Potential risks of microplastics combined with superbugs: Enrichment of antibiotic resistant bacteria on the surface of microplastics in mariculture system

Bacterial pathogen assemblages on microplastic biofilms in coastal waters

Microplastic pollution in coastal ecosystems poses significant environmental risks. Microplastic biofilms were investigated through field incubation in coastal waters over a 21-day period to identify harmful microorganisms. Screening results indicated generally low abundance but highly diverse and variable nature of harmful pathogens on microplastics, largely governed by polymer type in conjunction with water usage. Typhoon shelter exhibited the highest pathogen abundance in both seawater and microplastic biofilms, with the most dominant pathogen species on microplastic biofilms being the atypical Corynebacterium variabile primarily enriched on polystyrene biofilms. Other harmful species, such as Vibrio, Acinetobacter, and Pseudomonas, were found sporadically recruited. Functional annotation and network analysis indicated a co-occurrence of pathogen taxa with keystone taxa like Aeromonas, yet no significant correlation with ARGs. This study showed that the assemblage of pathogens in the plastisphere could be influenced by multiple factors, providing a valuable reference for assessing microplastic-related pathogen risks in coastal waters.

Unraveling the role of microplastics in antibiotic resistance: Insights from long-read metagenomics on ARG mobility and host dynamics

As two emerging pollutants, microplastics (MPs) potentially serve as vectors for antibiotic resistance genes (ARGs) in aquatic environments, but the mechanisms driving ARG enrichment remain unclear. This study used long-read metagenomics to investigate ARG mobility and hosts dynamics within the biofilms of MPs and rocks in different water environments. We identified distinct enrichment patterns for microbial communities and ARGs, highlighting the significant role of horizontal gene transfer in ARG enrichment. Specifically, plasmid-encoded ARGs varied significantly among MP biofilms, rock biofilms, and water samples, while chromosome-encoded ARGs remained consistent across these environments, emphasizing the impact of plasmids on ARG enrichment. Despite this, 55.1 % of ARGs were on chromosomes, indicating that host organisms also play a crucial role. The related mechanisms driving ARG enrichment included enhanced cell adhesion, increased transmembrane transporter activity, and responses to environmental stressors, which led to an increased presence of plasmid-encoded ARGs on MP biofilms, facilitating more frequent horizontal gene transfer. Additionally, the diversity of hosts on MPs was notably lower compared to the water column, with specific bacteria, including Herbaspirillu, Limnohabitans, Polaromonas, Variovorax, Rubrivivax, and Thauera significantly driving ARG enrichment. This study highlights key mechanisms and bacterial taxa involved in ARG dynamics on MPs.

Impact of microplastics exposure on the reconfiguration of viral community structure and disruption of ecological functions in the digestive gland of Mytilus coruscus

Microplastics (MPs) pose ecological risks by serving as viral vectors and disrupting host microbiomes. This study investigated the impact of MPs on the digestive gland virome of Mytilus coruscus through an in situ exposure experiment on Xixuan Island, Zhoushan, China, using polyethylene MPs and metagenomic sequencing. MPs biofilms were dominated by lytic viruses (> 99 %) with low diversity (Shannon index = 4.10 ± 0.39), whereas digestive glands harbored a more diverse virome (Shannon index = 7.26 ± 1.26). MPs ingestion significantly reduced virome diversity and altered viral community composition. Functional analysis showed that MPs biofilms were enriched in genes related to genetic processing, carbohydrate metabolism and membrane biogenesis, while transcription- and replication-related genes declined (P < 0.05) in digestive glands post-ingestion. MPs biofilms carried abundant antibiotic resistance genes (ARGs) and virulence factors, selectively enriching multidrug resistance genes (efrA, patB) while reducing functional viral gene abundance. Metal (Zn, Hg, As) and biocide resistance genes were prevalent in MPs biofilms but declined post-ingestion. Additionally, MPs ingestion weakened microbial network stability, potentially impairing immune regulation and metabolic homeostasis. These findings underscore MPs' role in shaping viral communities and spreading resistance genes, heightening ecological risks in marine environments.

Microplastics: Hidden drivers of antimicrobial resistance in aquatic systems

Microplastics (MPs) in aquatic ecosystems readily promote biofilm formation, creating the plastisphere, a dynamic interface that interacts with environmental pollutants and acts as a reservoir for microorganisms. Recent studies emphasize the plastisphere's contribution to the spread of pathogens, antibiotic-resistant genes (ARGs), and antimicrobial resistance (AMR) within aquatic organisms and across diverse environments, a phenomenon collectively called the 'Plastiome'. Although the prevalence and effects of the plastisphere have been studied extensively, a systematic synthesis of updated insights into the behavior of the plastiome is urgently needed. This review explores the development and behavior of plastics, focusing on its interactions with ARGs and pathogens within aquatic ecosystems. Microplastics selectively enrich ARGs and pathogenic microorganisms, fostering unique microbial communities distinct from those in surrounding waters. The plastiome facilitates horizontal ARG propagation, increasing the quantity of antibiotic-resistant pathogens and presenting substantial risks to the hydrosphere and public health. Additionally, key research opportunities are identified and strategies are recommended to advance our understanding of plastiome-driven antibiotic resistance in aquatic environments.

Plastic-mediated transformation: A new route to navigate plasmid-borne antibiotic resistance genes

Among the anthropogenic sources of pollution, accumulation of plastic polymers in aquatic ecosystems is scaling at unprecedented rates and emerging as a new niche for bacterial colonization and horizontal gene transfer (HGT). The current study focuses on determining the ability of bacteria to acquire plasmid DNA from the extracellular environment under exposure to different treatments (soil, CaCl2 salt solution, soil plus CaCl2, Escherichia coli cell-free extract, and plastic debris) that simulate possible conditions experienced by microorganisms in natural environments. The transformation frequency of two plasmids (pACYC:Hyg and pBAV-1k) was tested following two experimental approaches: single species microcosm of E. coli cells (SSM) and bacterial consortium microcosm (BCM) of strains isolated from freshwater ecosystems. Plastic fragments (with consistent results obtained using polypropylene) proved to be remarkably efficient in increasing the bacterial competence towards plasmid DNA uptake as compared to the other conditions. Moreover, the effects of different plastic polymers and four incubation conditions on bacterial DNA transformation were analyzed to gain deeper insight into the exchange of genetic material. Our findings from both experimental approaches demonstrate that simultaneous incubation of microorganisms, plasmids, and plastic fragments enhances the bacterial ability to uptake plasmids and to express genes required for survival under stress conditions. The two microcosm models prove to be promising tools to mimic natural transformation events leading to the dissemination of antibiotic-resistant genes via HGT in the environment.

Presence of microplastic particles increased abundance of pathogens and antimicrobial resistance genes in microbial communities from the Oder river water and sediment

High abundance of microplastic particles (MPs) in the water environment could be a factor in spreading of pathogens and antimicrobial resistance genes (AMR), especially antibiotic resistance genes (ARGs). The aim of our study was to assess changes in the microbial community developing on microplastic surfaces incubated in water from the Oder River-one of Central Europe's major rivers, flowing through three countries (Czechia, Germany, and Poland)-whose diverse, 20,000-km2 catchment area (encompassing industrial, agricultural, and urban regions) ensures a relatively high abundance of microbial communities.Samples of water and sediment were taken from river in Wroclaw area. Then the water was poured into disinfected glass liquid containers and pre-drained sediment was added. Control samples of water and sediment were collected on day 0. Then microplastic particles were added (500 mg; ~ 1 mm). Subsequent sampling was performed after incubation on 7th and 14th day. From each group, samples of sediment and water were collected after the incubation period (n = 5/group), for extraction of microbial DNA and library preparation. Sequencing was performed, using MinION sequencer with 10.4.1 Flow cell. Galaxy Europe platform and R program (v 4.3.3), alpha diversity and PERMANOVA with Benjamini-Hochberg p-value correction for multiple comparisons were used. For identification of biomarker taxa being different between groups, ANCOMBC (Analysis of Compositions of Microbiomes with Bias Correction) was performed. Obtained results shown higher abundance of pathogenic bacteria such as Aeromonas salmonicida Vibrio spp., Escherichia coli or Salmonella after 7 days of incubation in water and sediment. Additionally, after 7 days of incubation numbers of ARGs was higher compared to control group.

Simulated Discharge of Ballast Water Reveals Potential Contribution to Spread of Antibiotic Resistance Genes in Geographically Isolated Receiving Waters

Background/Objectives: The propagation of antibiotic resistance genes (ARGs) poses a huge threat to environmental and human health. The ballast water from ships has been recognized as an important vector of ARGs. However, little is known about how ballast water from geographically isolated water affects ARGs in receiving waters. Methods: Herein, we investigated the changes in ARGs in receiving water by microcosm experiments simulating the discharge of ballast water. Results: The simulated discharge of ballast water increased the abundances of target ARGs, which were 1.3-5.6-fold higher in the mixture of ballast water and receiving water (microcosm M) than in receiving water at the end of the experiment. The enrichment of target ARGs was significantly associated with MGEs. Moreover, the discharge of ballast water changed the microbial communities in receiving water. Further network analysis identified potential ARG hosts, such as Pseudohongiellaa and Amphritea, with the abundance in microcosm M (0.23% and 0.036%) being higher than in receiving water (0.09% and 0.006%), the changes of which might be responsible for ARG variations. Conclusions: Overall, our findings suggest the discharge of ballast water might promote the spread of ARGs in different geographical waters and the corresponding ecological risks should not be ignored.

Comprehensive approaches to managing emerging contaminants in wastewater: identification, sources, monitoring and remediation

Wastewater is a major source of contamination and must be treated before it is discharged into rivers and lakes. Water contaminated with emerging pollutants such as micropollutants, pharmaceuticals, endocrine disruptors (EDs), pesticides, synthetic dyes, toxins and hormones is of major concern due to its potential adverse effects. The accumulation of such pollutants can disbalance trophic levels and has negative ecological impacts and possible health risks. Monitoring and detecting these contaminants is essential for effective mitigation. Ongoing research on emerging contaminants drives the development of new analytical techniques and technologies for detection, monitoring and removal of such contaminants. As the demand for sustainable wastewater management increases, both conventional and advanced detection methods can be practised as treatment strategies. This approach enhances our capacity to detect and measure contaminants in environmental samples, leading to the development of more effective treatment methods. This review provides important insights into different classes of emerging contaminants, their sources as well as environmental and health risks associated with these pollutants. It also examines the major conventional and advanced technologies used to manage emerging contaminants.

Potential ecological risk of microplastics contamination to environment in protect area lakes

Microplastics (MPs) in freshwater have been extensively studied on a global scale. However, a deeper understanding is still required regarding the occurrence characteristics and ecological risks of MPs in protected area lakes(PAL). Here, the study investigated MPs pollution in PAL, outside protected areas lakes (OPAL), and ponds (OPAP) in the eastern Qinghai-Tibetan Plateau, and a comprehensive analysis was conducted comparing lakes or ponds from different income regions. The results showed that PAL has a single source of contamination, while OPAL and OPAP exhibited more diverse MP sources. The surface of all samples showed significant physicochemical changes like oxygen-containing functional groups and potential signs of biodegradation. Microbiome analysis identified potential plastic-degrading bacteria on MPs, which varied by polymer type. Ecological risk assessment revealed that OPAL and OPAP face higher ecological risks, particularly from polymers like PVC and PC, while PAL has low risk. However, we should also consider the environmental changes over the past 100 years of history in this region and emphasize the environmental health of PAL. Notably, MPs pollution is more severe in lower-middle-income regions, highlighting the urgent need for stricter controls.

Microplastic interactions with co-existing pollutants in water environments: Synergistic or antagonistic roles on their removal through current remediation technologies

Composite water pollution, caused by microplastics (MPs) and co-occurring pollutants, is an emerging issue that induces synergistic toxicity. Multidimensional interactions occur between MPs and co-existing pollutants in a composite system, which alter the behavior of each component, resulting in unpredictable effects on the treatment processes. However, significant gaps exist in current review papers regarding MP‒pollutant interaction mechanisms and the corresponding synergistic or antagonistic effects on their removal processes. This review comprehensively describes the latest research in composite water pollution caused by MPs and various other pollutants with different compositions and states, systematically discusses their interaction mechanisms, and critically evaluates the impact of co-existing contaminants on the treatment performance of current remediation technologies. Based on current research progress and gaps, opportunities, challenges, and perspectives for future research directions are proposed. This review highlights state-of-the-art research related to composite water pollution caused by MPs and various pollutants, which is expected to inspire new strategies for the effective removal of multiple contaminants from the aquatic environment.

Antibiotic resistance in plastisphere

Microbial life on plastic debris, called plastisphere, has invoked special attention on aquatic ecosystems as emerging habitats for antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB). There is scarce information concerning how properties of plastics influence ARGs and ARB, the effect of biofilms on enrichment of ARGs and ARB, and, especially, the influence of plastic transformation on ARGs and ARB. Limited research has shown that microplastic (MP) surfaces influence proliferation of antibiotic resistance (AR), aged MPs exhibit increased toxicity due to more adsorption-desorption of AR, and MP transformation is correlated with disseminating AR. Prevention measures of AR include minimizing MP releasing into aquatic environments and sewage treatment plants. The future research should aim to identify the interface mechanisms of transformed MNPs and antibiotics alone, or mixed with other contaminants, property changes of MNPs, and associated toxicity evaluation.

The nexus of microplastics, food and antimicrobial resistance in the context of aquatic environment: Interdisciplinary linkages of pathways

The exponential rise in plastic production since the mid-20th century has led to the widespread existence of microplastics in various ecosystems, posing significant environmental and health concerns. Microplastics, defined as plastic particles smaller than 5 mm, have infiltrated diverse environments, including oceans, freshwater bodies, and even remote Arctic ice. Their ability to absorb toxic chemicals and serve as vectors for microbial colonization raises concerns about their impacts on aquatic organisms and human health. This review examines the pathways by which microplastics infiltrate the food chain, highlighting their presence in various food items consumed by humans. Furthermore, it explores the nexus between microplastics and antimicrobial resistance (AMR), elucidating how microorganisms inhabiting plastic surfaces facilitate the transmission of antibiotic resistance genes (ARGs). The review underscores the urgent need for interdisciplinary research integrating environmental science, microbiology, public health, and policy to address the multifaceted challenges posed by microplastics. Standardized protocols for sampling and analysis are essential to enable meaningful comparisons across research and regions. By collectively addressing these challenges, we can strive towards a more sustainable and resilient future for ecosystems and human societies.

Microplastics Exacerbated Conjugative Transfer of Antibiotic Resistance Genes during Ultraviolet Disinfection: Highlighting Difference between Conventional and Biodegradable Ones

Microplastics (MPs) have been confirmed as a hotspot for antibiotic resistance genes (ARGs) in wastewater. However, the impact of MPs on the transfer of ARGs in wastewater treatment remains unclear. This study investigated the roles and mechanisms of conventional (polystyrene, PS) and biodegradable (polylactic acid, PLA) MPs in the conjugative transfer of ARGs during ultraviolet disinfection. The results showed that MPs significantly facilitated the conjugative transfer of ARGs compared with individual ultraviolet disinfection, and PSMPs exhibited higher facilitation than PLAMPs. The facilitation effects were attributed to light shielding and the production of reactive oxygen species (ROS) and nanoplastics from ultraviolet irradiation of MPs. The light shielding of MPs protected the bacteria and ARGs from ultraviolet inactivation. More importantly, ROS and nanoplastics generated from irradiated MPs induced intracellular oxidative stress on bacteria and further increased the cell membrane permeability and intercellular contact, ultimately enhancing the ARG exchange. The greater fragmentation of PSMPs than PLAMPs resulted in a higher intracellular oxidative stress and a stronger enhancement. This study highlights the concerns of conventional and biodegradable MPs associated with the transfer of ARGs during wastewater treatment, which provides new insights into the combined risks of MPs and ARGs in the environment.

Effects of aging of polyethylene microplastics and polystyrene nanoplastics on antibiotic resistance gene transfer during primary sludge fermentation

The increasing presence of nano and microplastics (NPs/MPs) in wastewater treatment plants and their inevitable accumulation in the sludge has raised serious concerns in recent years. This study investigated the effects of pristine and aged polyethylene microplastics (PEMPs), polystyrene nanoplastics (PsNPs), and their mixtures on the primary sludge fermentation process. Pristine MPs/NPs (150 μg/L and 2 g/L for PsNPs and PEMPs, respectively) underwent two weeks of weathering in the presence of humic and alginic acids. The results from a batch fermentation experiment (15 days, pH 10) revealed that the exposure to aged PEMPs/PsNPs experienced greater VFA production than pristine samples. Notably, the aged PEMPs/PsNPs mixture showed a 23.12% increase in VFA production over the pristine mixture. The relative abundance and total concentration of antibiotic resistance genes (ARGs) increased in all PEMPs/PsNPs batches compared to the control, with the most significant rise in total ARGs observed in the aged PEMPs sample. Aged PEMPs exhibited a 26.22-fold increase in tetA genes, while aged mix samples showed a 19.68-fold increase in tetM genes compared to their pristine counterparts. Both pristine and aged PEMPs/PsNPs, particularly the aged PEMPs adversely affected the microbial communities at the genus level and altered the microbial structure. Microbial richness and diversity were enhanced in samples exposed to pristine PEMPs/PsNPs and aged PsNPs but decreased in aged PEMPs and in the aged mixture group, suggesting a negative impact of aged polyethylene microplastics on microbial communities. Correlation analysis suggested that phyla Planctomycetes, Proteobacteria, and TM7 are potential hosts of ARGs. These findings manifest the substantial effects of aged nano/microplastics compared to their pristine forms, emphasizing the complex interplay between various forms of PEMPs/PsNPs and microbial dynamics in sludge fermentation processes.

Combined pollution of tetracyclines and microplastics in the aquatic environment: Insights into the occurrence, interaction mechanisms and effects

Tetracyclines, a widely used class of antibiotics, and synthetic plastic products are both prevalent in the environment. When released into water bodies, these pollutants can pose significant risks due to their daily influx into aquatic ecosystems. Microplastics can adsorb tetracyclines, acting as a transport vector that enhances their impact on aquatic species. Understanding the co-exposure effects of microplastics and tetracyclines is crucial. This review comprehensively examines the occurrence and distribution of microplastics and tetracyclines across various environmental contexts. The interactions between these two contaminants are primarily driven by electrostatic interactions, hydrophobic effects, hydrogen bonding, π-π interactions, and others. Factors such as the presence of heavy metals, ions, and dissolved organic matter can influence the adsorption and desorption of tetracyclines onto microplastics. The stability of microplastic-tetracycline complexes is highly dependent on pH conditions. The combined pollution tetracyclines and microplastics leads to negative impacts on marine species. Future research should focus on understanding the adsorption behavior of tetracyclines on microplastics and developing effective treatment techniques for these contaminants in aquatic environments.

Tire wear particles enhance horizontal gene transfer of antibiotic resistance genes in aquatic ecosystems

Microplastics (MPs) have introduced new surfaces for biofilm development and gene exchange among bacteria. We investigated Tire Wear Particles (TWPs) for their involvement in horizontal gene transfer (HGT), particularly in relation to associated metals in the matrices of TWPs. We employed red-fluorescently tagged E. coli strain as a donor with green-fluorescently tagged, broad-host-range plasmid pKJK5, resistant to trimethoprim. As a recipient, we utilized Pseudomonas sp. and a natural lake microbial community. HGT activity on TWPs was determined and compared with that on polystyrene (PS) (with and without metals), and chitosan, which was used as a natural surface. Exposure to TWPs significantly enhanced HGT frequency of antibiotic resistance gene (ARG) from donor to recipient compared to PS and chitosan, and metals of TWPs further promoted HGT. HGT frequency on TWPs with Pseudomonas sp. was found to be 10-3 at 30 °C. in the lake community, it was similarly high already at 25 °C suggesting a higher permissiveness of the natural microbial community towards ARG at lower temperatures. This study sheds light on the potential impact of TWPs in promoting HGT, forming the basis for health risk assessments of TWPs and more generally of MP pollution in various aquatic ecosystems.

Biofilm formation on microplastics and interactions with antibiotics, antibiotic resistance genes and pathogens in aquatic environment

Microplastics (MPs) in aquatic environments easily support biofilm development, which can interact with other environmental pollutants and act as harbors for microorganisms. Recently, numerous studies have investigated the fate and behavior of MP biofilms in aquatic environments, highlighting their roles in the spread of pathogens and antibiotic resistance genes (ARGs) to aquatic organisms and new habitats. The prevalence and effects of MP biofilms in aquatic environments have been extensively investigated in recent decades, and their behaviors in aquatic environments need to be synthesized systematically with updated information. This review aims to reveal the development of MP biofilm and its interactions with antibiotics, ARGs, and pathogens in aquatic environments. Recent research has shown that the adsorption capabilities of MPs to antibiotics are enhanced after the biofilm formation, and the adsorption of biofilms to antibiotics is biased towards chemisorption. ARGs and microorganisms, especially pathogens, are selectively enriched in biofilms and significantly different from those in surrounding waters. MP biofilm promotes the propagation of ARGs through horizontal gene transfer (HGT) and vertical gene transfer (VGT) and induces the emergence of antibiotic-resistant pathogens, resulting in increased threats to aquatic ecosystems and human health. Some future research needs and strategies in this review are also proposed to better understand the antibiotic resistance induced by MP biofilms in aquatic environments.

The role of marine bacteria in modulating the environmental impact of heavy metals, microplastics, and pesticides: a comprehensive review

Bacteria assume a pivotal role in mitigating environmental issues associated with heavy metals, microplastics, and pesticides. Within the domain of heavy metals, bacteria exhibit a wide range of processes for bioremediation, encompassing biosorption, bioaccumulation, and biotransformation. Toxigenic metal ions can be effectively sequestered, transformed, and immobilized, hence reducing their adverse environmental effects. Furthermore, bacteria are increasingly recognized as significant contributors to the process of biodegradation of microplastics, which are becoming increasingly prevalent as contaminants in marine environments. These microbial communities play a crucial role in the colonization, depolymerization, and assimilation processes of microplastic polymers, hence contributing to their eventual mineralization. In the realm of pesticides, bacteria play a significant role in the advancement of environmentally sustainable biopesticides and the biodegradation of synthetic pesticides, thereby mitigating their environmentally persistent nature and associated detrimental effects. Gaining a comprehensive understanding of the intricate dynamics between bacteria and anthropogenic contaminants is of paramount importance in the pursuit of technologically advanced and environmentally sustainable management approaches.

A comprehensive review of antibiotic resistance gene contamination in agriculture: Challenges and AI-driven solutions

Since their discovery, the prolonged and widespread use of antibiotics in veterinary and agricultural production has led to numerous problems, particularly the emergence and spread of antibiotic-resistant bacteria (ARB). In addition, other anthropogenic factors accelerate the horizontal transfer of antibiotic resistance genes (ARGs) and amplify their impact. In agricultural environments, animals, manure, and wastewater are the vectors of ARGs that facilitate their spread to the environment and humans via animal products, water, and other environmental pathways. Therefore, this review comprehensively analyzed the current status, removal methods, and future directions of ARGs on farms. This article 1) investigates the origins of ARGs on farms, the pathways and mechanisms of their spread to surrounding environments, and various strategies to mitigate their spread; 2) determines the multiple factors influencing the abundance of ARGs on farms, the pathways through which ARGs spread from farms to the environment, and the effects and mechanisms of non-antibiotic factors on the spread of ARGs; 3) explores methods for controlling ARGs in farm wastes; and 4) provides a comprehensive summary and integration of research across various fields, proposing that in modern smart farms, emerging technologies can be integrated through artificial intelligence to control or even eliminate ARGs. Moreover, challenges and future research directions for controlling ARGs on farms are suggested.

Microplastics exacerbate the ecological risk of antibiotic resistance genes in wetland ecosystem

Wetlands are vital components of the global ecosystem, significantly influencing the retention and dissemination of microplastics (MPs) and antibiotic resistance genes (ARGs). However, the effects of different types of MPs on the environmental dynamics of ARGs within these ecosystems remain poorly understood. This study focused on the distribution and composition of ARGs associated with two primary types of MPs-polyethylene and polypropylene-within the Poyang Lake wetland, the largest freshwater lake in China, utilizing metagenomic analysis. The findings demonstrated that the bacterial communities and ARG profiles in the plastisphere were markedly distinct from those in the surrounding water. Specifically, thirteen opportunistic pathogens and forty subtypes of ARGs, primarily related to multidrug, bacitracin, and β-lactam resistance, were identified in the plastisphere. Notably, polyethylene exhibited four times more specific ARG subtypes than polypropylene. Procrustes analysis combined with network analysis indicated a lack of strong correlation between ARG abundance and bacterial populations, suggesting potential horizontal transfer of ARGs within the microbiota of the plastisphere. Additionally, three novel and functional β-lactamase genes were identified within this environment. This investigation highlights the role of MPs as reservoirs for ARGs, facilitating their exchange and posing risks to both ecological integrity and human health, thereby underscoring the need for increased attention in future research efforts.

Versatile and Portable Cas12a-mediated Detection of Antibiotic Resistance Markers

Antimicrobial resistance (AMR) is a global public health problem particularly accentuated in low- and middle-income countries, largely due to a lack of access to sanitation and hygiene, lack of awareness and knowledge, and the inadequacy of molecular laboratories for timely and accurate surveillance programs. This study introduces a versatile molecular detection toolbox (C12a) for antibiotic resistance gene markers using CRISPR/Cas12a coupled to PCR. Our toolbox can detect less than 3×10-7 ng of DNA (100 attoMolar) or 102 CFU/mL. High concordance was observed when comparing the C12a toolbox with sequenced genomes and antibiotic susceptibility tests for the blaCTX-M-15 and floR antibiotic resistance genes (ARGs), which confer resistance to cefotaxime and other β-lactams, and amphenicols, respectively. C12aINT, designed to detect the Integrase 1 gene, confirmed a high prevalence of the integrase/integron system in E. coli containing multiple ARGs. The C12a toolbox was tested across a wide range of laboratory infrastructure including a portable setup. When combined with lateral flow assays (LFA), C12a exhibited competitive performance, making it a promising solution for on-site ARG detection. Altogether, this work presents a collection of molecular tools (primers, crRNAs, probes) and validated assays for rapid, versatile, and portable detection of antibiotic resistance markers, highlighting the C12a toolbox potential for applications in surveillance and ARG identification in clinical and environmental settings.

Environmental Antimicrobial Resistance: Implications for Food Safety and Public Health

Antimicrobial resistance (AMR) is a serious global health issue, aggravated by antibiotic overuse and misuse in human medicine, animal care, and agriculture. This study looks at the different mechanisms that drive AMR, such as environmental contamination, horizontal gene transfer, and selective pressure, as well as the severe implications of AMR for human and animal health. This study demonstrates the need for concerted efforts across the scientific, healthcare, agricultural, and policy sectors to control the emergence of AMR. Some crucial strategies discussed include developing antimicrobial stewardship (AMS) programs, encouraging targeted narrow-spectrum antibiotic use, and emphasizing the significance of strict regulatory frameworks and surveillance systems, like the Global Antimicrobial Resistance and Use Surveillance System (GLASS) and the Access, Watch, and Reserve (AWaRe) classification. This study also emphasizes the need for national and international action plans in combating AMR and promotes the One Health strategy, which unifies environmental, animal, and human health. This study concludes that preventing the spread of AMR and maintaining the effectiveness of antibiotics for future generations requires a comprehensive, multidisciplinary, and internationally coordinated strategy.

Plastisphere in a low-pollution mountain river: Influence of microplastics on survival of pathogenic bacteria

Microplastics (MPs) are found even in remote and low-pollution freshwater ecosystems. However, the microbial communities associated with MPs in these environments remain poorly understood. We characterized the plastisphere in a low-pollution riverine ecosystem and evaluated the influence of different MPs in the persistence of pathogens in such environments. A mixture of MPs (MPs Mix) composed of polyethylene (PE), polypropylene (PP) and polyethylene terephthalate (PET), was submerged at three locations (L1, L2 and L3) in the river. For comparison purposes, water and sand communities were also analyzed. Our results revealed distinct bacterial communities on MPs compared to those in water or on the natural substrate (sand). However, the resemblance between the plastisphere and communities on natural particles was higher than what has been reported for polluted ecosystems. Although pathogens were predominantly enriched in the water, a few genera (e.g. Acinetobacter, Legionella and Mycobacterium) were enriched in the plastisphere. The abundance of antibiotic resistance genes did not differ significantly between water, sand, and MPs. The influence of different MPs (PE, PP, PET) on the persistence of antibiotic-resistant pathogens (i.e. cefotaxime-resistant Escherichia coli and meropenem-resistant Enterobacter kobei) in unpolluted water was assessed in microcosms. Significant differences were observed between the microcosms with MPs and those with natural particles (sand), after a 36-day exposure. A significantly higher persistence of the pathogens was registered in microcosms with PE and PET. Our results provide new insights into the plastisphere in non-pollution environments and demonstrate that even in these settings, MPs can facilitate the survival and dissemination of pathogens.

Sources, interactions, influencing factors and ecological risks of microplastics and antibiotic resistance genes in soil: A review

Microplastics (MPs) and antibiotic resistance genes (ARGs) are gaining increasing attention as they pose a threat to the ecological environment and human health as emerging contaminants. MPs has been proved to be a hot spot in ARGs, and although it has been extensively studied in water environment, the results of bibliometrics statistical analysis in this paper showed that relevant studies in soil ecological environment are currently in the initial stage. In view of this, the paper provides a systematic review of the sources, interactions, influencing factors, and ecological risks associated with MPs and ARGs in soil environments. Additionally, the mechanism and influencing factors of plastisphere formation and resistance are elaborated in detail. The MPs properties, soil physicochemical properties, soil environmental factors and agricultural activities are the primarily factors affecting the interaction between MPs and ARGs in soil. Challenges and development directions of related research in the future are also prospected. It is hoped that the review could assist in a deeper comprehension and exploration of the interaction mechanism between MPs and ARGs in soil as well as the function of MPs in the transmission process of ARGs among diverse environmental media and organisms, and provide theory basis and reference for the MPs and ARGs pollution control and remediation in soil.

Taxonomic variation, plastic degradation, and antibiotic resistance traits of plastisphere communities in the maturation pond of a wastewater treatment plant

Wastewater treatment facilities can filter out some plastics before they reach the open environment, yet microplastics often persist throughout these systems. As they age, microplastics in wastewater may both leach and sorb pollutants and fragment to provide an increased surface area for bacterial attachment and conjugation, possibly impacting antimicrobial resistance (AMR) traits. Despite this, little is known about the effects of persistent plastic pollution on microbial functioning. To address this knowledge gap, we deployed five different artificially weathered plastic types and a glass control into the final maturation pond of a municipal wastewater treatment plant in Ōtautahi-Christchurch, Aotearoa/New Zealand. We sampled the plastic-associated biofilms (plastisphere) at 2, 6, 26, and 52 weeks, along with the ambient pond water, at three different depths (20, 40, and 60 cm from the pond water surface). We investigated the changes in plastisphere microbial diversity and functional potential through metagenomic sequencing. Bacterial 16S ribosomal RNA genes composition did not vary among plastic types and glass controls (P = 0.997) but varied among sampling times [permutational multivariate analysis of variance (PERMANOVA), P = 0.001] and depths (PERMANOVA, P = 0.011). Overall, there was no polymer-substrate specificity evident in the total composition of genes (PERMANOVA, P = 0.67), but sampling time (PERMANOVA, P = 0.002) and depth were significant factors (PERMANOVA, P = 0.001). The plastisphere housed diverse AMR gene families, potentially influenced by biofilm-meditated conjugation. The plastisphere also harbored an increased abundance of genes associated with the biodegradation of nylon, or nylon-associated substances, including nylon oligomer-degrading enzymes and hydrolases.IMPORTANCEPlastic pollution is pervasive and ubiquitous. Occurrences of plastics causing entanglement or ingestion, the leaching of toxic additives and persistent organic pollutants from environmental plastics, and their consequences for marine macrofauna are widely reported. However, little is known about the effects of persistent plastic pollution on microbial functioning. Shotgun metagenomics sequencing provides us with the necessary tools to examine broad-scale community functioning to further investigate how plastics influence microbial communities. This study provides insight into the functional consequence of continued exposure to waste plastic by comparing the prokaryotic functional potential of biofilms on five types of plastic [linear low-density polyethylene (LLDPE), nylon-6, polyethylene terephthalate, polylactic acid, and oxygen-degradable LLDPE], glass, and ambient pond water over 12 months and at different depths (20, 40, and 60 cm) within a tertiary maturation pond of a municipal wastewater treatment plant.

Aged Microplastics and Antibiotic Resistance Genes: A Review of Aging Effects on Their Interactions

Background: Microplastic aging affects the dynamics of antibiotic resistance genes (ARGs) on microplastics, yet no review presents the effects of microplastic aging on the associated ARGs. Objectives: This review, therefore, aims to discuss the effects of different types of microplastic aging, as well as the other pollutants on or around microplastics and the chemicals leached from microplastics, on the associated ARGs. Results: It highlights that microplastic photoaging generally results in higher sorption of antibiotics and ARGs due to increased microplastic surface area and functional group changes. Photoaging produces reactive oxygen species, facilitating ARG transfer by increasing bacterial cell membrane permeability. Reactive oxygen species can interact with biofilms, suggesting combined effects of microplastic aging on ARGs. The effects of mechanical aging were deduced from studies showing larger microplastics anchoring more ARGs due to rough surfaces. Smaller microplastics from aging penetrate deeper and smaller places and transport ARGs to these places. High temperatures are likely to reduce biofilm mass and ARGs, but the variation of ARGs on microplastics subjected to thermal aging remains unknown due to limited studies. Biotic aging results in biofilm formation on microplastics, and biofilms, often with unique microbial structures, invariably enrich ARGs. Higher oxidative stress promotes ARG transfer in the biofilms due to higher cell membrane permeability. Other environmental pollutants, particularly heavy metals, antibacterial, chlorination by-products, and other functional genes, could increase microplastic-associated ARGs, as do microplastic additives like phthalates and bisphenols. Conclusions: This review provides insights into the environmental fate of co-existing microplastics and ARGs under the influences of aging. Further studies could examine the effects of mechanical and thermal MP aging on their interactions with ARGs.

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

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

Selective Labeling of Small Microplastics with SERS-Tags Based on Gold Nanostars: Method Optimization Using Polystyrene Beads and Application in Environmental Samples

Microplastics pollution is being unanimously recognized as a global concern in all environments. Routine analysis protocols foresee that samples, which are supposed to contain up to hundreds of microplastics, are eventually collected on nanoporous filters and inspected by microspectroscopy techniques like micro-FTIR or micro-Raman. All particles, whether made of plastic or not, must be inspected one by one to detect and count microplastics. This makes it extremely time-consuming, especially when Raman is adopted, and indeed mandatory for the small microplastic fraction. Inspired by the principles of cell labeling, the present study represents the first report in which gold nanostars (AuNS) are functionalized to act as SERS-tags and used to selectively couple to microplastics. The intrinsic bright signals provided by the SERS-tags are used to run a quick scan over a wide filter area with roughly 2 orders of magnitude shorter analysis time in respect of state of the art in micro- and nanoplastics detection by μ-Raman. The applicability of the present protocol has been validated at the proof-of-concept level on both fabricated and real offshore marine samples. It is indeed worth mentioning that a SERS-based approach is herein successfully applied on filters and protocols routinely adopted in environmental microplastics monitoring, paving the way for future implementations and applications.

Horizontal gene transfer plays a crucial role in the development of antibiotic resistance in an antibiotic-free shrimp farming system

Antibiotic selective pressure in aquaculture systems often results in the antibiotic resistance genes (ARGs) proliferation. Nonetheless, a paucity of data exists concerning the mechanisms of ARGs development in aquaculture systems without the influences of antibiotics. This study utilized metagenomic approaches to elucidate the dynamics and transfer mechanisms of ARGs throughout the aquaculture of Pacific white shrimp. A marked change in the resistome was observed throughout the aquaculture without antibiotics. The total ARGs relative abundance increased from 0.05 to 0.33 by day 90 of cultivation, with even higher in mixed wastewater (0.44). Both bacterial communities and mobile genetic elements play pivotal roles in the development of ARGs. Metagenome-assembled genomes showed enrichment of environmentally intrinsic ARGs on chromosomes including macB and mdtK. The plasmid-mediated horizontal transfer was recognized as a principal factor contributing to the rise of ARGs, particularly for tetG and floR, and this led to an escalation of resistance risk, peaking at a risks core of 35.43 on day 90. This study demonstrates that horizontal gene transfer plays a crucial role in ARGs development without antibiotic pressure, which can provide a theoretical foundation for controlling ARGs proliferation in aquaculture systems.

River waters in Greece: A reservoir for clinically relevant extended-spectrum-β-lactamases-producing Escherichia coli

In the current study, the genotypic characteristics such as antimicrobial resistance and virulence genes, and plasmid replicons and phenotypic characteristics such as biofilm formation and antimicrobial resistance of 87 extended-spectrum beta-lactamase (ESBL)-producing E. coli (ESBL-Ec) isolated from 7 water bodies in northern Greece were investigated. Our data show a high prevalence (60.0 %) of ESBL-Ec in surface waters that exhibit high genetic diversity, suggesting multiple sources of their transmission into the aquatic environment. When evaluating the antimicrobial resistance of isolates, wide variation in their resistance profiles has been detected, with all isolates being multi-drug resistant (MDR). Regarding biofilm formation capacity and phylogenetic groups, the majority (54.0 %, 47/87) of ESBL-Ec were classified as no biofilm producers mainly assigned to phylogroup A (35.6 %; 31/87), followed by B2 (26.5 %; 23/87). PCR screening showed that a high proportion of the isolates tested positive for the blaCTX-M-1 group genes (69 %, 60/87), followed by blaTEM (55.2 %, 48/87), blaOXA (25.3 %, 22/87) and blaCTX-M-9 (17.2 %, 15/87). A subset of 28 ESBL-Ec strains was further investigated by applying whole genome sequencing (WGS), and among them, certain clinically significant sequence types were identified, such as ST131 and ST10. The corresponding in silico analysis predicted all these isolates as human pathogens, while a significant proportion of WGS-ESBL-Ec were assigned to extraintestinal pathogenic E. coli (ExPEC; 32.1 %), and urinary pathogenic E. coli (UPEC; 28.6 %) pathotypes. Comparative phylogenetic analysis, showed that the genomes of the ST131-O25:H4-H30 isolates are genetically linked to the human clinical strains. Here, we report for the first time the detection of a plasmid-mediated mobile colistin resistance gene in ESBL-Ec in Greece isolated from an environmental source. Overall, this study underlines the role of surface waters as a reservoir for antibiotic resistance genes and for presumptive pathogenic ESBL-Ec.

Plastic induced urinary tract disease and dysfunction: a scoping review

INTRODUCTION

In 2019 the World Health Organisation published a report which concluded microplastics in drinking water did not present a threat to human health. Since this time a plethora of research has emerged demonstrating the presence of plastic in various organ systems and their deleterious pathophysiological effects.

METHODS

A scoping review was undertaken in line with recommendations from the Johanna Briggs Institute. Five databases (PubMed, SCOPUS, CINAHL, Web of Science and EMBASE) were systematically searched in addition to a further grey literature search.

RESULTS

Eighteen articles were identified, six of which investigated and characterised the presence of microplastics and nanoplastics (MNPs) in the human urinary tract. Microplastics were found to be present in kidney, urine and bladder cancer samples. Twelve articles investigated the effect of MNPs on human cell lines associated with the human urinary tract. These articles suggest MNPs have a cytotoxic effect, increase inflammation, decrease cell viability and alter mitogen-activated protein kinases (MAPK) signalling pathways.

CONCLUSION

Given the reported presence MNPs in human tissues and organs, these plastics may have potential health implications in bladder disease and dysfunction. As a result, institutions such as the World Health Organisation need to urgently re-evaluate their position on the threat of microplastics to public health.

IMPACT STATEMENT

This scoping review highlights the rapidly emerging threat of microplastic contamination within the human urinary tract, challenging the World Health Organisation's assertion that microplastics pose no risk to public health. The documented cytotoxic effects of microplastics, alongside their ability to induce inflammation, reduce cell viability and disrupt signalling pathways, raise significant public health concerns relating to bladder cancer, chronic kidney disease, chronic urinary tract infections and incontinence. As a result, this study emphasises the pressing need for further research and policy development to address the challenges surrounding microplastic contamination.

Vehicle transmission of antibiotic-resistant pathogens mediated by plastic debris in aquatic ecosystems

Plastic materials are emerging environmental pollutants acting as potential vehicles for accumulation and spread of multidrug-resistant bacteria. The current study investigates the role of plastics in favoring the dispersal of specific pathogens and their associated antibiotic resistant genes (ARGs). Artificial plastic substrates (APSs) were submerged in seven sampling points of Lake Bracciano (Italy), and after one-month both APSs and raw water (RW) samples were collected. Through the combination of standard microbiological and biochemical techniques, 272 bacterial strains were identified and characterized for antibiotic resistant profiling. Our results revealed a notable difference in terms of diversity and abundance of pathogenic bacteria recovered from APSs, compared to RW. In addition, higher resistance patterns were detected in APSs isolates, with frequent appearance of relevant ARGs and class 1 integrons. These findings reinforce the idea that plastic materials in aquatic ecosystems serve as a reservoir for superbugs, significantly contributing to the dissemination of ARGs.

Protective effects of antibiotic resistant bacteria on susceptibles in biofilm: Influential factors, mechanism, and modeling

In environmental biofilms, antibiotic-resistant bacteria facilitate the persistence of susceptible counterparts under antibiotic stresses, contributing to increased community-level resistance. However, there is a lack of quantitative understanding of this protective effect and its influential factors, hindering accurate risk assessment of biofilm resistance in diverse environment. This study isolated an opportunistic Escherichia coli pathogen from soil, and engineered it with plasmids conferring antibiotic resistance. Protective effects of the ampicillin resistant strain (AmpR) on their susceptible counterparts (AmpS) were observed in ampicillin-stress colony biofilms. The concentration of ampicillin delineated protective effects into 3 zones: continuous protection (<1 MIC of AmpS), initial AmpS/R dependent (1-8 MIC of AmpS), and ineffective (>8 MIC of AmpS). Intriguingly, Zone 2 exhibited a surprising "less is more" phenomenon tuned by the initial AmpS/R ratio, where biofilm with an initially lower AmpR (1:50 vs 50:1) harbored 30-90 % more AmpR after 24 h growth under antibiotic stress. Compared to AmpS, AmpR displayed superiority in adhesion, antibiotic degradation, motility, and quorum sensing, allowing them to preferentially colonize biofilm edge and areas with higher ampicillin. An agent-based model incorporating protective effects successfully simulated tempo-spatial dynamics of AmpR and AmpS influenced by antibiotic stress and initial AmpS/R. This study provides a holistic view on the pervasive but poorly understood protective effects in biofilm, enabling development of better risk assessment and precisely targeted control strategies of biofilm resistance in diverse environment.

A review focusing on mechanisms and ecological risks of enrichment and propagation of antibiotic resistance genes and mobile genetic elements by microplastic biofilms

Microplastics (MPs) are emerging ubiquitous pollutants in aquatic environment and have received extensive global attention. In addition to the traditional studies related to the toxicity of MPs and their carrier effects, their unique surface-induced biofilm formation also increases the ecotoxicity potential of MPs from multiple perspectives. In this review, the ecological risks of MPs biofilms were summarized and assessed in detail from several aspects, including the formation and factors affecting the development of MPs biofilms, the selective enrichment and propagation mechanisms of current pollution status of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) in MPs biofilms, the dominant bacterial communities in MPs biofilms, as well as the potential risks of ARGs and MGEs transferring from MPs biofilms to aquatic organisms. On this basis, this paper also put forward the inadequacy and prospects of the current research and revealed that the MGEs-mediated ARG propagation on MPs under actual environmental conditions and the ecological risk of the transmission of ARGs and MGEs to aquatic organisms and human beings are hot spots for future research. Relevant research from the perspective of MPs biofilm should be carried out as soon as possible to provide support for the ecological pollution prevention and control of MPs.

Effects of erythromycin on biofilm formation and resistance mutation of Escherichia coli on pristine and UV-aged polystyrene microplastics

Microplastics (MPs) and antibiotics co-occur widely in the environment and pose combined risk to microbial communities. The present study investigated the effects of erythromycin on biofilm formation and resistance mutation of a model bacterium, E. coli, on the surface of pristine and UV-aged polystyrene (PS) MPs sized 1-2 mm. The properties of UV-aged PS were significantly altered compared to pristine PS, with notable increases in specific surface area, carbonyl index, hydrophilicity, and hydroxyl radical content. Importantly, the adsorption capacity of UV-aged PS towards erythromycin was approximately 8-fold higher than that of pristine PS. Biofilms colonizing on UV-aged PS had a greater cell count (5.6 × 108 CFU mg-1) and a higher frequency of resistance mutation (1.0 × 10-7) than those on pristine PS (1.4 × 108 CFU mg-1 and 1.4 × 10-8, respectively). Moreover, erythromycin at 0.1 and 1.0 mg L-1 significantly (p < 0.05) promoted the formation and resistance mutation of biofilm on both pristine and UV-aged PS. DNA sequencing results confirmed that the biofilm resistance was attributed to point mutations in rpoB segment of the bacterial genome. qPCR results demonstrated that both UV aging and erythromycin repressed the expression levels of a global regulator rpoS in biofilm bacteria, as well as two DNA mismatch repair genes mutS and uvrD, which was likely to contribute to increased resistance mutation frequency.

An overview of the occurrence, impact of process parameters, and the fate of antibiotic resistance genes during anaerobic digestion processes

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.

Microplastics as carriers of antibiotic resistance genes and pathogens in municipal solid waste (MSW) landfill leachate and soil: a review

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.

Graphical Abstract

Occurrence, distribution and sources of microplastics in typical marine recirculating aquaculture system (RAS) in China: The critical role of RAS operating time and microfilter

Industrial mariculture, a vital means of providing high quality protein to humans, is a potential source of microplastics (MPs) which have recently received increasing attention. This study investigated the occurrence and distribution of microplastics in feed, source water and recirculating aquaculture system (RAS) with long & short operating times as well as in fish from typical industrial mariculture farms in China. Results showed that microplastics occurred in all samples with the average concentration of 3.53 ± 1.39 particles/g, 0.70 ± 0.17 particles/L, 1.53 ± 0.21 particles/L and 2.21 ± 0.62 particles/individual for feed, source water, RAS and fish, respectively. Microplastics were mainly fiber in shape, blue in color and 20-500 μm in size. Compared with short operated RAS, long operating time led to higher microplastic concentration in RAS, especially that of microplastic in 20-500 μm, granular and blue. Regardless of short or long operating time, microplastics in RAS mainly gathered in culture tank, tank before microfilter and fixed-bed biological filter, and the microfilter removed efficiently the microplastic with the shape of film, granule, fragment as well as those with size > 1000 μm. As for the polymer types, polyamide (PA, 71.9 %) and polyethylene terephthalate (PET, 65.7 %) dominated in feed and source water, respectively, which may be the reason for the high proportion of PA (38.8 % and 26.4 %) and PET (31.8 % and 30.2 %) in RAS and fish. In addition, polypropylene (PP) was also detected in RAS (18.7 %) and fish (22.6 %), indicating that other plastic facilities such as PP brush carrier also made a contribution. Positive matrix factorization (PMF) model revealed three sources of MP in RAS, namely plastic facilities, industrial sewage and plastic packaging products. Our results provided a theoretical basis for the management of MP in RAS.

Exploring the dynamics of antibiotic resistome on plastic debris traveling from the river to the sea along a representative estuary based on field sequential transfer incubations

The environmental risks arising from ubiquitous microplastics or plastic debris (PD) acting as carriers of antibiotic resistance genes (ARGs) have attracted widespread attention. Enormous amounts of plastic waste are transported by rivers and traverse estuaries into the sea every year. However, changes in the antibiotic resistome within the plastisphere (the biofilms formed on PD) as PD travels through estuaries are largely unknown. In this study, we performed sequential migration incubations for PD along Haihe Estuary to simulate the natural process of PD floating from rivers to the ocean. Metagenomic sequencing and analysis techniques were used to track microbial communities and antibiotic resistome on migrating PD and in seawater representing the marine environment. The total relative gene copies of ARGs on traveling PD remained stable. As migration between greatly varied waters, additional ARG subtypes were recruited to the plastisphere. Above 80 % ARG subtypes identified in the plastisphere were persistent throughout the migration, and over 30 % of these persistent ARGs were undetected in seawater. The bacterial hosts composition of ARGs on PD progressively altered as transported downstream. Human pathogenic bacteria carrying ARGs (HPBs-ARG) exhibited decreasing trends in abundance and species number during transfer. Individual HPBs-ARG persisted on transferred PD and were absent in seawater samples, comprising Enterobacter cloacae, Klebsiella pneumoniae, Mycobacterium tuberculosis, and Vibrio parahaemolyticus. Based on all detected ARGs and HPBs-ARG, the Projection Pursuit model was applied to synthetically evaluate the potential risks of antibiotic resistance on migrating PD. Diminished risks on PD were observed upon the river-to-sea journey but consistently remained significantly higher than in seawater. The potential risks posed to marine environments by drifting PD as dispersal vectors for antibiotic resistance deserve greater attention. Our results provide initial insights into the dynamics or stability of antibiotic resistome on PD crossing distinct aquatic systems in field estuaries.

Biofilm enhances the interactive effects of microplastics and oxytetracycline on zebrafish intestine

The enhanced adsorption of pollutants on biofilm-developed microplastics has been proved in many studies, but the ecotoxicological effects of biofilm-developed microplastics on organisms are still unclear. In this study, adult zebrafish were exposed to original microplastics, biofilm-developed microplastics, original microplastics absorbed with oxytetracycline (OTC), and biofilm-developed microplastics absorbed with OTC for 30 days. The intestinal histological damage, intestinal biomarker response, gut microbiome and antibiotic resistance genes (ARGs) profile of zebrafish were measured to explore the roles of biofilm in the effects of microplastics. The results showed that biofilm-developed microplastics significantly increased the number of goblet cells in intestinal epithelium compared with the control group. The biofilm-developed microplastics also induced the oxidative response in the zebrafish intestines, and biofilm changed the response mode in the combined treatment with OTC. Additionally, the biofilm-developed microplastics caused intestinal microbiome dysbiosis, and induced the abundance of some pathogenic genera increasing by several times compared with the control group and the original microplastics treatments, regardless of OTC adsorption. Furthermore, the abundance of ARGs in biofilm-developed microplastics increased significantly compared with the control and the original microplastic treatments. This study emphasized the significant influence and unique role of biofilm in microplastic studies.

Emerging Issues on Antibiotic-Resistant Bacteria Colonizing Plastic Waste in Aquatic Ecosystems

Antibiotic-resistant bacteria (ARB) adhesion onto plastic substrates is a potential threat to environmental and human health. This current research investigates the prevalence of two relevant human pathogens, Staphylococcus spp. and Klebsiella spp., and their sophisticated equipment of antibiotic-resistant genes (ARGs), retrieved from plastic substrates submerged into an inland water body. The results of microbiological analysis on selective and chromogenic media revealed the presence of colonies with distinctive phenotypes, which were identified using biochemical and molecular methods. 16S rDNA sequencing and BLAST analysis confirmed the presence of Klebsiella spp., while in the case of Staphylococcus spp., 63.6% of strains were found to be members of Lysinibacillus spp., and the remaining 36.3% were identified as Exiguobacterium acetylicum. The Kirby-Bauer disc diffusion assay was performed to test the susceptibility of the isolates to nine commercially available antibiotics, while the genotypic resistant profile was determined for two genes of class 1 integrons and eighteen ARGs belonging to different classes of antibiotics. All isolated bacteria displayed a high prevalence of resistance against all tested antibiotics. These findings provide insights into the emerging risks linked to colonization by potential human opportunistic pathogens on plastic waste commonly found in aquatic ecosystems.

Microplastics and nanoplastics: Source, behavior, remediation, and multi-level environmental impact

Plastics introduced into the natural environment persist, degrade, and fragment into smaller particles due to various environmental factors. Microplastics (MPs) (ranging from 1 μm to 5 mm) and nanoplastics (NPs) (less than 1 μm) have emerged as pollutants posing a significant threat to all life forms on Earth. Easily ingested by living organisms, they lead to ongoing bioaccumulation and biomagnification. This review summarizes existing studies on the sources of MPs and NPs in various environments, highlighting their widespread presence in air, water, and soil. It primarily focuses on the sources, fate, degradation, fragmentation, transport, and ecotoxicity of MPs and NPs. The aim is to elucidate their harmful effects on marine organisms, soil biota, plants, mammals, and humans, thereby enhancing the understanding of the complex impacts of plastic particles on the environment. Additionally, this review highlights remediation technologies and global legislative and institutional measures for managing waste associated with MPs and NPs. It also shows that effectively combating plastic pollution requires the synergization of diverse management, monitoring strategies, and regulatory measures into a comprehensive policy framework.

Microplastics inhibit the growth of endosymbiotic Symbiodinium tridacnidorum by altering photosynthesis and bacterial community

Microplastics, ubiquitous anthropogenic marine pollutants, represent potential threats to coral-Symbiodiniaceae relationships in global reef ecosystems. However, the mechanism underlying the impacts of polystyrene microplastics (PS-MPs) on Symbiodiniaceae remains poorly understood. In this study, the cytological, physiological, and microbial responses of Symbiodinium tridacnidorum, a representative Symbiodiniaceae species, to varying concentrations of PS-MPs (0, 5, 50, 100, and 200 mg L-1) were investigated. The results revealed that microplastic exposure inhibited cell division, resulting in reduced cell density compared to control group. Furthermore, algal photosynthetic activity, as indicated by chlorophyll content, Fv/Fm, and net photosynthetic rate, declined with increasing microplastic concentration up to 50 mg L-1. Notably, elevated levels of microplastics (100 and 200 mg L-1) prompted a significant increase in cell size in S. tridacnidorum. Transmission electron microscopy and fluorescence microscopy indicated that hetero-aggregation was formed between high levels of PS-MPs and algal cells, ultimately causing damage to S. tridacnidorum. Moreover, the impact of PS-MPs exposure on the bacterial community associated with S. tridacnidorum was investigated. The results showed a reduction in alpha diversity of the bacterial community in groups exposed to 50, 100, and 200 mg L-1 of microplastics compared to those treated with 0 and 5 mg L-1. Additionally, the relative abundance of Marinobacter, Marivita, and Filomicrobium significantly increased, while Algiphilus and norank Nannocystaceae declined after microplastic exposure. These findings suggest that MPs can inhibit the growth of S. tridacnidorum and alter the associated bacterial community, posing a potential serious threat to coral symbiosis involving S. tridacnidorum.

Potential synergy of microplastics and nitrogen enrichment on plant holobionts in wetland ecosystems

Wetland ecosystems are global hotspots for environmental contaminants, including microplastics (MPs) and nutrients such as nitrogen (N) and phosphorus (P). While MP and nutrient effects on host plants and their associated microbial communities at the individual level have been studied, their synergistic effects on a plant holobiont (i.e., a plant host plus its microbiota, such as bacteria and fungi) in wetland ecosystems are nearly unknown. As an ecological entity, plant holobionts play pivotal roles in biological nitrogen fixation, promote plant resilience and defense chemistry against pathogens, and enhance biogeochemical processes. We summarize evidence based on recent literature to elaborate on the potential synergy of MPs and nutrient enrichment on plant holobionts in wetland ecosystems. We provide a conceptual framework to explain the interplay of MPs, nutrients, and plant holobionts and discuss major pathways of MPs and nutrients into the wetland milieu. Moreover, we highlight the ecological consequences of loss of plant holobionts in wetland ecosystems and conclude with recommendations for pending questions that warrant urgent research. We found that nutrient enrichment promotes the recruitment of MPs-degraded microorganisms and accelerates microbially mediated degradation of MPs, modifying their distribution and toxicity impacts on plant holobionts in wetland ecosystems. Moreover, a loss of wetland plant holobionts via long-term MP-nutrient interactions may likely exacerbate the disruption of wetland ecosystems' capacity to offer nature-based solutions for climate change mitigation through soil organic C sequestration. In conclusion, MP and nutrient enrichment interactions represent a severe ecological risk that can disorganize plant holobionts and their taxonomic roles, leading to dysbiosis (i.e., the disintegration of a stable plant microbiome) and diminishing wetland ecosystems' integrity and multifunctionality.

Effects of heavy metal and disinfectant on antibiotic resistance genes and virulence factor genes in the plastisphere from diverse soil ecosystems

Antibiotic-resistance genes (ARGs) are world-wide contaminants posing potential health risks. Quaternary ammonium compounds (QACs) and heavy metals can apply selective pressure on antibiotic resistance. However, there is a lack of evidence regarding their coupled effect on changes in ARGs and virulence factor genes (VFGs) in various soil types and their plastispheres. Herein, we conducted a microcosm experiment to explore the abundances and profiles of ARGs and VFGs in soil plastispheres from three distinct types of soils amended with Cu and disinfectants. The plastispheres enriched the ARGs' abundance compared to soils and stimulated the coupling effect of combined pollutants on promoting the abundances of ARGs and VFGs. Horizontal gene transfer inevitably accelerates the propagation of ARGs and VFGs in plastispheres under pollutant stress. In plastispheres, combined exposure to disinfectants and Cu increased some potential pathogens' relative abundances. Moreover, the combined effect of disinfectants and Cu on ARGs and VFGs changed with soil type in plastispheres, emphasising the necessity to incorporate soil type considerations into health risk assessments for ARGs and VFGs. Overall, this study highlights the high health risks of ARGs under the selective pressure of combined pollutants in plastispheres and provides valuable insights for future risk assessments related to antibiotic resistance.

Marine plastisphere selectively enriches microbial assemblages and antibiotic resistance genes during long-term cultivation periods

Several studies have focused on identifying and quantifying suspended plastics in surface and subsurface seawater. Microplastics (MPs) have attracted attention as carriers of antibiotic resistance genes (ARGs) in the marine environment. Plastispheres, specific biofilms on MP, can provide an ideal niche to spread more widely through horizontal gene transfer (HGT), thereby increasing risks to ecosystems and human health. However, the microbial communities formed on different plastic types and ARG abundances during exposure time in natural marine environments remain unclear. Four types of commonly used MPs (polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC)) were periodically cultured (46, 63, and 102 d) in a field-based marine environment to study the co-selection of ARGs and microbial communities in marine plastispheres. After the first 63 d of incubation (p < 0.05), the initial 16S rRNA gene abundance of microorganisms in the plastisphere increased significantly, and the biomass subsequently decreased. These results suggest that MPs can serve as vehicles for various microorganisms to travel to different environments and eventually provide a niche for a variety of microorganisms. Additionally, the qPCR results showed that MPs selectively enriched ARGs. In particular, tetA, tetQ, sul1, and qnrS were selectively enriched in the PVC-MPs. The abundances of intl1, a mobile genetic element, was measured in all MP types for 46 d (5.22 × 10-5 ± 8.21 × 10-6 copies/16s rRNA gene copies), 63 d (5.90 × 10-5 ± 2.49 × 10-6 copies/16s rRNA gene copies), and 102 d (4.00 × 10-5 ± 5.11 × 10-6 copies/16s rRNA gene copies). Network analysis indicated that ARG profiles co-occurred with key biofilm-forming bacteria. This study suggests that the selection of ARGs and their co-occurring bacteria in MPs could potentially accelerate their transmission through HGT in natural marine plastics.

Beach sand plastispheres are hotspots for antibiotic resistance genes and potentially pathogenic bacteria even in beaches with good water quality

Massive amounts of microplastics are transported daily from the oceans and rivers onto beaches. The ocean plastisphere is a hotspot and a vector for antibiotic resistance genes (ARGs) and potentially pathogenic bacteria. However, very little is known about the plastisphere in beach sand. Thus, to describe whether the microplastics from beach sand represent a risk to human health, we evaluated the bacteriome and abundance of ARGs on microplastic and sand sampled at the drift line and supralittoral zones of four beaches of poor and good water quality. The bacteriome was evaluated by sequencing of 16S rRNA gene, and the ARGs and bacterial abundances were evaluated by high-throughput real-time PCR. The results revealed that the microplastic harbored a bacterial community that is more abundant and distinct from that of beach sand, as well as a greater abundance of potential human and marine pathogens, especially the microplastics deposited closer to seawater. Microplastics also harbored a greater number and abundance of ARGs. All antibiotic classes evaluated were found in the microplastic samples, but not in the beach sand ones. Additionally, 16 ARGs were found on the microplastic alone, including genes related to multidrug resistance (blaKPC, blaCTX-M, tetM, mdtE and acrB_1), genes that have the potential to rapidly and horizontally spread (blaKPC, blaCTX-M, and tetM), and the gene that confers resistance to antibiotics that are typically regarded as the ultimate line of defense against severe multi-resistant bacterial infections (blaKPC). Lastly, microplastic harbored a similar bacterial community and ARGs regardless of beach water quality. Our findings suggest that the accumulation of microplastics in beach sand worldwide may constitute a potential threat to human health, even in beaches where the water quality is deemed satisfactory. This phenomenon may facilitate the emergence and dissemination of bacteria that are resistant to multiple drugs.

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.

Microplastics as carriers of toxic pollutants: Source, transport, and toxicological effects

Microplastic pollution has emerged as a new environmental concern due to our reliance on plastic. Recent years have seen an upward trend in scholarly interest in the topic of microplastics carrying contaminants; however, the available review studies have largely focused on specific aspects of this issue, such as sorption, transport, and toxicological effects. Consequently, this review synthesizes the state-of-the-art knowledge on these topics by presenting key findings to guide better policy action toward microplastic management. Microplastics have been reported to absorb pollutants such as persistent organic pollutants, heavy metals, and antibiotics, leading to their bioaccumulation in marine and terrestrial ecosystems. Hydrophobic interactions are found to be the predominant sorption mechanism, especially for organic pollutants, although electrostatic forces, van der Waals forces, hydrogen bonding, and pi-pi interactions are also noteworthy. This review reveals that physicochemical properties of microplastics, such as size, structure, and functional groups, and environmental compartment properties, such as pH, temperature, and salinity, influence the sorption of pollutants by microplastic. It has been found that microplastics influence the growth and metabolism of organisms. Inadequate methods for collection and analysis of environmental samples, lack of replication of real-world settings in laboratories, and a lack of understanding of the sorption mechanism and toxicity of microplastics impede current microplastic research. Therefore, future research should focus on filling in these knowledge gaps.