities, which may further influence the spread of ARGs in the environment. To extrapolate the interactions between these two emerging contaminants, we investigated the variations of the ARG levels in leachate with exposures to different sizes of N/MPs. The results showed that ARGs were enriched in the N/MPs-exposed groups, especially in the 200–500 nm MP group. Notably, the enrichment became more pronounced in the long-term exposure samples than the short-term ones. Together with this process, the total abundance of bacteria, as well as the potential ARG-carrying bacteria, also increased in the N/MP-exposed groups, and the long-term N/MP exposure led more bacteria genera, such as Pseudomonas, Syntrophomonas, and Desulfotomaculum, to become closely associated with ARG variations. Meanwhile, the production of reactive oxygen species (ROS) induced by exposure to the 50–100 nm NPs and the 200–500 nm MPs was observed to increase bacterial membrane permeability, which might result in more bacteria becoming potential receptors of ARGs via the intra-bacterial community transfer of mobile genetic elements. Overall, the current study demonstrated that the presence of N/MPs in leachate promoted the propagation of ARGs due to their impacts on the bacterial community and cellular membrane permeability. These findings have important implications for understanding the environmental risks of the combined pollution of N/MPs and ARGs.
... Leachate released from landfills, is the main shelter for plastic waste, also an important repository of ARGs (Shi et al., 2020). NPs (nanoplastics)/MPs can promote the spread of ARGs in leachate. ...
... Under the dual influence of aging and biofilm formation, the surface morphology of MPs changes significantly, making them more suitable for bacterial survival and colonization. An increase in the ARB colonization rate promotes the spread of ARGs (Qiu et al., 2023;Shi et al., 2020;Su et al., 2021). Second, MPs can also affect the original bacterial community in landfill leachate and achieve selective enrichment of pathogenic bacteria and ARGs (Shi et al., , 2022a. ...
... Exposure to MPs can induce the production of excessive ROS (Shi et al., 2020). Additionally, the aging of MPs, the presence of other pollutants on MPs, and environmental stress can also cause ROS produced by bacteria (Wang et al., 2021b;Yuan et al., 2022). ...
... Bacteria in the plastisphere harbor different antibiotic resistance genes (ARGs) and pathogenic bacteria profiles than biofilms on natural substrates or bacteria in the surrounding aquatic environment (Wu et al., 2019). Furthermore, the abundance of ARGs (e.g., sul1, ermB) in MNP-associated biofilms was higher compared to bacteria in the surrounding environment (Wu et al., 2019;Shi et al., 2020). ARGs can be transferred to other (pathogenic) bacteria via horizontal gene transfer of mobile genetic elements, leading to antibiotic resistance in the receiving bacterial cell. ...
... Horizontal gene transfer was found to occur faster between microbes on MPs than between planktonic microbes (Arias-Andres et al., 2018). This was corroborated by the increase in abundance of ARGs and mobile genetic elements on MNPs over time (Imran et al., 2019;Shi et al., 2020). Considering that MNPs might serve as a vector for AMR and are ideal substrates for the long-distance transport of biofilms, MNPs might expose people to resistant microbes, for example, while swimming, hereby posing a human health threat. ...
... Since the size of MNPs affects the microbial composition of the MNP-associated biofilm, it may also affect the diversity or abundance of ARGs (Yang et al., 2019). NPs contain more reactive oxygen species (ROS) and microbes with a lower membrane permeability than MPs, which may lead to more bacterial cell damage (Shi et al., 2020). This lower membrane permeability found in NP-associated microbes may enhance AMR. ...
Micro- and nanoplastics (MNPs) are everywhere: in the air we breathe, in our food and in virtually every type of water. Currently, it is unknown whether, and to what extent, these MNPs are hazardous to human health. Identifying risks of physical and chemical aspects of MNPs has gained a lot of attention over the last few years, and efforts have been made to quantify these risks. In our opinion, the momentum delivered by these efforts should be used to highlight the relevance of including another important aspect of MNPs: their associated microbes. Although more and more studies describe MNP-associated microbes, the interplay between physical, chemical and microbiological aspects are lacking. Hazard identification parameters describing this interplay are crucial to risk assessment strategies, yet the majority of effort has been directed towards optimizing human exposure parameters. Here, we address the importance of including microbiological aspects of MNPs in the risk assessment of MNPs. Physical and chemical aspects of MNPs impact the diversity and abundance of microbes and antibiotic resistance genes (ARGs). In turn, environmental factors (e.g., UV radiation, antibiotics) may impact the microbial composition directly, or indirectly by impacting physical or chemical MNP aspects. Future efforts should be directed towards investigating this interplay in order to determine the effects of these dynamic outcomes on human health. We believe that elucidating these pieces of the puzzle is needed to ultimately perform a more holistic risk assessment of MNPs on human health.
... For instance, Shi et al. reported that exposure to 200-500 nm PS particles induced greater dissimilarity in microbial composition in municipal landfill leachate than 9.0-9.9 μm PS particles [54]. Additionally, Zhou et al. observed that PS nanoplastics (100 nm) decreased the abundance of nitrifiers and denitrifiers in activated sludge and suppressed the nitrification and denitrification genes, while PS microplastics (100 μm) showed no significant effects [55]. ...
... Similarly, Xu and Yu observed that 100 mg/kg of 10 μm PS microplastics significantly changed the profile of ARGs in earthworm guts [64]. Additionally, Shi et al. found that 200-500 nm PS particles increased the ARG abundances, including resistance genes for sulfonamide, aminoglycoside, macrolide, and beta-lactam [54]. The results potentially suggest that plastic particles with small sizes (e.g., <10 μm) may increase the abundance of ARGs in various environments. ...
... Qiu et al. reported that nano-alumina can damage bacterial cell membranes, promote the conjugative transfer of RP4 plasmid, and facilitate the horizontal transfer of multi-resistance genes between bacteria [65]. Similarly, nano-scale plastic particles were shown to elevate the intracellular oxidative levels and increase membrane permeability [54]. The nanoplastics could increase the production of reactive oxygen species, damaging the bacterial cell, and consequently increasing the membrane permeability, potentially causing more bacteria to become ARG receptors via the The asterisks indicate that the path coefficients are significant: *p < 0.05, **p < 0.01, and ***p < 0.001. ...
The wide application of plastics has led to the ubiquitous presence of nanoplastics and microplastics in terrestrial environments. However, few studies have focused on the mechanism underlying the effects of plastic particles on soil microbiomes and resistomes, especially the differences between nanoplastics and microplastics. This study investigated the microbiome and resistome in soil exposed to polystyrene microplastics (mPS) or nanoplastics (nPS) through 16S rRNA and shotgun metagenomic sequencing. Distinct microbial communities were observed between mPS and nPS exposure groups, and nPS exposure significantly changed the bacterial composition even at the lowest amended rate (0.01%, w/w). The abundance of antibiotic resistance genes (ARGs) in nPS exposure (1%) was 0.26 copies per cell, significantly higher than that in control (0.21 copies per cell) and mPS exposure groups (0.21 copies per cell). It was observed that nanoplastics, bacterial community, and mobile genetic elements (MGEs) directly affected the ARG abundance in nPS exposure groups, while in mPS exposure groups, only MGEs directly induced the change of ARGs. Streptomyces was the predominant host for multidrug in the control and mPS exposure, whereas the primary host was changed to Bacillus in nPS exposure. Additionally, exposure to nPS induced several bacterial hosts to exhibit possible multi-antibiotic resistance characteristics. Our results indicated that the effects of plastic particles on the soil microbial community were size-dependent, and nano-sized plastic particles exhibited more substantial impacts. Both microplastics and nanoplastics promoted ARG transfer and diversified their bacterial hosts. These findings bear implications for the regulation of plastic waste and ARGs.
... Ten target genes were analyzed in this study, including sulfonamide resistance genes (sul1 and sul2), aminoglycoside resistance genes (strB and aadA1), macrolide resistance gene (mefA), tetracycline resistance gene (tetM), beta-lactam resistance genes (bla OXA and bla TEM ) and integrase genes of class 1 and 2 integrons (intI1 and intI2). These target genes were frequently detected and had high abundances in leachate [38,47]. The abundances of target genes were detected by the real-time quantitative PCR (qPCR) with the CFX96 Touch system (BioRad, USA) according to previous publications [37]. ...
... The solution containing detached biofilm from MPs was collected, together with leachate, for ROS production measurement using ROS assay kit according to the manufacturer's direction. The levels of ROS were determined with a fluorescence-based method using 2, 7-dichlorodihydrofluorescein diacetate (DCFH-DA) [38]. The fluorescence intensity was monitored using a microplate reader (BioTek, USA) with 485 nm excitation and 525 nm emission filter. ...
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.
... Bacterial biofilm attachment on MPs has been found to facilitate ARGs spread through HGT (Zhang et al. 2020c). Additionally, studies on the effect of MPs on microbial communities revealed that MPs could increase bacterial abundance which might be another factor for ARG enrichments (Shi et al. 2020). However, most studies were conducted on spherical polyethylene microplastics (PE-MPs) while other shapes and materials are also detected in the environment. ...
Antibiotic resistance genes (ARGs) have emerged as a significant global health threat, contributing to fatalities worldwide. Wastewater treatment plants (WWTPs) and livestock farms serve as primary reservoirs for these genes due to the limited efficacy of existing treatment methods and microbial adaptation to environmental stressors. Anaerobic digestion (AD) stands as a prevalent biological treatment for managing sewage sludge and manure in these settings. Given the agricultural utility of AD digestate as biofertilizers, understanding ARGs’ fate within AD processes is essential to devise effective mitigation strategies. However, understanding the impact of various factors on ARGs occurrence, dissemination, and fate remains limited. This review article explores various AD treatment parameters and correlates to various resistance mechanisms and hotspots of ARGs in the environment. It further evaluates the dissemination and occurrence of ARGs in AD feedstocks and provides a comprehensive understanding of the fate of ARGs in AD systems. This review explores the influence of key AD parameters such as feedstock properties, pretreatments, additives, and operational strategies on ARGs. Results show that properties such as high solid content and optimum co-digestion ratios can enhance ARG removal, while the presence of heavy metals, microplastics, and antibiotics could elevate ARG abundance. Also, operational enhancements, such as employing two-stage digestion, have shown promise in improving ARG removal. However, certain pretreatment methods, like thermal hydrolysis, may exhibit a rebounding effect on ARG levels. Overall, this review systematically addresses current challenges and offers future perspectives associated with the fate of ARGs in AD systems.
Graphical Abstract
... Within the leachate microcosm, PE microplastics displayed a greater prevalence of ARGs compared to PP microplastics [4,35]. It is important to acknowledge that the presence of residual microplastics also influenced the dissemination of ARGs in sewage within the leachate solution [37]. The main origins of microplastics in terrestrial ecosystems were identified as sewage sludge, organic fertilizers, plastic film mulching, the deposition of airborne particles, and irrigation practices. ...
Landfill leachate contains antibiotic resistance genes (ARGs) and microplastics (MPs), making it an important reservoir. However, little research has been conducted on how ARGs are enriched on MPs and how the presence of MPs affects pathogens and ARGs in leachates and soil. MPs possess the capacity to establish unique bacterial populations and assimilate contaminants from their immediate surroundings, generating a potential environment conducive to the growth of disease-causing microorganisms and antibiotic resistance genes (ARGs), thereby exerting selection pressure. Through a comprehensive analysis of scientific literature, we have carried out a practical assessment of this topic. The gathering of pollutants and the formation of dense bacterial communities on microplastics create advantageous circumstances for an increased frequency of ARG transfer and evolution. Additional investigations are necessary to acquire a more profound comprehension of how pathogens and ARGs are enriched, transported, and transferred on microplastics. This research is essential for evaluating the health risks associated with human exposure to these pollutants.
... The sul genes were mainly associated with low abundant bacterial populations during the whole SRB treatment process, including the SRB strains Desulfosporosinus and Desulfotomaculum, and the acidophilic strain Acidiphilium added for the SRB treatment (< 0.1%; Fig. 1 and Fig. 4, Table S8). It has been demonstrated that Desulfosporosinus, Desulfotomaculum, and Acidiphilium are dominant ARG-associated genera, harboring ARGs such as the D-Ala-D-Lac ligase-encoding vanI and the bla ampicillin resistance genes (Inagaki et al. 1993;Shi et al. 2020). Combined with the previous discussion of microbial taxa variation ( Fig. 1 and S2), it is likely that the ARG enrichment process is finely tuned during the SRB treatment, resulting in dramatic and adaptative changes in microorganisms carrying ARGs. ...
Management of tailings at metal mine smelter sites can reduce the potential hazards associated with exposure to toxic metal(loid)s and residual organic flotation reagents. In addition, microbes in the tailings harboring multi-resistance genes (e.g., tolerance to multiple antimicrobial agents) can cause high rates of morbidity and global economic problems. The potential co-selection mechanisms of antibiotic resistance genes (ARGs) and metal(loid) resistance genes (MRGs) during tailings sulfate-reducing bacteria (SRB) treatment have been poorly investigated. Samples were collected from a nonferrous metal mine tailing site treated with an established SRB protocol and were analyzed for selected geochemical properties and high throughput sequencing of 16S rRNA gene barcoding. Based on the shotgun metagenomic analysis, the bacterial domain was dominant in nonferrous metal(loid)-rich tailings treated with SRB for 12 months. KEGGs related to ARGs and MRGs were detected. Thiobacillus and Sphingomonas were the main genera carrying the bacA and mexEF resistance operons, along with Sulfuricella which were also found as the main genera carrying MRGs. The SRB treatment may mediate the distribution of numerous resistance genes. KOs based on the metagenomic database indicated that ARGs (mexNW, merD, sul, and bla) and MRGs (czcABCR and copRS genes) were found on the same contig. The SRB strains (Desulfosporosinus and Desulfotomaculum), and the acidophilic strain Acidiphilium significantly contributed to the distribution of sul genes. The functional metabolic pathways related to siderophores metabolism were largely from anaerobic genera of Streptomyces and Microbacterium. The presence of arsenate reductase, metal efflux pump, and Fe transport genes indicated that SRB treatment plays a key role in the metal(loid)s transformation. Overall, our findings show that bio-treatment is an effective tool for managing ARGs/MRGs and metals in tailings that contain numerous metal(loid) contaminants.
... The interaction between MPs and microorganisms may allow the alteration in microbial communities and the occurrence of horizontal gene transfer and pathogen transmission. It has been demonstrated that changes in microbial communities on MPs in aquatic environments across different locations and the detection of pathogenic microorganisms in areas where they are not typically found [20,87,88]. Moreover, microbial communities colonized on MPs can be sensitive to temporal variations due to the changes in temperature, which may lead to different microbial composition results [44,45]. ...
Increasing studies of plastisphere have raised public concern about microplastics (MPs) as vectors for pathogens, especially in aquatic environments. However, the extent to which pathogens affect human health through MPs remains unclear, as controversies persist regarding the distinct pathogen colonization on MPs as well as the transmission routes and infection probability of MP-associated pathogens from water to humans. In this review, we critically discuss whether and how pathogens approach humans via MPs, shedding light on the potential health risks involved. Drawing on cutting-edge multidisciplinary research, we show that some MPs may facilitate the growth and long-range transmission of specific pathogens in aquatic environments, ultimately increasing the risk of infection in humans. We identify MP- and pathogen-rich settings, such as wastewater treatment plants, aquaculture farms, and swimming pools, as possible sites for human exposure to MP-associated pathogens. This review emphasizes the need for further research and targeted interventions to better understand and mitigate the potential health risks associated with MP-mediated pathogen transmission.
... Proteobacteria, the largest and most diverse phylum of bacteria, were frequently reported to exist in landfills, leachates, soil, WWTPs, and other environments and were generally associated with degradable or nondegradable pollutants such as antibiotics and ARGs (Spain et al. 2009;Yang and Song 2019;Shi et al. 2020;Yang et al. 2021;Langbehn et al. 2021). In this study, Ottowia, Thauera, Rhodanobacter, Aminobacter, Lysobacter, Isosphaera, Castellaniella, Thermomonas, Hyphomicrobium, g__ unclassified_f__Comamonadaceae, and g__unclassified_f__ Methylophagaceae, which belong to Proteobacteria, were closely related to the target genes. ...
The mechanism of antibiotic resistance (AR) development in an activated sludge system under tetracycline (TC) pressure was discussed and analyzed. According to the variation of macro-factors, including TC, COD, TN, TP, NH3-N, pH, heavy metals, and reactor settings, the tet genes respond accordingly. Consequently, the enrichment sites of tet genes form an invisible AR selection zone, where AR microorganisms thrive, gather, reproduce, and spread. The efflux pump genes tetA and tetB prefer anaerobic environment, while ribosome protective protein genes tetM, tetO, tetQ, tetT, and tetW were more concentrated in aerobic situations. As a corresponding micro-effect, different types of tet genes selected the corresponding dominant bacteria such as Thauera and Arthrobacter, suggesting the intrinsic relationship between tet genes and potential hosts. In summary, the macro-response and micro-effect of tet genes constitute an interactive mechanism with tet genes as the core, which is the crucial cause for the continuous development of AR. This study provides an executable strategy to control the development of AR in actual wastewater treatment plants from the perspective of macro-factors and micro-effects.
... Besides chemical contaminants, microbes from the environmental systems can colonise the surfaces of MPs, forming biofilms (Zettler et al., 2013;Oberbeckmann & Labrenz, 2020). The interaction between MPs and microorganisms in the environment gives rise to extracellular polymeric substances (EPSs) (Johansen et al., 2018(Johansen et al., , 2019Shi et al., 2020;Yang et al., 2020;Kesy et al., 2021). EPSs determine the structural and functional integrity of the biofilms formed and are considered a key component that may affect the morphology, density and chemical properties of MPs. ...
Microplastics (MPs) are becoming ubiquitous, and their environmental fate is becoming an issue of concern. Our review aims to synthesize current knowledge status and provide future perspectives regarding the vector effect of MPs for chemical contaminants and biological agents. The evidence in the literature indicates that MPs are a vector for persistent organic pollutants (POPs), metals and pharmaceuticals. Concentrations of chemical contaminant in orders of six-fold higher on MPs surfaces than in the surrounding environmental waters have been reported. Chemical pollutants such as perfluoroalkyl substances (PAFSs), hexachlorocyclohexane (HCHs) and polycyclic aromatic hydrocarbons (PAHs), exhibiting polarities in the range of 3.3–9 are the commonest chemicals reported on MP surfaces. Regarding metals on MPs including chromium (Cr), lead (Pb), cobalt (Co), the presence of C–O and N–H in MPs promote a relatively high adsorption of these metals onto MP surfaces. Regarding pharmaceuticals, not much has been done, but a few studies indicate that commonly used drugs such as ibuprofen, ibuprofen, diclofenac, and naproxen have been associated with MPs. There is sufficient evidence supporting the claim that MPs can act as vectors for viruses, bacterial and antibiotic-resistant bacteria and genes, and MPs act to accelerate horizontal and vertical gene transfer. An area that deserves urgent attention is whether MPs can act as vectors for invertebrates and vertebrates, mainly non-native, invasive freshwater species. Despite the ecological significance of invasive biology, little research has been done in this regard. Overall, our review summarises the state of the current knowledge, identifies critical research gaps and provides perspectives for future research.
... Moreover, because MPs increase cell membrane permeability, ARGs might be more readily available to bacteria. As a result, the transfer of MGEs may lead to an increase in bacteria that could become receptors for the ARGs (Shi et al., 2020). The transfer occurs through ARG's spread in the environment through vertical gene transfer by transmitting genetic information during prokaryotic cell division and HGT driven by mobile genetic elements (MGEs), involving bacteriophages, insertion sequences, integrons, membrane vesicles, plasmids, and transposons (Abe et al., 2020;Lu et al., 2021;Wang et al. 2021a, b;Wu et al., 2019;Yuan et al., 2022;Zhang et al., 2021a). ...
Antibiotic resistance genes (ARGs) and microplastics (MPs) are one of the major threats, representing a pressing concern to the environment and human health. MPs have been shown to influence bacterial growth and community composition, which could have an impact on the spread of ARGs in the environment. Antibiotic use has resulted in mutated genes in bacteria, and as a result, they can reduce the efficacy of antibiotic therapies, necessitating the use of more of them. Humans produce a significant amount of waste, and global quantities are constantly increasing, resulting in the colonization of many antibiotic resistance bacteria in MPs, which have been turned into a reservoir for ARGs. This chapter highlights the main sources of MPs in the environment, mechanisms of transfer, relationships, and interactions between MPs and ARGs. This revision of the literature aims more specifically to provide the potential implications of the antibiotic resistome of the plastisphere for human health.Graphical Abstract
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KeywordsMicroplasticsAntibiotic resistance genesEnvironment
Human health
Microplastics (MPs) are becoming progressively widespread in the surrounding and are regarded as vectors of antibiotic resistance genes (ARGs). Soils of various properties carry large amounts of microplastics and ARGs. However, a thorough research evaluating the impact of different regions of China in evolving antibiotic resistome in soil MPs is insufficient. Here, we engaged a massive investigation by putting Polyvinyl chloride microplastics (PVC) into soil in 20 provinces of China which have different physical and chemical properties. The results showed that PVC could significantly affect soil bacterial community structure and ARGs abundance. Structural equation models showed that the addition of PVC changed the characteristics of the soil, which in turn influenced the bacterial community in the soil (which included ARG-containing bacterial hosts) and, ultimately, the relative abundance of ARGs. This work improves our comprehension of the effects of microplastics on the proliferation and hosts of ARGs in various soil environments, and it serves as a crucial reference for future plastic consumption and disposal.
The microplastisphere is a dense consortium of metabolically active microorganisms that develops on the surface of microplastics. Since the discovery that it harbors antibiotic resistance genes (ARGs), there has been a quest to decipher the relationship between ARG occurrences and selective enrichment with plastic types, which is important to understand their fate in diverse environmental settings. Nonetheless, it remains a neglected topic, and this developing field of microplastics research could benefit from a comprehensive review to acquire a deeper understanding of the most recent advances and drive scientific progress. Accordingly, the goal of this review is to critically discuss and provide an in-depth assessment of the evidence of ARGs' global nature in microplastispheres, as well as explore factors that influence them directly and indirectly, highlighting important concerns and knowledge gaps throughout the article. By comprehensively covering them, we underscore the potential environmental implications associated with microplastisphere ARGs. From our analysis, it emerged that microplastisphere ARGs are likely to be impacted not only by differences in microplastic types and characteristics but also by how their environments are shaped by other agents such as physiochemical properties, socioeconomic factors, and contaminants coexistence, influencing ARG subtype, incidence, abundance, and selective enrichment. The intricate relationship of microplastisphere ARGs to environmental conditions and plastic types calls for multilevel investigations to clearly assess the environmental fate of microplastics. We anticipate that this review could assist researchers in strengthening their foundation and identifying efforts to advance knowledge in this research field.
The microplastisphere is a dense consortium of metabolically active microorganisms that develops on the surface of microplastics. Since the discovery that it harbors antibiotic resistance genes (ARGs), there has been a quest to decipher the relationship between ARG occurrences and selective enrichment with plastic types, which is important to understand their fate in diverse environmental settings. Nonetheless, it remains a neglected topic, and this developing field of microplastics research could benefit from a comprehensive review to acquire a deeper understanding of the most recent advances and drive scientific progress. Accordingly, the goal of this review is to critically discuss and provide an in-depth assessment of the evidence of ARGs' global nature in microplastispheres, as well as explore factors that influence them directly and indirectly, highlighting important concerns and knowledge gaps throughout the article. By comprehensively covering them, we underscore the potential environmental implications associated with microplastisphere ARGs. From our analysis, it emerged that microplastisphere ARGs are likely to be impacted not only by differences in microplastic types and characteristics but also by how their environments are shaped by other agents such as physiochemical properties, socioeconomic factors, and contaminants coexistence, influencing ARG subtype, incidence, abundance, and selective enrichment. The intricate relationship of microplastisphere ARGs to environmental conditions and plastic types calls for multilevel investigations to clearly assess the environmental fate of microplastics. We anticipate that this review could assist researchers in strengthening their foundation and identifying efforts to advance knowledge in this research field.
Environmentally-friendly management of landfill leachate (LL) poses a challenge, and LL is usually co-treated with municipal wastewater in wastewater treatment plants (WWTPs). The extent to which the co-treatment of LL and municipal wastewater influences the spread of antibiotic resistance (AR) in the environment has not been examined to date. Two WWTPs with similar wastewater composition and technology were studied. Landfill leachate was co-treated with wastewater in one of the studied WWTPs. Landfill leachate, untreated and treated wastewater from both WWTPs, and river water sampled upstream and downstream from the wastewater discharge point were analyzed. Physicochemical parameters, microbial diversity, and antibiotic resistance genes (ARGs) abundance were investigated to determine the impact of LL co-treatment on chemical and microbiological contamination in the environment. Landfill leachate increased pollutant concentrations in untreated wastewater and river water. Cotreatment of LL and wastewater could affect the abundance and diversity of microbial communities and the interactions between microbial species. Co-treatment also decreased the stability of microbial co-occurrence networks in the examined samples. The mexF gene was identified as a potential marker of environmental pollution with LL. This is the first study to explore the impact of LL on the occurrence of AR determinants in wastewater and rivers receiving effluents.
Microplastics (MPs) pollution is a pressing environmental issue for aquatic ecosystems. Landfill leachate is an important contributor of MPs and antibiotic resistant genes (ARGs). However, there are few studies on the colonization of ARGs and pathogens on MPs in leachate. This study conducted incubation experiments with polyethylene terephthalate (PET) and polypropylene (PP) MPs in landfill leachate which were about 3-5 years old (PL) and 5-10 years old (AL). After incubation, the bacterial cells colonized and grew on the surface of MPs, inducing the increase of oxygenated oxygen functional groups (e.g., hydroxyl, carbonyl) on the MPs surface. Real-time PCR indicated that MPs selectively enriched ARGs, such as genes tetM, tetC, mcr-1, aac(6')-Ib-cr, blaTEM and blaSHV in leachate. The diversity of bacterial communities on MPs was significantly increased in AL leachate, but decreased in PL leachate. The differences in bacterial communities in MPs biofilms were related to the type of MPs. Compared with AL leachate, the abundance of Chloroflexi increased by 15.7% on the PET, and the abundance of Acidobacteriota increased by 6.23 fold on the PP. The abundance of Firmicutes increased from 20.7% in PL leachate to 65.8% and 60.7% on PET and PP, respectively. Additionally, pathogens were observed to be more abundant on MPs compared to leachate. In particular, pathogens (Staphylococcus, Streptococcus, Enterobacter and Rhodococcus) associated with sul1 and sul2 were generally present at higher levels on MPs than in the surrounding leachate. These results provide significant implications for understanding the health risk of MPs in the environment.
Microorganisms colonizing the surfaces of microplastics form a plastisphere in the environment, which captures miscellaneous substances. The plastisphere, owning to its inherently complex nature, may serve as a "Petri dish" for the development and dissemination of antibiotic resistance genes (ARGs), adding a layer of complexity in tackling the global challenge of both microplastics and ARGs. Increasing studies have drawn insights into the extent to which the proliferation of ARGs occurred in the presence of micro/nanoplastics, thereby increasing antimicrobial resistance (AMR). However, a comprehensive review is still lacking in consideration of the current increasingly scattered research focus and results. This review focuses on the spread of ARGs mediated by microplastics, especially on the challenges and perspectives on determining the contribution of microplastics to AMR. The plastisphere accumulates biotic and abiotic materials on the persistent surfaces, which, in turn, offers a preferred environment for gene exchange within and across the boundary of the plastisphere. Microplastics breaking down to smaller sizes, such as nanoscale, can possibly promote the horizontal gene transfer of ARGs as environmental stressors by inducing the overgeneration of reactive oxygen species. Additionally, we also discussed methods, especially quantitatively comparing ARG profiles among different environmental samples in this emerging field and the challenges that multidimensional parameters are in great necessity to systematically determine the antimicrobial dissemination risk in the plastisphere. Finally, based on the biological sequencing data, we offered a framework to assess the AMR risks of micro/nanoplastics and biocolonizable microparticles that leverage multidimensional AMR-associated messages, including the ARGs' abundance, mobility, and potential acquisition by pathogens.
The leakage of landfill leachate (LL) into environmental media would be happened even in the sanitary/controlled landfill, due to the deterioration of geomembrane and the blockage of drainage system after long-term operation. Considering the complex composition and high concentration of pollutants in LL, its toxicity assessment should be conducted as a whole liquid contaminant. Therefore, the impacts of LL on Caenorhabditis elegans (C. elegans) were investigated under the condition of different exposure time and exposure volume fraction (EVF). The stimulating effects on locomotion behavior and growth of C. elegans were observed after acute (24 h) exposure to LL, which were increased firstly and then decreased with the increase of EVF. Meanwhile, the intestinal barrier was not affected by LL, and levels of reactive oxygen species (ROS) and cell apoptosis significantly decreased. However, stimulation and inhibition effects on locomotion behavior and growth of C. elegans were observed when subacute (72 h) exposure to 0.25%-0.5% and 1%-4% of LL, respectively. The intestinal injury index and levels of ROS and cell apoptosis significantly increased when EVF were 2% and 4%. Although the acute exposure of LL had resulted in obviously biological adaptability and antioxidant defense in C. elegans, the protective mechanisms failed to be induced as the exposure time increased (subacute exposure). The toxic effects were confirmed by the down-regulation of genes associated with antioxidant defense and neurobehavior, accompanied by the up-regulation of intestinal injury and cell apoptosis related genes. Moreover, the disturbance of metabolic pathways that associated with locomotion behaviors, growth, and antioxidant defense provided good supplementary evidence for the confirmation of oxidative stress in C. elegans. The research results verified the potential of C. elegans as model organism to determine the complex toxic effects of LL.
Microplastics, fragmented plastic particles with a maximum dimension <5 mm, are an emerging contaminant of concern that can also serve as a vector of other chemical and biological contaminants. Compared to chemical contaminants, the potential of microplastics to adsorb biological microcontaminants such as antibiotic resistance genes, small interference RNAs, and pathogenic viruses is not well understood. Many current microplastic studies are based in the aquatic environment (freshwater, seawater, and wastewater), even though the terrestrial environment is considered both an important sink and source of microplastics. Microplastics co-occur with biological microcontaminants in many terrestrial environments including agricultural soils, where biosolids containing both contaminants are often applied as a soil amendment. Recent research suggests that microplastics in these environments can increase gene persistence and flow, which could have unintended downstream consequences for environmental microbiome health and resilience. Antibiotic resistance genes and silencing RNAs bound to microplastics, for example, have the potential to increase resistance and alter gene expression in environmental bacteria, respectively. This review evaluates the sources and pathways of microplastics and biological microcontaminants in the terrestrial environment as well as potential sorption mechanisms that can encourage long-range transport and persistence. Novel sources of biological microcontaminants are considered, and the role of microplastics in promoting the persistence and flow of biological microcontaminants evaluated. Finally, future research directions are suggested to increase understanding of the mechanisms that drive the fate and transport of microplastic-biological microcontaminant complexes in the terrestrial environment and better inform risk management.
A significant amount of plastic waste is generated each year on a global scale, in which the maximum quantity of plastic waste is typically dumped in landfills in various parts of the world. Moreover, dumping plastic waste in landfills cannot address the issue of proper disposal; it simply delays the process. Exploiting waste resources entails environmental hazards because plastic wastes buried in landfills gradually break down into Microplastics (MPs) due to physical, chemical, and biological effects. The possibility of landfill leachate as a source of MPs in the environment has not received much attention. Without systematic treatment, MPs in leachate increase the risk to human health and environmental health since they contain dangerous and toxic pollutants and antibiotic resistance genes transmitted by leachate vectors. Due to their severe environmental risks, MPs are now widely recognized as emerging pollutants. Therefore, the composition of MPs in landfill leachate and the interaction of MPs with other hazardous contaminants are summarised in this review. The available potential mitigation or treatment methods of MPs in landfill leachate as of now, along with the drawbacks and challenges of the present leachate treatment for eliminating MPs, are described in this review. Since it is unclear how MPs will be removed from the current leachate facilities, it is crucial to develop innovative treatment facilities as quickly as possible. Finally, the areas that require more research to provide complete solutions to the persistent problem of plastic debris are discussed.
Micro and nano-plastics (MNPs) have been considered one of the major emerging contaminants that require immediate attention. Their potential impact on the natural ecosystems is yet to be understood, especially their associations with other contaminants like heavy metals and organisms essential for the sustenance of life, i.e., microbes. Microplastics (MPs) also act as sources and carriers of pollutants, similar to macro and mesoplastics, that leach harmful chemicals such as Polybrominated Diphenyl Ethers (PBDEs), Pharmaceutical and Personal Care Products (PPCPs), Endocrine Disruptive Chemicals (EDCs), etc. They also behave like super sponge materials which adsorb microbes such as antibiotic resistance bacteria (ARBs), and coronavirus, making their concentration much higher than the ambient environment. Among these microbes, heavy metal-resistance (MRGs) and antibiotic-resistance genes (ARGs) carry immense significance. The present study provides an in-depth review analysis of the works published related to the association of MPs to heavy metals and ARGs. 1526 articles were investigated after the dataset was subjected to a three-stage screening process. A scientometric analysis revealing details about the most productive and influential journals, co-authorship details, most influential publications, most cited keywords, and most active countries in the research domain was conducted. This provided significant information regarding various aspects of the published works of literature. Subsequently, a qualitative discussion was carried out wherein a detailed discussion with regard to the trends in research on sub-areas in the broad domain was conducted. This resulted in identifying the gaps in the available literature, which paved the way for providing a framework for future research. Through this study, it is expected that the readers will be exposed to a summary of the overall research that has been conducted to date, and the manuscript will act as a guide for future research.
MPs carrying ARGs can travel between freshwater and seawater due to intensive land-sea interaction in onshore marine aquaculture zones (OMAZ). However, the response of ARGs in plastisphere with different biodegradability to freshwater-seawater shift is still unknown. In this study, ARG dynamics and associated microbiota on biodegradable poly (butyleneadipate-co-terephthalate) (PBAT) and non-biodegradable polyethylene terephthalate (PET) MPs were investigated through a simulated freshwater-seawater shift. The results exhibited that freshwater-seawater shift significantly influenced ARG abundance in plastisphere. The relative abundance of most studied ARGs decreased rapidly in plastisphere after they entered seawater from freshwater but increased on PBAT after MPs entered freshwater from seawater. Besides, the high relative abundance of multi-drug resistance (MDR) genes occurred in plastisphere, and the co-change between most ARGs and mobile genetic elements indicated the role of horizontal gene transfer on ARG regulation. Proteobacteria was dominant phylum in plastisphere and the dominant genera, such as Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium, Afipia, Gemmobacter and Enhydrobacter, were significantly associated with qnrS, tet and MDR genes in plastisphere. Moreover, after MPs entered new water environment, the ARGs and microbiota genera in plastisphere changed significantly and tended to converge with those in receiving water. These results indicated that MP biodegradability and freshwater-seawater interaction influenced potential hosts and distributions of ARGs, of which biodegradable PBAT posed a high risk in ARG dissemination. This study would be helpful for understanding the impact of biodegradable MP pollution on spread of antibiotic resistance in OMAZ.
Although clinical settings play a major role in the current global dissemination of antibiotic resistance, once antibiotic resistance bacteria and genes are released into the environment, their fate will be subject to complex ecological processes. One of the processes prevalent in microbial communities - horizontal gene transfer - can largely facilitate the dissemination of antibiotic resistance genes (ARGs) across phylogenetic and ecological boundaries. Especially, plasmid transfer has aroused increasing concern as it has been proved a significant role in promoting ARG dissemination. As a multi-step process, plasmid transfer can be influenced by various factors, among which those stresses caused by environmental pollutants are important elements affecting the plasmid mediated ARG transfer in the environment. In fact, diverse traditional and emerging pollutants are continuously entering the environment nowadays, as evidenced by the global occurrence of pollutants like metals and pharmaceuticals in aquatic and terrestrial systems. It is therefore imperative to understand to what extent and in which way the plasmid mediated ARG dissemination can be influenced by these stresses. Over the past decades, numerous research endeavours have been made to understand the plasmid mediated ARG transfer under various environmental relevant pressures. In this review, progress and challenges of studies on environmental stress regulating plasmid mediated ARG dissemination will be discussed, with specific focus on emerging pollutants like antibiotics and non-antibiotic pharmaceuticals, metals and their nanoparticles, disinfectants and disinfection by-products, as well as the emerging particulate matter like microplastics. Despite the previous efforts, we are still lacking insights into the in situ plasmid transfer under environmental stresses, which can be addressed by future studies considering environmental relevant pollution status and multi-species microbial communities. We believe that future development of standardized high-throughput screening platforms will assist in rapidly identifying which pollutants enhance plasmid transfer and also which ones may block such gene transfer processes.
As the global concern over plastic pollution grows, efforts are underway to find environmentally friendly alternatives to traditional plastics. Bioplastics are being extensively researched and developed as a possible solution. This study compared the impact of two bioplastics, polylactic acid (PLA) and polyhydroxy butyrate (PHB), on the proliferation of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) during anaerobic digestion (AD). Both bioplastics (250-500 particles) could be degraded to a certain extent over 79 days, as indicated by higher methane production than the control without bioplastic particles. The PHB 500 reactor showed the highest methane yield along with the highest biodegradation efficiency (91 %) than other reactors amended with PHB and PLA particles. The highest ARG and MGE abundances were also observed in PLA 500, and the lowest ARG abundance was in PLA 250. Conversely, PHB reactors showed a relatively lower ARG abundance than the control. The correlation analysis suggested that most ARGs were positively correlated with PLA and negatively correlated with PHB (except for tetA, tetB, and tetX). Moreover, a correlation between MGEs and ARGs in PLA and PHB reactors was revealed by correlation analysis. These results show that AD responds differently to the different types/levels of bioplastics, which can ultimately influence the behavior of ARG proliferation. Thus, bioplastics may also pose a potential risk for spreading antibiotic resistance. These findings can be used as a basis for setting environmental standards for bioplastics and creating monitoring and control measures to prevent potential negative impacts on public health.
Nano/microplastics (NPs/MPs) in sewage sludge can induce oxidative stress to the anaerobic digestion (AD) and also proliferate antibiotic resistance genes (ARGs). Recently, granular activated carbon (GAC) has been used as an additive to enhance methane production in AD via direct interspecies electron transfer (DIET); however, its impact on AD exposed to NPs/MPs is yet to be studied. This study examined the effect of GAC (5 and 15 g/L) on sludge AD exposed to 150 µg/L of polystyrene nanoplastics (PsNPs). PsNPs decreased methane yield by 32.3% due to elevated levels of reactive oxygen species. However, GAC addition counteracted this adverse effect and improved methane production, attributed to the potential enrichment of DIET-active microbes and the adsorption of PsNPs by GAC. Moreover, GAC reduced the total abundance of ARGs, which was increased by PsNPs exposure. Thus, GAC can provide dual benefits in mitigating methanogenic inhibition caused by PsNPs and ARG spread.
Although the fates of microplastics (0.1-5 mm) in marine environments and freshwater are increasingly studied, little is known about their vector effect in wastewater treatment plants (WWTPs). Previous studies have evaluated the accumulation of antibiotic resistance genes (ARGs) on microplastics, but there is no direct evidence for the selection and horizontal transfer of ARGs on different microplastics in WWTPs. Here, we show biofilm formation as well as bacterial community and ARGs in these biofilms grown on four kinds of microplastics via incubation in the aerobic and anaerobic tanks of a WWTP. Microplastics showed differential capacities for bacteria and ARGs enrichment, differing from those of the culture environment. Furthermore, ARGs in microplastic biofilms were horizontally transferred at frequencies higher than those in water samples in both tanks. Therefore, microplastics in WWTPs can act as substrates for horizontal transfer of ARGs, potentially causing a great harm to the ecological environment and adversely affecting human health.
Over the last five decades, plastics production has increased as a consequence of their use in strategic sectors causing damage on aquatic ecosystems. In this context, biodegradable plastics have emerged as an ecological alternative because they are easily degradable in the environment. Despite the recent advances in the field of plastic ecotoxicology, the ecological impact of secondary nanoplastics (nanoplastics resulting from natural degradation of micro and macro plastics) in the environment remains poorly understood. Here, we have investigated the effects of secondary nanoplastics of polyhydroxybutyrate (PHB), a biodegradable plastic, on three representative organisms of aquatic ecosystems. Secondary PHB-nanoplastics were produced from PHB-microplastics by abiotic degradation under environmentally representative conditions. Secondary PHB-nanoplastics induced a significant decrease in cellular growth and altered relevant physiological parameters in all organisms. We investigated whether the observed toxicity was exerted by PHB-nanoplastics themselves or by other abiotic degradation products released from PHB-microplastics. An experiment was run in which PHB-nanoplastics were removed by ultrafiltration; the resulting supernatant was not toxic to the organisms, ruling out the presence of toxic chemicals in the PHB-microplastics. In addition, we have performed a complete physicochemical characterization confirming the presence of secondary PHB-nanoplastics in the 75–200 nm range. All results put together indicated that secondary PHB-nanoplastics released as a consequence of abiotic degradation of PHB-microplastics were harmful for the tested organisms, suggesting that biodegradable plastic does not mean safe for the environment in the case of PHB.
Gephi is an open source software for graph and network analysis. It uses a 3D render engine to display large networks in real-time and to speed up the exploration. A flexible and multi-task architecture brings new possibilities to work with complex data sets and produce valuable visual results. We present several key features of Gephi in the context of interactive exploration and interpretation of networks. It provides easy and broad access to network data and allows for spatializing, filtering, navigating, manipulating and clustering. Finally, by presenting dynamic features of Gephi, we highlight key aspects of dynamic network visualization.
Plastics have been accumulated offshore and in the deep oceans at an unprecedented scale. Microbial communities have colonized the plastisphere, which has become a reservoir for both antibiotic and metal resistance genes (ARGs and MRGs). This is the first analysis of the diversity, abundance, and co-occurrence of ARGs and MRGs, and their relationships within the microbial community, using metagenomic data of plastic particles observed in the North Pacific Gyre obtained from the National Centre for Biotechnology Information Sequence Read Archive database. The abundance of ARGs and MRGs in microbial communities on the plastics were in the ranges 7.07 × 10 −4-1.21 × 10 −2 and 5.51 × 10 −3-4.82 × 10 −2 copies per 16S rRNA, respectively. Both the Shannon-Wiener indices and richness of ARGs and MRGs in plastics microbiota were significantly greater than those of ARGs and MRGs in seawater microbiota in the North Pacific Gyre via one-way analysis of variance. Multidrug resistance genes and multi-metal resistance genes were the main classes of genes detected in plastic microbiota. There were no significant differences in the abundance or diversity of ARGs and MRGs between macroplastics biota and microplastics biota, indicating that particle size had no effect on resistance genes. Procrustes analysis suggested that microbial community composition was the determining factor of the ARG profile but not for MRG. Some ARGs and MRGs had a higher incidence of non-random co-occurrence, suggesting that the co-effects of selection for antibiotic or metal resistance are important factors influencing the resistome of the microbiota on the plastic particles.
Plastics have been accumulated offshore and in the deep oceans at an unprecedented scale. Microbial communities have colonized the plastisphere, which has become a reservoir for both antibiotic and metal resistance genes (ARGs and MRGs). This is the first analysis of the diversity, abundance, and co-occurrence of ARGs and MRGs, and their relationships within the microbial community, using metagenomic data of plastic particles observed in the North Pacific Gyre obtained from the National Centre for Biotechnology Information Sequence Read Archive database. The abundance of ARGs and MRGs in microbial communities on the plastics were in the ranges 7.07 × 10⁻⁴–1.21 × 10⁻² and 5.51 × 10⁻³–4.82 × 10⁻² copies per 16S rRNA, respectively. Both the Shannon-Wiener indices and richness of ARGs and MRGs in plastics microbiota were significantly greater than those of ARGs and MRGs in seawater microbiota in the North Pacific Gyre via one-way analysis of variance. Multidrug resistance genes and multi-metal resistance genes were the main classes of genes detected in plastic microbiota. There were no significant differences in the abundance or diversity of ARGs and MRGs between macroplastics biota and microplastics biota, indicating that particle size had no effect on resistance genes. Procrustes analysis suggested that microbial community composition was the determining factor of the ARG profile but not for MRG. Some ARGs and MRGs had a higher incidence of non-random co-occurrence, suggesting that the co-effects of selection for antibiotic or metal resistance are important factors influencing the resistome of the microbiota on the plastic particles.
Background:
Taxonomic classification of marker-gene sequences is an important step in microbiome analysis.
Results:
We present q2-feature-classifier ( https://github.com/qiime2/q2-feature-classifier ), a QIIME 2 plugin containing several novel machine-learning and alignment-based methods for taxonomy classification. We evaluated and optimized several commonly used classification methods implemented in QIIME 1 (RDP, BLAST, UCLUST, and SortMeRNA) and several new methods implemented in QIIME 2 (a scikit-learn naive Bayes machine-learning classifier, and alignment-based taxonomy consensus methods based on VSEARCH, and BLAST+) for classification of bacterial 16S rRNA and fungal ITS marker-gene amplicon sequence data. The naive-Bayes, BLAST+-based, and VSEARCH-based classifiers implemented in QIIME 2 meet or exceed the species-level accuracy of other commonly used methods designed for classification of marker gene sequences that were evaluated in this work. These evaluations, based on 19 mock communities and error-free sequence simulations, including classification of simulated "novel" marker-gene sequences, are available in our extensible benchmarking framework, tax-credit ( https://github.com/caporaso-lab/tax-credit-data ).
Conclusions:
Our results illustrate the importance of parameter tuning for optimizing classifier performance, and we make recommendations regarding parameter choices for these classifiers under a range of standard operating conditions. q2-feature-classifier and tax-credit are both free, open-source, BSD-licensed packages available on GitHub.
Plastic debris is an environmentally persistent and complex contaminant of increasing concern. Understanding the sources, abundance and composition of microplastics present in the environment is a huge challenge due to the fact that hundreds of millions of tonnes of plastic material is manufactured for societal use annually, some of which is released to the environment. The majority of microplastics research to date has focussed on the marine environment. Although freshwater and terrestrial environments are recognised as origins and transport pathways of plastics to the oceans, there is still a comparative lack of knowledge about these environmental compartments. It is highly likely that microplastics will accumulate within continental environments, especially in areas of high anthropogenic influence such as agricultural or urban areas. This review critically evaluates the current literature on the presence, behaviour and fate of microplastics in freshwater and terrestrial environments and, where appropriate, also draws on relevant studies from other fields including nanotechnology, agriculture and waste management. Furthermore, we evaluate the relevant biological and chemical information from the substantial body of marine microplastic literature, determining the applicability and comparability of this data to freshwater and terrestrial systems. With the evidence presented, the authors have set out the current state of the knowledge, and identified the key gaps. These include the volume and composition of microplastics entering the environment, behaviour and fate of microplastics under a variety of environmental conditions and how characteristics of microplastics influence their toxicity. Given the technical challenges surrounding microplastics research, it is especially important that future studies develop standardised techniques to allow for comparability of data. The identification of these research needs will help inform the design of future studies, to determine both the extent and potential ecological impacts of microplastic pollution in freshwater and terrestrial environments.
Antibiotic resistance genes (ARGs) have moved from the environmental resistome into human commensals and pathogens, driven by human selection with antimicrobial agents. These genes have increased in abundance in humans and domestic animals, to become common components of waste streams. Estuarine habitats lie between terrestrial/freshwater and marine ecosystems, acting as natural filtering points for pollutants. Here, we have profiled ARGs in sediments from 18 estuaries over 4,000 km of coastal China using high-throughput quantitative polymerase chain reaction, and investigated their relationship with bacterial communities, antibiotic residues and socio-economic factors. ARGs in estuarine sediments were diverse and abundant, with over 200 different resistance genes being detected, 18 of which were found in all 90 sediment samples. The strong correlations of identified resistance genes with known mobile elements, network analyses and partial redundancy analysis all led to the conclusion that human activity is responsible for the abundance and dissemination of these ARGs. Such widespread pollution with xenogenetic elements has environmental, agricultural and medical consequences.
We describe the occurrence of blaVIM-2 in 10 carbapenem-resistant Pseudomonas monteilii strains isolated from different clinical samples in our hospital in Northern Spain. All the blaVIM-2-harbouring P. monteilii isolates possessed a class 1 integron, with the cassette array [intI1_blaVIM-2_aac(6' )-Ib_qacEΔ1_sul1]. Our results show the emergence of VIM-2-producing multidrug-resistant species other than P. aeruginosa or P. putida in a Spanish hospital. P. monteilii, though sporadically isolated, should also be considered as an important MBLs reservoir.
Copyright © 2014, American Society for Microbiology. All Rights Reserved.
Ancient and diverse antibiotic resistance genes (ARGs) have previously been identified from soil, including genes identical to those in human pathogens. Despite the apparent overlap between soil and clinical resistomes, factors influencing ARG composition in soil and their movement between genomes and habitats remain largely unknown. General metagenome functions often correlate with the underlying structure of bacterial communities. However, ARGs are proposed to be highly mobile, prompting speculation that resistomes may not correlate with phylogenetic signatures or ecological divisions. To investigate these relationships, we performed functional metagenomic selections for resistance to 18 antibiotics from 18 agricultural and grassland soils. The 2,895 ARGs we discovered were mostly new, and represent all major resistance mechanisms. We demonstrate that distinct soil types harbour distinct resistomes, and that the addition of nitrogen fertilizer strongly influenced soil ARG content. Resistome composition also correlated with microbial phylogenetic and taxonomic structure, both across and within soil types. Consistent with this strong correlation, mobility elements (genes responsible for horizontal gene transfer between bacteria such as transposases and integrases) syntenic with ARGs were rare in soil by comparison with sequenced pathogens, suggesting that ARGs may not transfer between soil bacteria as readily as is observed between human pathogens. Together, our results indicate that bacterial community composition is the primary determinant of soil ARG content, challenging previous hypotheses that horizontal gene transfer effectively decouples resistomes from phylogeny.
We investigated the effects of three sizes of polystyrene (PS) micro-beads (0.05, 0.5, and 6 µm diameter) on the survival, development, and fecundity of the copepod Tigriopus japonicus using acute and chronic toxicity tests. T. japonicus ingested and egested all three sizes of PS beads used and exhibited no selective feeding when phytoplankton were added. The copepods (nauplius and adult females) survived all sizes of PS beads and the various concentrations tested in the acute toxicity test for 96 h. In the two-generation chronic toxicity test, 0.05-µm PS beads at a concentration greater than 12.5 µg/mL caused the mortality of nauplii and copepodites in the F0 generation and even triggered mortality at a concentration of 1.25 µg/mL in the next generation. In the 0.5 µm PS bead treatment, despite there being no significant effect on the F0 generation, the highest concentration (25 µg/mL) induced a significant decrease in survival compared with the control population in the F1 generation. The 6 µm PS beads did not affect the survival of T. japonicus over two generations. The 0.5 and 6 µm PS beads caused a significant decrease in fecundity at all concentrations. These results suggest that microplastics such as micro- or nano-sized PS beads may have negative impacts on marine copepods.
The major potential environmental impacts related to landfill leachate are pollution of groundwater and surface waters. Landfill leachate contains pollutants that can be categorized into four groups (dissolved organic matter, inorganic macrocomponents, heavy metals, and xenobiotic organic compounds). Existing data show high leachate concentrations of all components in the early acid phase due to strong decomposition and leaching. In the long methanogenic phase a more stable leachate, with lower concentrations and a low BOD/COD-ratio, is observed. Generally, very low concentrations of heavy metals are observed. In contrast, the concentration of ammonia does not decrease, and often constitutes a major long-term pollutant in leachate. A broad range of xenobiotic organic compounds is observed in landfill leachate. The long-term behavior of landfills with respect to changes in oxidation-reduction status is discussed based on theory and model simulations. It seems that the somewhere postulated enhanced release of accumulated heavy metals would not take place within the time frames of thousands of years. This is supported by a few laboratory investigations. The existing data and model evaluations indicate that the xenobiotic organic compounds in most cases do not constitute a major long-term problem. This may suggest that ammonia will be of most concern in the long run.
Plastics are the most abundant form of marine debris, with global production rising and documented impacts in some marine environments, but the influence of plastic on open ocean ecosystems is poorly understood, particularly for microbial communities. Plastic Marine Debris (PMD) collected at multiple locations in the North Atlantic was analyzed with Scanning Electron Microscopy (SEM) and next-generation sequencing to characterize the attached microbial communities. We unveiled a diverse microbial community of heterotrophs, autotrophs, predators, and symbionts, a community we refer to as the "Plastisphere." Pits visualized in the PMD surface conformed to bacterial shapes as suggesting active hydrolysis of the hydrocarbon polymer. Small-subunit ribosomal RNA gene surveys identified several hydrocarbon-degrading bacteria, supporting the possibility that microbes play a role in degrading PMD. Some Plastisphere members may be opportunistic pathogens such as specific members of the genus Vibrio that dominated one of our plastic samples (the authors, unpublished data). Plastisphere communities are distinct from surrounding surface water, implying that plastic serves as a novel ecological habitat in the open ocean. Plastic has a longer half-life than most natural floating marine substrates, and a hydrophobic surface that promotes microbial colonization and biofilm formation, differing from autochthonous substrates in the upper layers of the ocean.
SILVA (from Latin silva, forest, http://www.arb-silva.de) is a comprehensive web resource for up to date, quality-controlled databases of aligned ribosomal RNA (rRNA) gene sequences
from the Bacteria, Archaea and Eukaryota domains and supplementary online services. The referred database release 111 (July 2012) contains 3 194 778 small subunit
and 288 717 large subunit rRNA gene sequences. Since the initial description of the project, substantial new features have
been introduced, including advanced quality control procedures, an improved rRNA gene aligner, online tools for probe and
primer evaluation and optimized browsing, searching and downloading on the website. Furthermore, the extensively curated SILVA
taxonomy and the new non-redundant SILVA datasets provide an ideal reference for high-throughput classification of data from
next-generation sequencing approaches.
Antibiotic resistance is a worldwide public health concern. Conjugative transfer between closely related strains or species of bacteria is an important method for the horizontal transfer of multidrug-resistance genes. The extent to which nanomaterials are able to cause an increase in antibiotic resistance by the regulation of the conjugative transfer of antibiotic-resistance genes in bacteria, especially across genera, is still unknown. Here we show that nanomaterials in water can significantly promote the horizontal conjugative transfer of multidrug-resistance genes mediated by the RP4, RK2, and pCF10 plasmids. Nanoalumina can promote the conjugative transfer of the RP4 plasmid from Escherichia coli to Salmonella spp. by up to 200-fold compared with untreated cells. We also explored the mechanisms behind this phenomenon and demonstrate that nanoalumina is able to induce oxidative stress, damage bacterial cell membranes, enhance the expression of mating pair formation genes and DNA transfer and replication genes, and depress the expression of global regulatory genes that regulate the conjugative transfer of RP4. These findings are important in assessing the risk of nanomaterials to the environment, particularly from water and wastewater treatment systems, and in the estimation of the effect of manufacture and use of nanomaterials on the environment.
Gephi is an open source software for graph and network analysis. It uses a 3D render engine to display large networks in real-time and to speed up the exploration. A flexible and multi-task architecture brings new possibilities to work with complex data sets and produce valuable visual results. We present several key features of Gephi in the context of interactive exploration and interpretation of networks. It provides easy and broad access to network data and allows for spatializing, filtering, navigating, manipulating and clustering. Finally, by presenting dynamic features of Gephi, we highlight key aspects of dynamic network visualization.
Horizontal gene transfer (HGT) plays an important role in the evolution of life on the Earth. This view is supported by numerous occasions of HGT that are recorded in the genomes of all three domains of living organisms. HGT-mediated rapid evolution is especially noticeable among the Bacteria, which demonstrate formidable adaptability in the face of recent environmental changes imposed by human activities, such as the use of antibiotics, industrial contamination, and intensive agriculture. At the heart of the HGT-driven bacterial evolution and adaptation are highly sophisticated natural genetic engineering tools in the form of a variety of mobile genetic elements (MGEs). The main aim of this review is to give a brief account of the occurrence and diversity of MGEs in natural ecosystems and of the environmental factors that may affect MGE-mediated HGT.
The impact of human activity on the selection for antibiotic resistance in the environment is largely unknown, although considerable amounts of antibiotics are introduced through domestic wastewater and farm animal waste. Selection for resistance may occur by exposure to antibiotic residues or by co-selection for mobile genetic elements (MGEs) which carry genes of varying activity. Class 1 integrons are genetic elements that carry antibiotic and quaternary ammonium compound (QAC) resistance genes that confer resistance to detergents and biocides. This study aimed to investigate the prevalence and diversity of class 1 integron and integron-associated QAC resistance genes in bacteria associated with industrial waste, sewage sludge and pig slurry. We show that prevalence of class 1 integrons is higher in bacteria exposed to detergents and/or antibiotic residues, specifically in sewage sludge and pig slurry compared with agricultural soils to which these waste products are amended. We also show that QAC resistance genes are more prevalent in the presence of detergents. Studies of class 1 integron prevalence in sewage sludge amended soil showed measurable differences compared with controls. Insertion sequence elements were discovered in integrons from QAC contaminated sediment, acting as powerful promoters likely to upregulate cassette gene expression. On the basis of this data, >1 × 10(19) bacteria carrying class 1 integrons enter the United Kingdom environment by disposal of sewage sludge each year.
Microplastics have been found to be ubiquitous in freshwater ecosystems, providing a novel substrate for biofilm formation. Here, we incubated biofilm on microplastics and two natural substrates (rock and leaf) under a controlled environment to investigate the differences of microbial community structure, antibiotic resistance gene (ARG) profiles, and ARG microbial hosts between biofilms on three types of substrates. Results from high-throughput sequencing of 16S rRNA gene revealed that microplastic biofilm had a distinctive community structure. Network analyses suggested that microplastic biofilm possessed the highest node connected community, but with lower average path length, network diameter and modularity compared with biofilm on two natural particles. Metagenomic analyses further revealed microplastic biofilm with broad-spectrum and distinctive resistome. Specifically, according to taxonomic annotation of ARG microbial hosts, two opportunisitic human pathogens (Pseudomonas monteilii, Pseudomonas mendocina) and one plant pathogen (Pseudomonas syringae) were detected only in the microplastic biofilm, but not in biofilms formed on natural substrates. Our findings suggest that microplastic is a novel microbial niche and may serve as a vector for ARGs and pathogens to new environment in river water, generating freshwater environmental risk and exerting adverse impacts on human health.
Microplastics (MPs) are emerging pollutants that have been extensively detected in marine and terrestrial environments. Landfills are receptacles for cumulative loading of plastic waste derived from industry and households, but data on MPs occurrences in landfill systems are lacking. In the current study, the occurrence, characteristics and distribution patterns of MPs in landfills (including leachate and refuse) of the megacity Shanghai were investigated in accordance with different landfill ages (3-20 years). The results revealed that the average abundances of MPs in leachate and refuse were 8 (±3) items/L and 62 (±23) items/g, respectively. The predominant shapes and polymer types of the detected MPs were fibers and cellophane in leachate, whereas they were fragments and polyethylene in refuse. The patterns of abundance and size distribution of MPs in refuse varied from different landfill age, and different polymer MPs exhibited various occurrence patterns with increasing landfill age. Further spectra analysis suggested the presence of oxidative degradation of polyethylene MPs in the landfill process, especially for the landfill time of more than 20 years, so the fates of MPs in landfills were determined by the increase consumptions of plastics products and the degradation process of MPs in landfills. This study firstly provided a systematic overview of MPs pollution characteristics in landfill systems, and the results will foster the understanding of MPs fates over a long time scale in the environments.
The retention of polyvinyl chloride (PVC) microplastics in sewage sludge during wastewater treatment raises concerns. However, the effects of PVC microplastics on methane production from anaerobic digestion of waste activated sludge (WAS) have never been documented. In this work, the effects of PVC microplastics (1 mm, 10-60 particles/g TS) on anaerobic methane production from WAS were investigated. The presence of 10 particles/g TS of PVC microplastics significantly ( P = 0.041) increased methane production by 5.9 ± 0.1%, but higher levels of PVC microplastics (i.e., 20, 40, and 60 particles/g TS) inhibited methane production to 90.6 ± 0.3%, 80.5 ± 0.1%, and 75.8 ± 0.2% of the control, respectively. Model-based analysis indicated that PVC microplastics at >20 particles/g TS decreased both methane potential (B0) and hydrolysis coefficient (k) of WAS. The mechanistic studies showed that bisphenol A (BPA) leaching from PVC microplastics was the primary reason for the decreased methane production, causing significant ( P = 0.037, 0.01, 0.004) inhibitory effects on the hydrolysis-acidification process. The long-term effects of PVC microplastics revealed that the microbial community was shifted in the direction against hydrolysis-acidification and methanation. In conclusion, PVC microplastic caused negative effects on WAS anaerobic digestion through leaching the toxic BPA.
Landfill treatment of municipal solid waste treatment produces a large amount of leachate, which has been an important hotspot of ARGs. This study aimed to investigate the ARGs removal potential, kinetics and mechanism from leachate in aerobic and anaerobic conditions. Simulated landfill reactors showed the efficacy in reducing ARGs, and the removal efficiencies depended on ARGs types and aerobic/anaerobic conditions. The ARGs tetQ and bla CTX-M were more likely to attenuate with the log-removal efficiencies of 1.50–3 order of magnitude. The ARGs removal kinetic was well fitted by modified Collins-Selleck model, and aerobic condition showed better removal capacities and kinetics than anaerobic condition. Among the ARGs with great removal performance, sul2, aadA1and bla CTX-M were eliminated from leachate and refuse simultaneously, but tetM, ermB, and mefA were removed from leachate but enriched in refuse. Aerobic/anaerobic states might drive the bacterial community shift of leachate and refuse, and topology property comparison of co-occurrence networks suggested that refuse had a closer non-random host relationship between ARGs and microbial taxa than leachate. Further module analyses revealed that ARGs removal efficiencies depended on the taxonomy of host bacteria in leachate, while the refuse taxa-ARGs correlation determined ARGs removal patterns. By selecting distinct bacteria cluster in different conditions, aerobic treatment benefited ARGs reduction in leachate and refuse, while anaerobic treatment enhanced the enrichment of ARGs in refuse. These findings can potentially foster the understanding of ARGs removal mechanism in biological treatment processes.
Conditioning can drastically improve the dewaterability of sewage sludge and thus it is widely practiced in most wastewater treatment plants (WWTPs). In WWTPs, various antibiotic resistance genes (ARGs) present in sewage are concentrated in the sewage sludge, but the effect of sludge conditioning on ARGs in sewage sludge remains unclear. Here, we evaluated and compared the effectiveness of four sludge conditioning methods (namely chemical conditioning with polyacrylamide (PAM), chemical conditioning with Fe[III]/CaO, bioleaching conditioning, and chemical acidification conditioning) and an aerobic incubation control in removing 46 target ARGs and intI1 from a municipal sewage sludge. The damage of sludge microbial cells and the change in the sludge bacterial community during the various sludge conditioning treatments were also characterized. The results suggested that the chemical conditioning with PAM and aerobic incubation treatment did not remove ARGs and intI1 from the sewage sludge. The chemical acidification reduced the absolute abundances of most ARGs and intI1, but increased their relative abundances. However, the chemical conditioning with Fe[III]/CaO and bioleaching conditioning reduced both the absolute and relative abundances of most ARGs and removed a majority of extracellular ARGs in the sludge. During sludge conditioning treatments, the sludge microbial cells were severely damaged to decrease the total bacterial biomass in sludge, and accordingly the bacterial hosts carrying ARGs and intI were effectively damaged to reduce the absolute abundances of most ARGs and intI1. In addition, the sludge bacterial community in conditioned sludge determined the relative abundances of residual ARGs. Our findings suggest that sludge conditioning can be an important sludge treatment process in attenuating antibiotic resistance in sewage sludge, and bioleaching and chemical conditioning with Fe[III]/CaO can be employed as effective conditioning ways to reduce ARGs in sewage sludge, potentially limiting their release to the environment.
Increased utilization of titanium dioxide nanoparticles (TiO2 NPs) for commercial as well as industrial purposes resulted in the accumulation of nanoparticles in the marine system. Microplastics being an emerging secondary pollutant in the marine ecosystem have an impact on the toxic effects of TiO2 NPs which has not been evaluated up to date. So it is important to assess the toxic effects of both these pollutants on the marine environment. The present study examines the impact of differently functionalized microplastics on the toxic effects of P25 TiO2 NPs to marine algae Chlorella sp. The tendency of nanoparticles to undergo aggregation in artificial seawater was observed with increase in time. The median effective concentration for TiO2 NPs was found to be 81 μM which indicates higher toxic effects of NPs toward algae. In contrast, microplastics irrespective of their difference in functionalization had minimal toxic effect of about 15% at their higher concentration tested, 1000 mg L⁻¹. Plain and aminated polystyrene microplastics enhanced the TiO2 NPs toxicity which was further validated with oxidative stress determination studies like reactive oxygen species and lipid peroxidation assays. Negatively charged carboxylated polystyrene microplastics decreased the TiO2 NPs toxicity with possible hetero-aggregation between TiO2 NPs and microplastics in the system. The toxicity data obtained for the mixture was further corroborated with Abbott's mathematical model.
Emerging contaminants, such as engineered metal oxides nanoparticles (NPs) and antibiotic resistance genes (ARGs), were reported to be accumulated in waste activated sludge. In this study, the potential impacts of CuO and ZnO NPs on the fate of ARGs during sludge anaerobic digestion were assessed. Metagenomic results showed that the presence of CuO or ZnO NPs increased ARGs abundances but had no significant effects on the percentages of resistance mechanisms and types. Further functional analysis of the metagenomes revealed that signal transduction were stimulated by both NPs, especially two-component regulatory systems (TCRS) responsible for quorum sensing (QS), pili synthesis and metal tolerance. Moreover, it was found that the activated QS was closely associated with the shifted bacterial communities, especially the enriched genera, such as Acidovorax, Burkholderia, Pseudomonas and Rhodobacter, which were not only the producers of QS signals but also the hosts of ARGs. Meanwhile, the triggered pili synthesis, combining with the increased abundances of mobile genetic elements (plasmids, integrons and insertion sequences), would facilitate the transfer of ARGs among diverse bacteria. Furthermore, the induced resistance to copper/zinc and other metal, such as mercury and arsenic, probably promoted the co-selection between metal and antibiotic resistance. The above results indicated that the propagation of ARGs in digesters might be driven by the NPs-stimulated signal transduction. These findings may bring new insights to the understanding of ARGs responses to diverse environmental stimuli.
(Nano)microplastics (N/MPs) are emerging contaminants of increasing concerns. However, little is known about the potential toxicity difference between nanoplastics and microplastics on organisms. In this study, we investigated the effects of polystyrene N/MPs with diameter sizes of 100 and 500 nm in nanoscale and 1.0, 2.0 and 5.0 μm in microscale on survival, lifespans, motor behaviors, movement-related neurons and oxidative stress in Caenorhabditis elegans. After 3 days exposure to 1.0 mg L-1 polystyrene particles with five sizes, 1.0 μm group resulted in the lowest survival rate, the largest decrease in body length and the shortest average lifespan in nematodes. We demonstrated that N/MPs exposure accelerated frequency in body bending and head thrashing, and increased crawling speed, which indicates that N/MPs can induce size-dependent excitatory toxicity on locomotor behaviors. Of five sizes of N/MPs, 1.0 μm particles significantly down-regulated the expression of unc-17 and unc-47, and resulted in obvious damages in cholinergic and GABAergic neurons. We also found that polystyrene N/MPs significantly elevated the expression of gst-4, which encodes Glutathione S-transferase-4, a key enzyme in oxidative stress. Additionally, N/MPs-induced oxidative damages were effectively attenuated by natural antioxidants, curcumin and oligometric proanthocyanidins. Taken together, these findings suggest that (nano)microplastics can exert size-dependent toxicity and have extensive impacts on organisms.
Nano- and microplastics have been shown to cause negative effects on marine organisms. However, the toxicities of nano- and microplastics toward marine bacteria are poorly understood. In this study, we investigated the toxic effects of polystyrene nano- and microplastics on the marine bacterium Halomonas alkaliphila by determining growth inhibition, chemical composition, inorganic nitrogen conversion efficiencies and reactive oxygen species (ROS) generation. The results showed that both nano- and microplastics inhibited the growth of H. alkaliphila in high concentrations, while nanoplastics rather than microplastics influenced the growth inhibition, chemical composition and ammonia conversion efficiencies of H. alkaliphila at concentration of 80 mg/L. The ROS generation indicated oxidative stress induced by nano- but not microplastics, and the oxidative stress induced by nanoplastics may provide a significant effect on bacteria. Furthermore, the positively charged nanoplastics (amine-modified 50 nm) induced higher oxidative stress toward bacteria than that induced by negatively charged nanoplastics (non-modified 55 nm). The increased extracellular polymeric substances as evidenced by transmission electron microscope (TEM) observation suggested the possible bacterial protective mechanisms. The present study illustrates for the first time the impact of plastics debris on the inorganic nitrogen conversion efficiencies of marine bacteria. Our findings highlight the effects of microplastics on the ecological function of marine organisms.
Microplastics are ubiquitous not just in the ocean but also on land and in freshwater systems
High throughput sequencing-based metagenomic analysis and network analysis were applied to investigate the broad-spectrum profiles of ARGs in landfill leachate from 12 cities in China. In total, 526 ARG subtypes belonging to 21 ARG types were detected with abundances ranging from 1.1 × 10-6 to 2.09 × 10-1 copy of ARG/copy of 16S rRNA gene. 68 ARG subtypes that accounted for 73.4%-93.4% of the total ARG abundances were shared by all leachate samples. The four most abundant ARGs, sul1, sul2, aadA and bacA can be served as ARG indicators to quantitatively predict the total abundances by linear functions (r2 = 0.577-0.819, P < 0.001). No distinct regional distribution pattern of the ARGs was observed among different cities in China, while the ARG compositions of the leachate were clearly distinct from those of other environmental sample types. Nearly 90% ARG subtypes in the anaerobic digestion sludge from sewage treatment plants (STPADS) were shared by the leachate and the abundances of leachate and STPADS ARGs generalists accounted for 84.5% and 87.7% of total abundances in these two types of anaerobic samples, respectively. Furthermore, Procrustes analysis suggested that microbial community composition might be the determining factor of ARG compositions in landfill leachate. ARGs within the same type or among the different types showed higher incidences of non-random co-occurrence and 17 genera might be potential hosts of multiple ARGs. This study highlighted that landfill leachate is an important reservoir of various ARGs and provided a useful reference for the surveillance and risk management of ARGs in landfill environments.
Plastic pollution is a major global concern with several million microplastic particles entering every day freshwater ecosystems via wastewater discharge. Microplastic particles stimulate biofilm formation (plastisphere) throughout the water column and have the potential to affect microbial community structure if they accumulate in pelagic waters, especially enhancing the proliferation of biohazardous bacteria. To test this scenario, we simulated the inflow of treated wastewater into a temperate lake using a continuous culture system with a gradient of concentration of microplastic particles. We followed the effect of microplastics on the microbial community structure and on the occurrence of integrase 1 (int1), a marker associated with mobile genetic elements known as a proxy for anthropogenic effects on the spread of antimicrobial resistance genes. The abundance of int1 increased in the plastisphere with increasing microplastic particle concentration, but not in the water surrounding the microplastic particles. Likewise, the microbial community on microplastic was more similar to the original wastewater community with increasing microplastic concentrations. Our results show that microplastic particles indeed promote persistence of typical indicators of microbial anthropogenic pollution in natural waters, and substantiate that their removal from treated wastewater should be prioritised.
Plastics can be found in all ecosystems across the globe. This type of environmental pollution is important, even if its impact is not fully understood. The presence of small plastic particles at the micro- and nanoscales is of growing concern, but nanoplastic has not yet been observed in natural samples. In this study, we examined four size fractions (meso-, large micro-, small micro-, and nanoplastics) of debris collected in the North Atlantic subtropical gyre. To obtain the nanoplastic portion, we isolated the colloidal fraction of seawater. After ultrafiltration, the occurrence of nanoscale particles was demonstrated using dynamic light scattering experiments. The chemical fingerprint of the colloids was obtained by pyrolysis coupled with gas chromatography–mass spectrometry. We demonstrated that the signal was anthropogenic and attributed to a combination of plastics. The polymer composition varied among the size classes. At the micro- and nanoscales, polyvinyl chloride, polyethylene terephthalate, polystyrene and polyethylene were observed. We also observed changes in the pyrolytic signals of polyethylene with decreasing debris size, which could be related to the structural modification of this plastic as a consequence of weathering.
Landfills receive about 350 million tons of municipal solid wastes (MSWs) per year globally, including antibiotics and other co-selecting agents that impact antimicrobial resistance (AMR). However, little is known about AMR in landfills, especially as a function of landfill ages. Here we quantified antibiotics, heavy metals, and AMR genes (ARGs) in refuse and leachates from landfills of different age (< 3, 10, and > 20 years). Antibiotics levels were consistently lower in refuse and leachates from older landfills, whereas ARG levels in leachates significantly increased with landfill age (One-way ANOVA, F = 10.8, P < 0.01). Heavy metals whose contents increased as landfills age (One-way ANOVA, F = 12.3, P < 0.01) were significantly correlated with elevated levels of ARGs (Mantel test, R = 0.66, P < 0.01) in leachates, which implies greater AMR exposure risks around older landfills. To further explain ARGs distributional mechanisms with age, microbial communities, mobile genetic elements (MGEs) and environmental factors were contrasted between refuse and leachate samples. Microbial communities in the refuse were closely correlated with ARG contents (Procrustes test; M2 = 0.37, R = 0.86, P < 0.001), whereas ARG in leachates were more associated with MGEs.
Landfills are so far the most common practice for the disposals of municipal solid waste (MSW) worldwide. Since MSW landfill receives miscellaneous wastes, including unused/expired antibiotics and bioactive wastes, it gradually becomes a huge potential bioreactor for breeding antibiotic resistance. Antibiotic resistance genes (ARGs) in landfill can flow to the environment through leakage of landfill leachate and pose a risk to public health. Using high throughput quantitative Polymerase Chain Reaction (HT-qPCR), we investigated the prevalence, diversity of ARGs and its association with various mobile genetic elements (MGEs) in MSW landfill groundwater. Totally 171 unique ARGs (belonging to 9 ARG types, encompassing 3 major resistance mechanisms) and 8 MGEs (6 transposase genes, and 2 integron-integrase genes) were identified. The normalized abundance of ARG was ranging from 0.24 to 5.66 copies/cell with multidrug, beta-lactams and tetracycline resistance genes being the most abundant ARG types. The co-occurrence pattern and significant correlation between MGEs and ARGs, indicated that MGEs may play an important role in the persistence and proliferation of ARGs. A Mantel test and Procrustes analysis suggested that ARG profiles were significantly correlated with bacterial community. Variation partitioning analysis (VPA) further demonstrated that bacterial community shifts contribute 65.8% of the total ARG variations. Additionally network analysis revealed that 15 bacterial taxa at family level might be the potential hosts of ARGs. These findings provide evidence that groundwater near MSW landfill is an underappreciated hotspot of antibiotic resistance and contribute to the spread of ARGs via the flowing contaminated groundwater.
This review article summarises the sources, occurrence, fate and effects of plastic waste in the marine environment. Due to its resistance to degradation, most plastic debris will persist in the environment for centuries and may be transported far from its source, including great distances out to sea. Land- and ocean-based sources are the major sources of plastic entering the environment, with domestic, industrial and fishing activities being the most important contributors. Ocean gyres are particular hotspots of plastic waste accumulation. Both macroplastics and microplastics pose a risk to organisms in the natural environment, for example, through ingestion or entanglement in the plastic. Many studies have investigated the potential uptake of hydrophobic contaminants, which can then bioaccumulate in the food chain, from plastic waste by organisms. To address the issue of plastic pollution in the marine environment, governments should first play an active role in addressing the issue of plastic waste by introducing legislation to control the sources of plastic debris and the use of plastic additives. In addition, plastics industries should take responsibility for the end-of-life of their products by introducing plastic recycling or upgrading programmes.
We present the open-source software package DADA2 for modeling and correcting Illumina-sequenced amplicon errors (https://github.com/benjjneb/dada2). DADA2 infers sample sequences exactly and resolves differences of as little as 1 nucleotide. In several mock communities, DADA2 identified more real variants and output fewer spurious sequences than other methods. We applied DADA2 to vaginal samples from a cohort of pregnant women, revealing a diversity of previously undetected Lactobacillus crispatus variants.
There has been a considerable increase on research of the ecological consequences of microplastics released into the environment, but only a handful of works have focused on the nano-sized particles of polymer-based materials. Though their presence has been difficult to adequately ascertain, due to the inherent technical difficulties for isolating and quantifying them, there is an overall consensus that these are not only present in the environment – either directly released or as the result of weathering of larger fragments – but that they also pose a significant threat to the environment and human health, as well. The reduced size of these particulates (< 1 μm) makes them susceptible of ingestion by organisms that are at the base of the food-chain. Moreover, the characteristic high surface area-to-volume ratio of nanoparticles may add to their potential hazardous effects, as other contaminants, such as persistent organic pollutants, could be adsorbed and undergo bioaccumulation and bioamplification phenomena.
The generation and seasonal variations of secondary pollutants were investigated during three municipal solid waste (MSW) compression and transfer in Shanghai, China. The results showed that the raw wastewater generated from three MSW transfer stations had pH of 4.2-6.0, COD 40,000-70,000mg/L, BOD5 15,000-25,000mg/L, ammonia nitrogen (NH3-N) 400-700mg/L, total nitrogen (TN) 600-1500mg/L, total phosphorus (TP) 50-200mg/L and suspended solids (SS) 1000-80,000mg/L. The pH, COD, BOD5 and NH3-N did not show regular change throughout the year while the concentration of TN, TP and SS were higher in summer and autumn. The animal and vegetable oil content was extremely high. The average produced raw wastewater of three transfer stations ranged from 2.3% to 8.4% of total refuse. The major air pollutants of H2S 0.01-0.17mg/m(3), NH3 0.75-1.8mg/m(3) in transfer stations, however, the regular seasonal change was not discovered. During the transfer process, the generated leachate in container had pH of 5.7-6.4, SS of 9120-32,475mg/L. The COD and BOD5 were 41,633-89,060mg/L and 18,116-34,130mg/L respectively, higher than that in the compress process. The concentration of NH3-N and TP were 587-1422mg/L and 80-216mg/L, respectively, and both increased during transfer process. H2S, VOC, CH4 and NH3 were 0.4-4mg/m(3), 7-19mg/m(3), 0-3.4% and 1-4mg/m(3), respectively. The PCA analysis showed that the production of secondary pollutants is closely related to temperature, especially CH4. Therefore, avoiding high temperature is a key means of reducing the production of gaseous pollutants. And above all else, refuse classification in source, deodorization and anti-acid corrosion are the important processes to control the secondary pollutants during compression and transfer of MSW.
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