Bacterial Community under the Influence of Microplastics in Indoor Environment and the Health Hazards Associated with Antibiotic Resistance Genes

Microplastic generation from field-collected plastic gauze: Unveiling the aging processes

Accumulation of plastic debris in the environment is a matter of global concern. As plastic ages, it generates microplastic (MP) particles with high mobility. Understanding how MPs are generated is crucial to controlling this emerging contaminant. In this study, we utilized high-density polyethylene (HDPE) plastic gauze, collected from urban settings, as a representative example of plastic waste. The plastic gauze was subjected to various aging conditions, including freeze-thaw cycling, mechanical abrasion, and UV irradiation. Following aging, the plastic gauze was rinsed with water, and the number of generated MPs were quantified. It was found that aged plastic gauze generated up to 334 million MP particles per m2 (> 10 µm) during rinsing, a number two orders of magnitude higher than unaged plastic. Fragmentation occurred in two dimensions for bulk MPs of all morphotypes. However, specific aging approaches (i.e., mechanical abrasion and UV irradiation) generated spheres and fibers via pseudo-3D fragmentation. Additionally, changes in molecular weight, size distribution, and surface oxidation characteristics unveiled a complex pattern (i.e., irregular changes with exposure time). This complexity underscores the intricate nature of plastic debris aging processes in the environment.

Impacts of polypropylene microplastics on the distribution of cadmium, enzyme activities, and bacterial community in black soil at the aggregate level

Microplastics (MPs) can co-occur widely with heavy metals in soil. This study intended to investigate the influences of the co-exposure of polyethylene MPs (0.5 %, w/w) and cadmium (Cd) in black soil on the Cd distribution, enzyme activities, and bacterial communities in both bulk soil and different sized soil aggregates (> 1, 0.50-1, 0.25-0.50, and < 0.25 mm aggregates) after a 90-day incubation. Our results showed that the existence of MPs increased the distributions of Cd in >1 mm and < 0.25 mm soil aggregates and decreased its distributions in 0.50-1 mm and 0.25-0.50 mm soil aggregates. About 12.15 %-17.65 % and 9.03 %-11.13 % of Cd were distributed in the exchangeable and oxidizable forms in bulk soil and various sized soil aggregates after the addition of MPs which were higher than those in the only Cd-treated soil (11.17 %-14.72 % and 8.66 %-10.43 %, respectively), while opposite tendency was found for Cd in the reducible form. Urease and β-glucosidase activities in the Cd-treated soils were 1.14-1.18 and 1.07-1.31 times higher than those in the Cd-MPs treated soils. MPs disturbed soil bacterial community at phylum level and increased the bacteria richness in bulk soil. The levels of predicted functional genes which are linked to the biodegradation and metabolism of exogenous substances and soil C and N cycles were altered by the co-exposure of Cd and MPs. The findings of this study could help deepen our knowledge about the responses of soil properties, especially microbial community, to the co-occurrence of MPs and heavy metals in soil.

Quantification and Characterization of Fine Plastic Particles as Considerable Components in Atmospheric Fine Particles

The negative effects of air pollution, especially fine particulate matter (PM2.5, particles with an aerodynamic diameter of ≤2.5 μm), on human health, climate, and ecosystems are causing significant concern. Nevertheless, little is known about the contributions of emerging pollutants such as plastic particles to PM2.5 due to the lack of continuous measurements and characterization methods for atmospheric plastic particles. Here, we investigated the levels of fine plastic particles (FPPs) in PM2.5 collected in urban Shanghai at a 2 h resolution by using a novel versatile aerosol concentration enrichment system that concentrates ambient aerosols up to 10-fold. The FPPs were analyzed offline using the combination of spectroscopic and microscopic techniques that distinguished FPPs from other carbon-containing particles. The average FPP concentrations of 5.6 μg/m3 were observed, and the ratio of FPPs to PM2.5 was 13.2% in this study. The FPP sources were closely related to anthropogenic activities, which pose a potential threat to ecosystems and human health. Given the dramatic increase in plastic production over the past 70 years, this study calls for better quantification and control of FPP pollution in the atmosphere.

Potential environmental risks of field bio/non-degradable microplastic from mulching residues in farmland: Evidence from metagenomic analysis of plastisphere

The plastisphere may act as reservoir of antibiotic resistome, accelerating global antimicrobial resistance dissemination. However, the environmental risks in the plastisphere of field microplastics (MPs) in farmland remain largely unknown. Here, antibiotic resistance genes (ARGs) and virulence factors (VFs) on polyethylene microplastics (PE-MPs) and polybutylene adipate terephthalate and polylactic acid microplastics (PBAT/PLA-MPs) from residues were investigated using metagenomic analysis. The results suggested that the profiles of ARG and VF in the plastisphere of PBAT/PLA-MPs had greater number of detected genes with statistically higher values of diversity and abundance than soil and PE-MP. Procrustes analysis indicated a good fitting correlation between ARG/VF profiles and bacterial community composition. Actinobacteria was the major host for tetracycline and glycopeptide resistance genes in the soil and PE-MP plastisphere, whereas the primary host for multidrug resistance genes changed to Proteobacteria in PBAT/PLA-MP plastisphere. Besides, three human pathogens, Sphingomonas paucimobilis, Lactobacillus plantarum and Pseudomonas aeruginosa were identified in the plastisphere. The PE-MP plastisphere exhibited a higher transfer potential of ARGs than PBAT/PLA-MP plastisphere. This work enhances our knowledge of potential environmental risks posed by microplastic in farmland and provides valuable insights for risk assessment and management of agricultural mulching applications.

Underestimated activity-based microplastic intake under scenario-specific exposures

Despite increasing alarms over the health impacts of microplastics (MPs) due to their detection in human organs and feces, precise exposure evaluations remain scarce. To comprehend their risks, there is a distinct need to prioritize quantitive estimates in MP exposome, particularly at the environmentally-realistic level. Here we used a method rooted in real-world MP measurements and activity patterns to determine the daily intake of MPs through inhalation and from ground dust/soil ingestion. We found that nearly 80% of this intake comes from residential sectors, with activity intensity and behavioral types significantly affecting the human MP burden. The data showed a peak in MP exposure for those aged 18-64. When compared to dietary MP intake sources like seafood, salt, and water, we identified a previously underestimated exposure from inhalation and dust/soil ingestion, emphasizing the need for more realistic evaluations that incorporate activity factors. This discovery raises questions about the accuracy of past studies and underscores MP's potential health risks. Moreover, our time-based simulations revealed increased MP intake during the COVID-19 lockdown due to more surface dust ingestion, shedding light on how global health crises may inadvertently elevate MP exposure risks.

Chronic exposure to low concentrations of microplastics causing gut tissue damage but non-significant changes in the microbiota of marine medaka larvae (Oryzias melastigma)

Microplastics (MPs) have become a popular research topic due to their potential ramifications on aquatic organisms. To evaluate the ecotoxicological impacts of chronic exposure to different microplastics on marine medaka larvae, we exposed medaka larvae to 200 μg/L of polyethylene (PE-200) and polylactic acid (PLA-200) microplastics for 60 days, respectively. The results indicated that both exposures had no significant effect on fish length/weight and did not result in fish mortality. Notably, the structure of intestinal microbiota was not disrupted either. However, microscopy observations of intestinal tissue suggested that exposure to MPs resulted in inflammation of the intestinal tract of fish and significant atrophy and shedding of small intestinal villus. Linear discriminant analysis Effect Size (LEfSe) showed that intestinal enrichment of Streptomyces occurred in marine medaka larvae in both MPs treatments, while the PE-200 treatment exhibited a significant enrichment. In addition, the PICRUSt2 prediction indicated significant upregulation of the Novobiocin biosynthesis function in gut microbiota in the PE-200 treatment. Overall, multi-level assessment is necessary to determine the risk of exposure of aquatic organisms to MPs.

Human Exposure to Ambient Atmospheric Microplastics in a Megacity: Spatiotemporal Variation and Associated Microorganism-Related Health Risk

Microplastics are found in various human tissues and are considered harmful, raising concerns about human exposure to microplastics in the environment. Existing research has analyzed indoor and occupational scenarios, but long-term monitoring of ambient atmospheric microplastics (AMPs), especially in highly polluted urban regions, needs to be further investigated. This study estimated human environmental exposure to AMPs by considering inhalation, dust ingestion, and dermal exposure in three urban functional zones within a megacity. The annual exposure quantity was 7.37 × 104 items for children and 1.06 × 105 items for adults, comparable with the human microplastic consumption from food and water. Significant spatiotemporal differences were observed in the characteristics of AMPs that humans were exposed to, with wind speed and rainfall frequency mainly driving these changes. The annual human AMP exposure quantity in urban green land spaces, which were recognized as relatively low polluted zones, was comparable with that in public service zones and residential zones. Notably, significant positive correlations between the AMP characteristics and the pathogenicity of the airborne bacterial community were discovered. AMP size and immune-mediated disease risks brought by atmospheric microbes showed the most significant relationship, where Sphingomonas might act as the potential key mediator.

Heterogeneous Photodegradation Behavior of Liquid Crystal Monomers in Dust: Quantitative Structure-Activity Relationship and Product Identification

The heterogeneous photodegradation behavior of liquid crystal monomers (LCMs) in standard dust (standard reference material, SRM 2583) and environmental dust was investigated. The measured photodegradation ratios for 23 LCMs in SRM and environmental dust in 12 h were 11.1 ± 1.8 to 23.2 ± 1.1% and 8.7 ± 0.5 to 24.0 ± 2.8%, respectively. The degradation behavior of different LCM compounds varied depending on their structural properties. A quantitative structure-activity relationship model for predicting the degradation ratio of LCMs in SRM dust was established, which revealed that the molecular descriptors related to molecular polarizability, electronegativity, and molecular mass were closely associated with LCMs' photodegradation. The photodegradation products of the LCM compound 4'-propoxy-4-biphenylcarbonitrile (PBIPHCN) in dust, including •OH oxidation, C-O bond cleavage, and ring-opening products, were identified by nontarget analysis, and the corresponding degradation pathways were suggested. Some of the identified products, such as 4'-hydroxyethoxy-4-biphenylcarbonitrile, showed predicted toxicity (with an oral rat lethal dose of 50%) comparable to that of PBIPHCN. The half-lives of the studied LCMs in SRM dust were estimated at 32.2-82.5 h by fitting an exponential decay curve to the observed photodegradation data. The photodegradation mechanisms of LCMs in dust were revealed for the first time, enhancing the understanding of LCMs' environmental behavior and risks.

Microplastisphere antibiotic resistance genes: A bird's-eye view on the plastic-specific diversity and enrichment

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.

Dynamic evolution of antibiotic resistance genes in plastisphere in the vertical profile of urban rivers

Microplastics (MPs) can vertically transport in the aquatic environment due to their aging and biofouling, forming distinct plastisphere in different water layers. However, even though MPs have been regarded as hotspots for antibiotic resistance genes (ARGs), little is known about the propagation and transfer of ARGs in plastisphere in waters, especially in the vertical profile. Therefore, this study investigated the dynamic responses and evolution of ARGs in different plastisphere distributed vertically in an urbanized river. The biofilm biomass in the polylactic acid (PLA) plastisphere was relatively higher than that in the polyethylene terephthalate (PET), showing depth-decay variations. The ARGs abundance in plastisphere were much higher than that in the surrounding waters, especially for the PLA. In the vertical profiles, the ARGs abundance in the PET plastisphere increased with water depths, while the highest abundance of ARGs in the PLA mostly appeared at intermediate waters. In the temporal dynamic, the ARGs abundance in plastisphere increased and then decreased, which may be dominated by the MP types at the initial periods. After long-term exposure, the influences of water depths seemed to be strengthened, especially in the PET plastisphere. Compared with surface waters, the microbiota attached in plastisphere in deep waters showed high species richness, strong diversity, and complex interactions, which was basically consistent with the changes of nutrient contents in different water layers. These vertical variations in microbiota and nutrients (e.g., nitrogen) may be responsible for the propagation of ARGs in plastisphere in deep waters. The host bacteria for ARGs in plastisphere was also developed as water depth increased, leading to an enrichment of ARGs in deep waters. In addition, the abundance of ARGs in plastisphere in bottom waters was positively correlated with the mobile genetic elements (MGEs) of intI1 and tnpA05, indicative of a frequent horizontal gene transfer of ARGs. Overall, water depth played a critical role in the propagation of ARGs in plastisphere, which should not be ignored in a long time series. This study provides new insights into the dynamic evolution of ARGs propagation in plastisphere under increasing global MPs pollution, especially in the vertical profile.

Pollution characteristics and potential health effects of airborne microplastics and culturable microorganisms during urban haze in Harbin, China

In this study, active sampling technology was used to collect microplastics (MPs) and microorganisms simultaneously on haze days in Harbin, China. Airborne MPs concentrations in Junior high school (162.4 ± 44.6 particles/m3) with high vehicular and pedestrian traffic was higher than those in University (63.2 ± 21.8 particles/m3) and Park (12.8 ± 5.5 particles/m3). More airborne MPs were detected in the night samples than in the morning and noon samples. The majority (69.06 %) of airborne MPs measured less than 100 μm, with fibers (69.4 %) being the predominant form. Polyesters and polyethylene were the dominant polymers. In addition, airborne MPs concentrations were positively correlated with microorganisms and PM10 concentrations, and the health hazards associated with microorganisms and MPs exposure via inhalation far exceeded those associated with skin contact, which can serve as a theoretical foundation for considering MPs as indicators of air quality in the future.

Microplastics in the atmosphere: Adsorb on leaves and their effects on the phyllosphere bacterial community

Phyllosphere is the largest interface between the atmosphere and terrestrial ecosystems and serves as a major sink for atmospheric microplastics (MPs). It is also a unique habitat for microbiota with diverse ecological functions. This field study investigated the characteristics of atmospheric MPs adsorbed on leaves with automatic technology, and found their abundance was 3.62 ± 1.29 items cm-2. MPs on leaves were mainly below 80 µm, and dominated by polyamide, polyethene, and rubber. MPs on leaves correlated significantly with the structure and functions of the phyllosphere bacterial community (PBC). Both the MPs abundance and size distribution (MSD) were positively correlated with the α diversity and negatively correlated with the β diversity and network complexity of PBC. PBC functions of environmental and genetic information process were negatively correlated with MPs abundance, and functions related to human diseases and cellular process were positively correlated with MSD significantly. The relative abundance of Sphingomonas was significantly correlated with the MSD, suggesting that Sphingomonas might emerge as the key genus involved in the pathogenicity of PBC mediated by MPs. These results highlighted the ecological health risks of atmospheric MPs as they can be transferred anywhere and potentially increase the pathogenicity of local phyllosphere microflora.

Distinct spatiotemporal succession of bacterial generalists and specialists in the lacustrine plastisphere

The assembly processes of generalists and specialists and their driving mechanisms during spatiotemporal succession is a central issue in microbial ecology but a poorly researched subject in the plastisphere. We investigated the composition variation, spatiotemporal succession, and assembly processes of bacterial generalists and specialists in the plastisphere, including non-biodegradable (NBMPs) and biodegradable microplastics (BMPs). Although the composition of generalists and specialists on NBMPs differed from that of BMPs, colonization time mainly mediated the composition variation. The relative abundance of generalists and the relative contribution of species replacement were initially increased and then decreased with colonization time, while the specialists initially decreased and then increased. Besides, the richness differences also affected the composition variation of generalists and specialists in the plastisphere, and the generalists were more susceptible to richness differences than corresponding specialists. Furthermore, the assembly of generalists in the plastisphere was dominated by deterministic processes, while stochastic processes dominated the assembly of specialists. The network stability test showed that the community stability of generalists on NBMPs and BMPs was lower than corresponding specialists. Our results suggested that different ecological assembly processes shaped the spatiotemporal succession of bacterial generalists and specialists in the plastisphere, but were less influenced by polymer types.

Research progress on the role of biofilm in heavy metals adsorption-desorption characteristics of microplastics: A review

Microplastics (MPs) have been found to be widely distributed in aquatic environments, where they will interact with toxic heavy metals and result in more serious adverse effects on the aquatic environments and organisms. However, after entering the aquatic environments, MPs are quickly covered by biofilms, which significantly modify MPs properties and relevant heavy metals adsorption-desorption characteristics In order to better understand the adsorption behavior of heavy metals on biofilm developed MPs (BMPs), we comprehensively reviewed representative studies in this area. First, we summarized the formation process of biofilms on MPs. Subsequently, we reviewed the current understanding on the influence of biofilm formation on the properties of MPs and discussed the metal adsorption-desorption characteristics of MPs affected by these changes. Finally, based on the systematic literature review, some future research needs and strategies were proposed to further understand the interactions between MPs and heavy metals.

Plastic substrate and residual time of microplastics in the urban river shape the composition and structure of bacterial communities in plastisphere

The widespread secondary microplastics (MPs) in urban freshwater, originating from plastic wastes, have created a new habitat called plastisphere for microorganisms. The factors influencing the structure and ecological risks of the microbial community within the plastisphere are not yet fully understood. We conducted an in-site incubation experiment in an urban river, using MPs from garbage bags (GB), shopping bags (SB), and plastic bottles (PB). Bacterial communities in water and plastisphere incubated for 2 and 4 weeks were analyzed by 16S high-throughput sequencing. The results showed the bacterial composition of the plastisphere, especially the PB, exhibited enrichment of plastic-degrading and photoautotrophic taxa. Diversity declined in GB and PB but increased in SB plastisphere. Abundance analysis revealed distinct bacterial species that were enriched or depleted in each type of plastisphere. As the succession progressed, the differences in community structure was more pronounced, and the decline in the complexity of bacterial community within each plastisphere suggested increasing specialization. All the plastisphere exhibited elevated pathogenicity at the second or forth week, compared to bacterial communities related to natural particles. These findings highlighted the continually evolving plastisphere in urban rivers was influenced by the plastic substrates, and attention should be paid to fragile plastic wastes due to the rapidly increasing pathogenicity of the bacterial community attached to them.

Development of a solubility parameter calculation-based method as a complementary tool to traditional techniques for indoor dust microplastic determination and risk assessment

Herein, a method based on solubility parameter calculation was first used to analyze microplastics in indoor dust. The limit of quantification (LOQ) reached 0.2 mg/g, and the result of reference material SRM 2585 (n = 3) was 14.8 mg/g ± 1.8 %, suggesting satisfying sensitivity and precision. Recoveries of spiking experiments were > 80 % with no obvious matrix interferences observed, except ethylene propylene diene monomer (EPDM) MPs. Further, 69 indoor dust samples were analyzed to verify the method and to assess exposure scenarios for graduate students in Tianjin, China. EPDM was identified in an indoor environment for the first time as the second most widely detected type after PET in this work. The mass-based result is complementary to the outcomes from thermogravimetric analysis-gas chromatography-mass spectrometry and laser direct infrared imaging. Significant correlations were found between total organic carbon (TOC), microplastics, and BDE-209 concentrations, indicating microplastics important contaminant vectors in indoor dust. Dormitory stays and PET contributed the most to health risks among the three exposure scenarios and detected four polymers, respectively. This work provides an approach with the potential for the standardized determination of microplastics in complex environmental matrices and reveals exposure characteristics of indoor dust microplastics.

Plant biomass mediates the decomposition of polythene film-sourced pollutants in soil through plastisphere bacteria island effect

The polyethylene (PE) film mulching as a water conservation technology has been widely used in dryland agriculture, yet the long-term mulching has led to increasing accumulation of secondary pollutants in soils. The decomposition of PE film-sourced pollutants is directly associated with the enrichment of specific bacterial communities. We therefore hypothesized that plant biomass may act as an organic media to mediate the pollutant decomposition via reshaping bacterial communities. To validate this hypothesis, plant biomass (dried maize straw and living clover) was embedded at the underlying surface of PE film, to track the changes in the composition and function of bacterial communities in maize field across two years. The results indicated that both dry crop straw and alive clover massively promoted the α-diversity and abundance of dominant bacteria at plastisphere, relative to bulk soil. Bacterial communities tended to be clustered at plastisphere, forming the bacteria islands to enrich pollutant-degrading bacteria, such as Sphingobacterium, Arthrobacter and Paracoccus. As such, plastisphere bacteria islands substantially enhanced the degradation potential of chloroalkene and benzoate (p < 0.05). Simultaneously, bacterial network became stabilized and congregated at plastisphere, and markedly improved the abundance of plastisphere module hubs and connectors bacteria via stochastic process. Particularly, bacterial community composition and plastic film-sourced pollutants metabolism were evidently affected by soil pH, carbon and nitrogen sources that were mainly derived from the embedded biomass. To sum up, plant biomass embedding as a nature-based strategy (NbS) can positively mediate the decomposition of plastic-sourced pollutants through plastisphere bacteria island effects.

Impact of persistent rain on microplastics distribution and plastisphere community: A field study in the Pearl River, China

Microplastic contamination is a global problem which has been threatening human health and the environment. There is still a knowledge gap about the effect of persistent rain on microplastics distribution and plastisphere community in fluvial environments. In this study, the abundance and composition of microplastics in the sediment and surface water from the Pearl River was investigated. Thirty polymers (10-500 μm) were identified from thirty-eight samples collected at ten sites using the newly developed laser direct infrared (LDIR) technique. The average concentrations of microplastics in the sediment and surface water were 1974 particles kg^-1 and 290 particles L^-1, respectively. Abnormally high concentrations of polyurethanes (PU) were possibly due to particulate pollution from ship antifouling. The persistent rain increased the abundance and diversity of microplastics in the surface water, whereas an opposite trend was observed in the sediment. Sediments could temporarily switch from microplastics sinks to potential sources under the effect of violent hydrodynamic disturbances. Additionally, plastisphere communities and predicted functional profiles indicated significant differences before and after the rain. Our study highlights the important impact of persistent rain on microplastic contamination in the environment.

Unveiling the residual plastics and produced toxicity during biodegradation of polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC) microplastics by mealworms (Larvae of Tenebrio molitor)

Evidence for plastic degradation by mealworms has been reported. However, little is known about the residual plastics derived from incomplete digestion during mealworm-mediated plastic biodegradation. We herein reveal the residual plastic particles and toxicity produced during mealworm-mediated biodegradation of the three most common microplastics, i.e., polyethylene (PE), polystyrene (PS), and polyvinyl chloride (PVC). All three microplastics are effectively depolymerized and biodegraded. We discover that the PVC-fed mealworms exhibit the lowest survival rate (81.3 ± 1.5%) and the highest body weight reduction (15.1 ± 1.1%) among the experimental groups by the end of the 24-day experiment. We also demonstrate that the residual PVC microplastic particles are more difficult to depurate and excrete for the mealworms compared to the residual PE and PS particles by using laser direct infrared spectrometry. The levels of oxidative stress responses, including reactive oxygen species, antioxidant enzyme activities, and lipid peroxidation, are also highest in the PVC-fed mealworms. Sub-micron microplastics and small microplastics are found in the frass of mealworms fed with PE, PS, and PVC, with the smallest particles detected at diameters of 5.0, 4.0, and 5.9 µm, respectively. Our findings provide insights into the residual microplastics and microplastic-induced stress responses in macroinvertebrates under micro(nano)plastics exposure.

New insight into the effect of microplastics on antibiotic resistance and bacterial community of biofilm

Microplastics (MPs) could serve as substrates for microbial colonization and biofilm formation. However, research on the effects of different types of microplastics and natural substrates on biofilm formation and community structure in the presence of antibiotic-resistant bacteria (ARB) is limited. In this study, we employed by means of microcosm experiments to analyze the situation of biofilms conditions, bacterial resistance patterns, antibiotic resistance genes (ARGs) distribution, and bacterial community on different substrates using microbial cultivation, high throughtput sequencing and PCR. The result showed that biofilms on different substrates markedly increased with time, with MPs surfaces formed more biofilm than stone. Analyses of antibiotic resistant showed negligible differences in the resistance rate to the same antibiotic at 30 d, but tetB would be selectively enriched on PP and PET. The microbial communities associated with biofilms on MPs and stones exhibited variations during different stages of formation. Notably, phylum WPS-2 and Epsilonbacteraeota were identified as the dominant microbiomes of biofilms on MPs and stones at 30 d, respectively. Correlation analysis suggested that WPS-2 could potentially be a tetracycline-resistant bacterium, while Epsilonbacteraeota did not correlate with any detected ARB. Our results emphasized the potential threat posed by MPs as attachment carriers for bacteria, particularly ARB, in aquatic environments.

Plastisphere microbiome: Methodology, diversity, and functionality

Broad topics of the plastisphere in various environments are reviewed, including its methodologies, diversity, functionality, and outlook.

Characteristics, sources and influencing factors of atmospheric deposition of microplastics in three different ecosystems of Beijing, China

As the research on microplastics (MPs) has intensified, more attention has been paid to MPs deposition in the atmosphere. This study further explores and compares the characteristics, the possible sources and influencing factors of deposition of MPs in three different ecosystems: forest, agricultural and residential area in Beijing. It was found that the deposited plastics were mostly white or black fibres, with PET and RY as the main MPs types. The range of deposition fluxes was 67.06-461.02 item·m^-2·d^-1, with highest deposition in residential area and lowest in forest, significant differences in MPs characteristics between environments. Based on MPs composition and shape, combined with backward trajectory analysis, the main sources of MPs were found to be textiles. Deposition of MPs was found to be influenced by environmental and meteorological factors. Factors such as gross domestic product and population density had a significant impact on the deposition flux, while wind played a diluting role for atmospheric MPs. The study investigated the characteristics of MPs in different ecosystems which may help to understand the transport patterns of MPs and is of great importance for the management of MPs pollution.

Organismal response to micro(nano)plastics at environmentally relevant concentrations: Toxicity and the underlying mechanisms

The toxic effects of micro(nano)plastics are long-standing, flourishing and fadeless as a research topic because of its' underlying threats to the ecology and human health. Nevertheless, in most of the existing studies, some model organisms are exposed to micro(nano)plastics at a high concentration unlikely to occur in the real environment, and there is limited data available on the impact of micro(nano)plastics at environmentally relevant concentrations (ERC) on environmental organisms. To gain a better insight into micro(nano)plastic toxicity to the environmental organisms, here we integrate the related publications of micro(nano)plastic research at ERC in the past 10 years using a bibliometric analysis, and focus on the analysis of publication trends, research focuses, collaborations, and research status. In addition, we further analyze the 33 final filtered literature, and elucidate the organismal response to micro(nano)plastics at ERC from the perspective of in vivo toxic effects and mechanisms involved. This paper also puts forward some limitations of the current study and some suggestions for future research. Our study may be of great significance in further understanding the ecotoxicity of micro(nano)plastics.

Responses of bacterial communities to microplastics: More sensitive in less fertile soils

Recently, the potential impact of microplastics (MPs) on bacterial communities has risen enormously attention due to the increasing amount of plastic waste generated nowadays. However, there is a lack of clarity due to limited studies on the responses of bacterial communities to MPs exposures in various soil ecosystems. Here, we conducted a soil microcosm experiment to analyze the potential impact of MPs on bacterial communities in farmland soil, forest soil, and sandy soil. The changes in alpha/beta diversity and co-occurrence network of bacterial communities were more significant in farmland soil amended with PS MPs (5 g kg^-1), forest soil amended with PP MPs (5 g kg^-1), and sandy soil amended with PP MPs (1 g kg^-1). Particularly, the bacterial communities in sandy soil with the least soil organic carbon content were disturbed most significantly compared to other treatments. LEfSe analysis revealed that specific bacterial taxa such as phylum Proteobacteria, Actinobacteria, Firmicutes, and genus Sphingomonas, Candidatus Udaeobacter, Gemmatimonas, were sensitive to MPs exposures. Functional annotation showed that perturbation of bacterial communities was related to organic carbon decomposition, nitrogen fixation, nitrate reduction/respiration, etc. In sum, MPs may potentially affect bacterial community structure and functions relevant to carbon/nitrogen cycles at long-term realistic field exposure.

The plastisphere of biodegradable and conventional microplastics from residues exhibit distinct microbial structure, network and function in plastic-mulching farmland

The inhomogeneity of plastisphere and soil may result in different microbial communities, thus potentially affecting soil functions. Biodegradable plastics offer an alternative to conventional plastics, nevertheless, the inadequate end-of-life treatment of biodegradable plastics may release more microplastics. Herein, we collected PE and PBAT/PLA microplastics in plastic-mulching farmland in Hebei, China. The bacterial communities of soil, PE and PBAT/PLA plastisphere were investigated using 16 S high-throughput sequencing. We found that the structure of bacterial communities in PBAT/PLA plastisphere were significantly distinct from PE plastisphere and soil. The alpha diversities in PBAT/PLA plastisphere were significantly lower than PE plastisphere and soil. Statistical analysis of differentially ASVs suggested that PBAT/PLA microplastics act as a filter, enriching taxa with the capability to degrade plastic polymers such as Proteobacteria and Actinobacteria. Compared to PE plastisphere, PBAT/PLA plastisphere has networks of less complexity, lower modularity, and more competitive interactions. Predicted metabolic pathways involved in human diseases, carbohydrate metabolism, amino acid metabolism, and xenobiotic biodegradation and metabolism were promoted in PBAT/PLA plastisphere, along with the facilitation in abundance of genes associated with carbon and nitrogen cycling. Our results highlighted the uniqueness of plastisphere of biodegradable microplastics from conventional microplastics and their potential impact on soil functions.

Microfiber-loaded bacterial community in indoor fallout and air-conditioner filter dust

Microfibers (MFs) are widely existed in indoor air; however, characteristic of microbiota on MFs is largely unknown. In this study, air-borne MFs were collected from fallout or air-conditioner (AC) filter dust in three types of indoor space including living room, dormitory and office. Both plastic and natural MFs were identified by Fourier transform infrared spectroscopy. Ultramicroscopic observation showed dense biofilms adhering on surfaces of MFs. Fallout MFs contained more bacteria but fewer fungi than MFs from AC filter dust. MFs-loaded bacteria were of highest abundance in living rooms, following dormitories and offices. Bacterial community and its diversity were further analyzed by 16S rRNA High-throughput sequencing. Up to 4540 of bacterium OTUs were shared in these MFs samples, unique OTUs in fallout and AC filter samples accounting for 26.3 % and 25.7 % of the total. Compared to MFs fallout, AC filter MFs contained more species of pathogenic bacteria, such as Betaproteobacteriales and Ralstonia, with obviously different β-diversity between two groups. Phenotypic analysis showed that fallout and AC filter MFs bacteria presented high index values of film formation, oxidative stress tolerance and potential pathogenicity. Overall, these results suggest that abundant bacteria including pathogen can be loaded on MFs, and would pose health risks through delivery of indoor MFs.

Indoor microplastics and bacteria in the atmospheric fallout in urban homes

Humans may be exposed to microplastics (MPs) through food, drink, and air. Although several studies have examined indoor environmental MPs, none have yet compared atmospheric MP and bacterial deposition characteristics among rooms in homes. We investigated indoor airborne MPs and bacteria in five room types (bedroom, dining room, living room, bathroom, and study) based on the duration of usage of each room. We identified synthetic polymers (23,889 MP particles of 21 types) and bacterial communities (383 genera belong to 24 phyla) collected through atmospheric deposition in various rooms of 20 homes. The abundance and composition of MPs are related to the duration of usage, human activities, goods, cleanliness, and the composition of occupants (family members) in households. In addition, the homes of elderly families (age 68-81 years) showed higher bacterial concentrations than those of young families (age 28-35 years), indicating that age markedly affects the structure of household microbiota. Furthermore, a significant correlation between MP concentration and bacterial community structure was observed. The abundances of polyamide (PA), polyurethane (PU), and polyethylene (PE) showed positive correlations with the relative abundances of major bacterial phyla. Taken together, our results suggest that various rooms in the home exhibit distinct MP abundances and bacterial structures that may be affected by age, cleanliness, and human activities.

Natural detoxification of antibiotics in the environment: A one health perspective

The extended concept of one health integrates biological, geological, and chemical (bio-geo-chemical) components. Anthropogenic antibiotics are constantly and increasingly released into the soil and water environments. The fate of these drugs in the thin Earth space ("critical zone") where the biosphere is placed determines the effect of antimicrobial agents on the microbiosphere, which can potentially alter the composition of the ecosystem and lead to the selection of antibiotic-resistant microorganisms including animal and human pathogens. However, soil and water environments are highly heterogeneous in their local composition; thus the permanence and activity of antibiotics. This is a case of "molecular ecology": antibiotic molecules are adsorbed and eventually inactivated by interacting with biotic and abiotic molecules that are present at different concentrations in different places. There are poorly explored aspects of the pharmacodynamics (PD, biological action) and pharmacokinetics (PK, rates of decay) of antibiotics in water and soil environments. In this review, we explore the various biotic and abiotic factors contributing to antibiotic detoxification in the environment. These factors range from spontaneous degradation to the detoxifying effects produced by clay minerals (forming geochemical platforms with degradative reactions influenced by light, metals, or pH), charcoal, natural organic matter (including cellulose and chitin), biodegradation by bacterial populations and complex bacterial consortia (including "bacterial subsistence"; in other words, microbes taking antibiotics as nutrients), by planktonic microalgae, fungi, plant removal and degradation, or sequestration by living and dead cells (necrobiome detoxification). Many of these processes occur in particulated material where bacteria from various origins (microbiota coalescence) might also attach (microbiotic particles), thereby determining the antibiotic environmental PK/PD and influencing the local selection of antibiotic resistant bacteria. The exploration of this complex field requires a multidisciplinary effort in developing the molecular ecology of antibiotics, but could result in a much more precise determination of the one health hazards of antibiotic production and release.

An In Situ Depolymerization and Liquid Chromatography-Tandem Mass Spectrometry Method for Quantifying Polylactic Acid Microplastics in Environmental Samples

Polylactic acid (PLA) is the most commonly used biodegradable plastic with rapid growth in recent years. This leads to predictable increased pollution of PLA microplastics (MPs) in the environment. However, quantification methods for the PLA MPs are still lacking. In this study, a method based on alkali-assisted thermal depolymerization and liquid chromatography-tandem mass spectrometry (LC-MS/MS) analysis was developed to quantify PLA MPs. After the background monomer compound was removed, PLA MPs were efficiently depolymerized to lactic acid and detected by LC-MS/MS with a limit of quantification of 18.7 ng/g. The ideal recovery of spiked PLA MPs of 93% was obtained, and the PLA MPs did not need to be separated or extracted in advance from the environmental samples. Using this method, PLA MPs were detected in all the sediment samples of a reservoir at a range of 53.5-491 ng/g dw, and the concentrations decreased with the sediment depth. In addition, after soaking in water at 95 °C for 30 min, approximately 12 μg of PLA MPs was released from a single teabag.

Slower antibiotics degradation and higher resistance genes enrichment in plastisphere

Microplastics (MPs) are increasingly entering the urban aquatic ecosystems, and the environmental significance and health risks of plastisphere, a special biofilm on MPs, have received widespread attention. In this study, MPs of polylactic acid (PLA) and polyvinyl chloride (PVC) and quartzite were incubated in an urban water environment, and the tetracycline (TC) degradation ability was compared. Approximatedly 24% of TC biodegraded in 28 d in the water-quartzite system, which is significantly higher than that in the water-PLA (17.3%) and water-PVC systems (16.7%). Re-incubation of microorganisms in biofilms affirmed that quartzite biofilm has a higher TC degradation capacity than the plastisphere. According to high-throughput sequencing of 16S rRNA and metagenomic analysis, quartzite biofilm contained more abundant potential TC degrading bacteria, genes related to TC degradation (eutG, aceE, and DLAT), and metabolic pathways related to TC degradation. An oligotrophic environment on the quartzite surface might lead to the higher metabolic capacity of quartzite biofilm for unconventional carbons, e.g., TC. It is also found that, compared with quartzite biofilm, the distinct microbes in the plastisphere carried more antibiotic resistance genes (ARGs). Higher affinity of MPs surface to antibiotics may lead to higher antibiotics stress on the plastisphere, which further amplify the carrying capacity for ARGs of microorganisms in the plastisphere. Compared to the nondegradable PVC MPs, surface of the biodegradable PLA plastics harbored significantly higher amounts of biomass and ARGs. Compared to the mineral particles, the capability of plastisphere has lower ability to degrade unconventional carbon sources such as the refractory organic pollutants, due to the abundance of carbon sources (adsorbed organic carbon and endogenous organic carbon) on the MPs surface. Meanwhile, the stronger adsorption capacity for pollutants also leads to higher pollutant stress (such as antibiotic stress) in plastisphere, which in turn affects the microbiological characteristics of the plastisphere itself, such as carrying more ARGs.

The effects of biochar on antibiotic resistance genes (ARGs) removal during different environmental governance processes: A review

Antibiotic resistance genes (ARGs) pollution has been considered as one of the most significant emerging environmental and health challenges in the 21st century, many efforts have been paid to control the proliferation and dissemination of ARGs in the environment. Among them, the biochar performs a positive effect in reducing the abundance of ARGs during different environmental governance processes and has shown great application prospects in controlling the ARGs. Although there are increasing studies on employing biochar to control ARGs, there is still a lack of review paper on this hotspot. In this review, firstly, the applications of biochar to control ARGs in different environmental governance processes were summarized. Secondly, the processes and mechanisms of ARGs removal promoted by biochar were proposed and discussed. Then, the effects of biochar properties on ARGs removal were highlighted. Finally, the future prospects and challenges of using biochar to control ARGs were proposed. It is hoped that this review could provide some new guidance for the further research of this field.

Differences in the Plastispheres of Biodegradable and Non-biodegradable Plastics: A Mini Review

There has been a steady rise in the production and disposal of biodegradable plastics. Unlike the microorganisms present in the biofilms on non-biodegradable plastic surfaces (the “plastisphere”), the plastisphere of biodegradable plastic has not been well-characterized. As the polymer structure of biodegradable plastic has a higher microbial affinity than that of non-biodegradable plastic, their plastispheres are assumed to be different. This review summarizes the reported differences in microbial communities on the surface of biodegradable and non-biodegradable plastics, discusses the driving forces behind these differences, and discusses the potential environmental risks. Overall, the plastisphere biomass on the surface of non-biodegradable plastic was observed to be lower than that of biodegradable plastic. The community structure of microbes in both plastispheres was diverse, mainly due to the properties of the plastic surface, such as surface charge, hydrophilicity/hydrophobicity, roughness, and bioavailability of polymer components for microbes. Further research should focus on developing biodegradable plastic that degrade faster in the environment, revealing the mechanism of enrichment of ARGs and potential pathogens on plastics, and understanding the potential influence of plastispheres on the evolution and selection of plastic-degrading microbial potential.

An Overview of Antibiotic Resistance and Abiotic Stresses Affecting Antimicrobial Resistance in Agricultural Soils

Excessive use of antibiotics in the healthcare sector and livestock farming has amplified antimicrobial resistance (AMR) as a major environmental threat in recent years. Abiotic stresses, including soil salinity and water pollutants, can affect AMR in soils, which in turn reduces the yield and quality of agricultural products. The objective of this study was to investigate the effects of antibiotic resistance and abiotic stresses on antimicrobial resistance in agricultural soils. A systematic review of the peer-reviewed published literature showed that soil contaminants derived from organic and chemical fertilizers, heavy metals, hydrocarbons, and untreated sewage sludge can significantly develop AMR through increasing the abundance of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARBs) in agricultural soils. Among effective technologies developed to minimize AMR’s negative effects, salinity and heat were found to be more influential in lowering ARGs and subsequently AMR. Several strategies to mitigate AMR in agricultural soils and future directions for research on AMR have been discussed, including integrated control of antibiotic usage and primary sources of ARGs. Knowledge of the factors affecting AMR has the potential to develop effective policies and technologies to minimize its adverse impacts.

Key knowledge gaps for One Health approach to mitigate nanoplastic risks

There are increasing concerns over the threat of nanoplastics to environmental and human health. However, multidisciplinary barriers persist between the communities assessing the risks to environmental and human health. As a result, the hazards and risks of nanoplastics remain uncertain. Here, we identify key knowledge gaps by evaluating the exposure of nanoplastics in the environment, assessing their bio-nano interactions, and examining their potential risks to humans and the environment. We suggest considering nanoplastics a complex and dynamic mixture of polymers, additives, and contaminants, with interconnected risks to environmental and human health. We call for comprehensive integration of One Health approach to produce robust multidisciplinary evidence to nanoplastics threats at the planetary level. Although there are many challenges, this holistic approach incorporates the relevance of environmental exposure and multi-sectoral responses, which provide the opportunity to identify the risk mitigation strategies of nanoplastics to build resilient health systems.