Characterization of Microplastic-Associated Biofilm Development along a Freshwater-Estuarine Gradient

Bipartite trophic levels cannot resist the interference of microplastics: A case study of submerged macrophytes and snail

Some studies frequently focus on the toxic effects of compound pollution formed by microplastics and other pollutants on individual organisms, but it is still unclear how multi-trophic level organisms in compound communities resist the stress of microplastics. Thus, this research used a dose-response experiment (0, 0.1, 0.2, 0.5, 1 mg L-1) to illustrate the influences that microplastics might have on two symbiotic freshwater organisms Vallisneria natans and Sinotaia quadrata. The results showed the reduction of V. natans biomass in 0.5 and 1 mg L-1 groups (28-38 %), and disturbances on the photosynthetic system, reduced the chlorophyll content (15-85 %) and maximum quantum yields (10-31 %). In the case of S. quadrata, which subsisted by scraping leaf biofilms, there was a disruption in the functioning of the antioxidant system. Concurrently, the activities of digestive and neurotransmitter enzymes were affected, potentially leading to detrimental impacts on the organism's essential physiological processes. The introduction of microplastics significantly enhanced the relative abundance of specific microbial taxa, such as Proteobacteria within the biofilm of V. natans leaves and chloroflexi in the rhizosphere, thereby altering the microbial community assembly process. This means the potential ecological functions with microbes as the carrier was influenced. These results indicated that microplastic in aquatic environments can impact the metabolism, autotrophic, and heterotrophic behavior of double-end trophic organisms through symbiotic activities. Therefore, our study reveals how polystyrene microplastics affect the growth of submerged aquatic plants and snails, and from the perspective of community integrity and health, the introduction of these pollutants into freshwater environments may cause disruptive effects.

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.

Characteristics of microplastics in typical poultry farms and the association of environment microplastics colonized-microbiota, waterfowl gut microbiota, and antibiotic resistance genes

Microplastics (MPs) pollution is a growing global environmental concern. MPs serve as ecological niches for microbial communities, which may accelerate the spread of antibiotic resistance genes (ARGs), posing risks to the breeding industry. While studies on MPs in aquatic organisms are common, research on farmed poultry is limited. This study investigates MPs in poultry farm environments and waterfowl intestines for the first time. MPs were isolated via density separation and analyzed for characterization in soil, pond water, and waterfowl intestines. Metagenomics was used to investigate the association between environment MPs colonized-microbiota and waterfowl gut microbiota. Our findings reveal that MPs are abundant in soil (6.75 ± 2.78 items/g d.w.), pond water (0.94 ± 0.28 items/g w.w.), and poultry intestines (45.35 ± 19.52 items/g w.w.), primarily appearing as fragmented particles sized 20-50 μm. MPs abundance in intestines correlates with environmental levels. Colonized-microbiota on MPs are linked to poultry intestinal microbiota, with greater diversity and microbial functions. Network analysis reveals that Corynebacterium plays a key role in MPs and poultry intestinal. Polymyxin resistance exhibits high clustering. Procrustes analysis reveals correlations between MPs, bacteria, and ARGs in the farming environment. Overall, MPs in poultry farms may facilitate pathogen and ARGs transmission, posing risks to animal gut health.

Natural Dynamics: Fresh Insight into the Succession of Microplastic-Borne Bacterial Communities along Riverine Courses to the Ocean

Microplastics (MPs) transport bacteria from rivers to oceans, impacting aquatic ecosystems. In situ incubation, a common method for studying bacterial communities on MPs, cannot reproduce complex and realistic environmental dynamics. Herein, a natural incubation experiment was performed to reproduce the migration of nine different substrates from rivers to the sea and examine the succession of bacterial communities on their surfaces. Furthermore, an in situ sequential incubation experiment and the natural incubation experiment were compared. Substantial structural changes were observed in the bacterial communities on MPs along riverine courses to the ocean, with implications for biosecurity, elemental cycling, and degradation potential in aquatic ecosystems. Rapid fluctuations in salinity were the prevalent factor for the significant changes in the bacterial community on MPs. The type of substrate has a significant effect on the formation and structure of bacterial communities, which depend on substrate structure and composition. Unlike in situ incubation, natural incubation reproduces realistic environmental dynamics, providing more comprehensive information on bacterial species composition, diversity, functional metabolism, and structure on MPs. This study introduces a novel methodological approach for MP research and enhances our understanding of the ecological risks associated with MPs transported from rivers to the ocean.

Microbial degradation potential of microplastics in urban river sediments: Assessing and predicting the enrichment of PE/PP-degrading bacteria using SourceTracker and machine learning

Microplastic mitigation strategies that adapt to various actual aquatic environments require the ability to predict their microbial degradation potential. However, the sources and enrichment characteristics of the degrading bacteria in the plastisphere from river sediments, and their relationship with environmental conditions remain poorly understood. Here, SourceTracker analysis was adopted to investigate the sources and distribution characteristics of total PE/PP-degrading bacteria (TD) and local PE/PP-degrading bacteria (LD) in the plastisphere and surrounding sediments of the urban river. To better characterize the enrichment property of PE/PP-degrading bacteria in the plastisphere, two specific indices, the enrichment ratios of TD (ERTD) and LD (ERLD) separately, were first defined in this study. Furthermore, machine learning models were constructed to predict these enrichment ratios. The results showed that river sediments represented an important reservoir of PE/PP-degrading bacteria within the plastisphere (representing 81.8 %). Both the enrichment ratio of TD (R2 = 0.720) and the enrichment ratio of LD (R2 = 0.537) showed a significant positive correlation with the carbonyl index of PE/PP, indicating that the enrichment ratios can effectively reflect the microbial degradation potential of PE/PP in sediments. Compared to gradient boosting regression tree, multilayer perceptron, and support vector machines, the random forest (RF) model demonstrated superior accuracy in predicting both the enrichment ratio of TD (R2Test = 0.954, MSE = 0.180) and the enrichment ratio of LD (R2Test = 0.924, MSE = 0.009. It was also observed that the enrichment ratios were higher in river bends, indicating that river bends were potential hot zones for microbial degradation of PE/PP. SHAP analysis highlighted that the key environmental factors exhibited synergistic effects on both enrichment ratios of TD and LD. Finally, the concentration range of key environmental factors that maximize the enrichment ratio was determined. This study constitutes a powerful example of predicting microplastic microbial degradation potential across various scientific disciplines and provides a basis for the effective management of microplastics.

Non-degradable microplastic promote microbial colonization: A meta-analysis comparing the effects of microplastic properties and environmental factors

Microplastics serve as favorable substrates for microbial colonization, promoting biofilm formation, which consequently facilitates the accumulation of pollutants and aids in the degradation of microplastics. Hence, obtaining a thorough comprehension of the factors that influence the development of microplastic biofilms is imperative. Nevertheless, there have been conflicting responses concerning biofilm formation in conjunction with microplastic characteristics and environmental conditions. As a result, a meta-analysis was conducted to quantitatively evaluate the impact of microplastic properties and environmental factors on biofilm formation. The findings indicated that the type and size of microplastics significantly influence biofilm growth on their surfaces. Non-degradable microplastics, particularly polyvinyl chloride (PVC) and polystyrene (PS), exhibited higher surface biomass and biodiversity in microplastic-attached biofilms compared to degradable microplastics. Furthermore, it was observed that smaller microplastics were more conducive to microbial colonization. Model selection and correlation analysis further indicated that the environment acts as a substantial predictor of biofilm formation, with prolonged exposure significantly enhancing microbial diversity within biofilms as opposed to short-term exposure. Moreover, meta-regression analysis illustrated a positive correlation between biofilm biomass and alpha-diversity with temperature, while salinity exhibited a negative correlation in diverse aquatic settings. Notably, the ease of biofilm formation on microplastics was observed to be greater in oceans compared to lakes, yet biofilms exhibited a higher diversity increment in lakes than their oceanic counterparts. In the long-term growth of biofilms, initial biomass and diversity are influenced by microplastic characteristics and the surrounding environment, although environmental influences may assume more significance as time progresses.

Changes in electron distribution of aged microplastic and their environmental impacts in aquatic environments

Microplastics (MPs) are widespread environmental pollutants. This study primarily examines the changes in electro distribution of aged MPs in aquatic environments and their subsequent impact on the environment. Under the action of natural and artificial aging, the electron cloud arrangement of MPs will change, thus affecting the relevant properties of MPs. Among them, the free radicals formed by advanced oxidation technology will be enriched on the surface of MPs carrying benzene rings, and react with other pollutants (organic pollutants, heavy metals, etc.) adsorbed by MPs to form environmental persistent free radicals (EPFRs). The electron cloud density of MPs carrying EPFRs increases, and the reactivity will also increase. Additionally, the oxygen-containing functional groups on the surface of aged MPs enhance their selective adsorption, altering their environmental impact. MPs can serve as a source of free radicals in the environment, enhance the oxidation capacity of other substances in the environment, and even affect the expression of antibiotic resistance genes. In addition, MPs have a high mobility, which will have a greater negative impact in the environment. Additionally, the high mobility of MPs amplifies their negative environmental impact. This study examines the changes in electron distribution of aged MPs and highlights their effects on aquatic ecosystems, providing insights into pollution control, toxicity, and degradation mechanisms.

Microbial composition on microplastics mediated by stream impairment

BACKGROUND

Studies into biofilm interactions with microplastic polymers in marine environments are widespread in the literature. Increasing evidence suggests that lotic microplastics are a significant contributor and may accumulate harmful or pathogenic organisms, thereby contributing to the degradation of marine ecosystems where they meet riverine systems. Suboptimal water quality of these riverine systems may influence these biomes. This project compared the microbial diversity of biofilms that developed on microplastics to natural stone substrates in an impaired and unimpaired section of the Quinnipiac River Watershed. In this project, the influence of impairment was studied based on microbial diversity via 16S rRNA gene sequencing while monitoring total colony and fecal coliform colony counts using standard water sampling methods.

RESULTS

Total coliform colony counts were greater in the impaired Quinnipiac River site than in the unimpaired Honeypot Brook tributary and on the microplastic substrate than the stone substrate. Sequenced features to the class level were dominated by Alphaproteobacteria, Betaproteobacteria, and Gammaproteobacteria, comprising 75% of the community biome. Simpson's Diversity indices indicated that within the two substrates, there was little variation between the communities. However, it was noted that microplastic alpha diversity trended slightly lower than the stone. Further analysis of common aquatic enteropathogens showed that the genus Citrobacter was significantly more abundant on the microplastics at both locations.

CONCLUSIONS

Our results indicate impaired waterbodies with a microplastic burden may retain greater fecal coliform bacterial loads than unimpaired waterbodies. Increased microplastic loads in compromised lotic systems may have an additive impact. Water quality remediation and careful monitoring are recommended to reduce this effect. Comparing this study with environmental community analysis could provide valuable insight into preferential surface attachment of bacteria onto microplastic.

Environmental Health and Safety Implications of the Interplay Between Microplastics and the Residing Biofilm

The increasing prevalence of microplastics in the environment has raised concerns about their potential environmental and health implications. Biofilms readily colonize microplastics upon their entry into the environment, altering their surface characteristics. While most studies have explored how biofilms influence the adsorption and transportation of other contaminants by microplastics, the reciprocal interplay between microplastics and biofilms and the resulting ecological risks remain understudied. This review comprehensively reviews the impact of microplastic properties on biofilm formation and composition, including the microbial community structure. We then explore the dynamic interactions between microplastics and biofilms, examining how biofilms alter the physicochemical properties, migration, and deposition of microplastics. Furthermore, we emphasize the potential of biofilm-colonized microplastics to influence the environmental fate of other pollutants. Lastly, we discuss how biofilm-microplastic interactions may modify the bioavailability, biotoxicity, and potential health implications of microplastics.

"Tire plastisphere" in aquatic ecosystems: Biofilms colonizing on tire particles exhibiting a distinct community structure and assembly compared to conventional plastisphere

Tire particles (TPs) significantly contribute to microplastics in aquatic ecosystems, which has recently attracted ecological concerns worldwide. Numerous studies have shown that biofilms on microplastics harbor unique species and harmful functions, but it remains unclear whether TPs could offer distinct niches for biofilms compared to conventional microplastics (CP). This study investigated the succession and assembly of biofilms on TPs compared with CP over 60 days. Our results showed the community structures of biofilms on TPs and CP were distinct. Intriguingly, a greater structural dissimilarity was observed between TPs-associated communities and natural biofilms compared to that between CP-associated communities and natural biofilms. This dissimilarity became more pronounced as biofilms progressed through succession. Furthermore, the bacterial community on the TPs exhibits a network of greater complexity, more stable structure, and higher activity than that on the CP, but the pattern was reversed in the eukaryotic community. Deterministic processes had a more critical impact on bacterial communities on TPs, whereas distinct stochastic processes controlled eukaryotic communities on TPs (dispersal limitation) and CP (undominated processes). Altogether, this study tentatively introduced the term "tire plastisphere" (i.e., TP-attached biofilms), emphasizing TPs could serve as more artificial microbial habitats and pose potential risks in disturbing aquatic ecology.

Physicochemical behavior and ecological risk of biofilm-mediated microplastics in aquatic environments

The prevalence of microplastics (MPs) in aquatic environments has become the core of environmental pollution. In recent years, the inevitable biological aging process of MPs in natural environments has attracted researchers' attention. Such biofilm-mediated MPs, colonized by microorganisms, affect the physicochemical behavior and potential ecological risks of MPs. Therefore, it is critical to understand the impact of MPs' biofilm formation on the environmental fate and toxicity of MPs. This review presented a comprehensive discussion of the impact of biofilm formation on unique carrier effects and toxicological effects of MPs in aquatic environments. First, the biofilm formation process on MPs, the compositions of microorganisms in biofilm and the factors influencing biofilm formation were briefly summarized. Second, the sorption of pollutants and enrichment of antibiotic resistance genes onto biofilm-mediated MPs were discussed. Third, the potential effects of biofilm-mediated MPs on gut microbiota were analyzed. Finally, gaps in the field that require further investigations were put forward. This review emphasized that biofilm-mediated MPs have higher environmental risks and ecotoxicity, which is helpful in providing new insights for pollution prevention and control of new pollutant MPs.

When plastisphere and drilosphere meet: Earthworms facilitate microbiome and nutrient turnover to accelerate biodegradation of agricultural plastic films

Agricultural plastic mulching films have been an environmental concern for decades. The effects of the interactions between the anthropogenic plastisphere and other soil biospheres, particularly that of earthworms, on the fate of plastics remain poorly understood. Here, we investigated the decomposition of buried nonbiodegradable low-density polyethylene (LDPE) versus biodegradable PBTA/PLA copolymers in the presence of earthworms (Amynthas cortices) in dynamic microcosms. Earthworms significantly enhanced the biodegradation of plastic films in situ, as confirmed by mass reduction, surface modification, and changes in the molecular weights of films. Notably, the PBTA/PLA films exhibited a 1.41-fold increase in mass loss and a 5.69% reduction in the number-average molecular weight when incubated with earthworms. Earthworms influenced the microbial assembly within the plastisphere by increasing both bacterial and fungal biodiversity, as well as their network complexity. The time-decay patterns in the abundance of keystone degrader taxa, including the genera Noviherbaspirillum, Rhizobacter, and Mortierella, were mitigated by earthworms over the 60-day period. Additionally, earthworms preferentially consumed recalcitrant dissolved organic matter in LDPE and PBAT/PLA plastisphere soils, thereby increasing the bioavailability of components that serve as nutrient supplies for plastisphere microbiomes. Our findings demonstrate that earthworms enhance the decomposition of plastics in soils via cross-species interplay within the plastisphere and drilosphere, contributing not only to soil conditioning and biodiversity but also to plastic biodegradation in natural agroecosystems.

Selective enrichment of high-risk antibiotic resistance genes and priority pathogens in freshwater plastisphere: Unique role of biodegradable microplastics

Microplastics (MPs) has been concerned as emerging vectors for spreading antibiotic resistance and pathogenicity in aquatic environments, but the role of biodegradable MPs remains largely unknown. Herein, field in-situ incubation method combined with metagenomic sequencing were employed to reveal the dispersal characteristics of microbial community, antibiotic resistance genes (ARGs), mobile genetic elements (MGEs), and virulence factors (VFs) enriched by MPs biofilms. Results showed that planktonic microbes were more prone to enrich on biodegradable MPs (i.e., polyhydroxyalkanoate and polylactic acid) than non-biodegradable MPs (i.e., polystyrene, polypropylene and polyethylene). Distinctive microbial communities were assembled on biodegradable MPs, and the abundances of ARGs, MGEs, and VFs on biofilms of biodegradable MPs were much higher than that of non-biodegradable MPs. Notably, network analysis showed that the biodegradable MPs selectively enriched pathogens carrying ARGs, VFs and MGEs concurrently, suggesting a strong potential risks of co-spreading antibiotic resistance and pathogenicity through horizontal gene transfer. According to WHO priority list of Antibiotic Resistant Pathogens (ARPs) and ARGs health risk assessment framework, the highest abundances of Priority 1 ARPs and Rank I risk ARGs were found on polylactic acid and polyhydroxyalkanoate, respectively. These findings elucidate the unique and critical role of biodegradable MPs for selective enrichment of high-risk ARGs and priority pathogens in freshwater environments.

Revivable self-assembled supramolecular biomass fibrous framework for efficient microplastic removal

Microplastic remediation in aquatic bodies is essential for the entire ecosystem, but is challenging to achieve with a universal and efficient strategy. Here, we developed a sustainable and environmentally adaptable adsorbent through supramolecular self-assembly of chitin and cellulose. This biomass fibrous framework (Ct-Cel) showcases an excellent adsorption performance for polystyrene, polymethyl methacrylate, polypropylene, and polyethylene terephthalate. The affinity for diverse microplastics is attributed to the transformation of multiple intermolecular interactions between different microplastics and Ct-Cel. Meanwhile, the strong resistance of Ct-Cel to multiple pollutants in water enables an enhanced adsorption when coexisting with microorganisms and Pb2+. Moreover, Ct-Cel can remove 98.0 to 99.9% of microplastics in four types of real water and maintains a high removal efficiency of up to 95.1 to 98.1% after five adsorption cycles. This work may open up prospects for functional biomass materials for cost-efficient remediation of microplastics in complex aquatic environments.

Microplastics distribution, ecological risk and outflows of rivers in the Bohai Rim region of China - A flux model considering small and medium-sized rivers

Microplastics (MPs) pollution and its ecological risks have attracted increasing global attention. The Bohai Rim region (BRR), as the economic and population center of the entire northern China, still lacks a precise assessment of MPs pollution. Although current attention on MPs pollution mainly focuses on large rivers, small and medium-sized rivers are more numerous and more closely connected to human activities. In this study, measurement data of MPs from 11 estuaries in the BRR was collected to understand MPs distribution and ecological risk. The results indicate that the overall MPs pollution in these estuaries is still at a low level, with an average abundance of 1254.3 particles m-3. While the pollution load index (1.85) is relatively low, the potential ecological risk of PVC in some area (S8, EPVC = 1433.78, III) warrants further attention. Then we integrated data from 22 relevant rivers (covering all size rivers) in this region from the literature to fit a MPs flux model and assessed the MPs outflow from the four provinces and cities in the region. A strong correlation is achieved between modeled estimates and field measurements (r2 = 0.74), which can well estimate the river MPs outflows in northern China such as the Nanfei River. The MPs outflow from the four provinces (cities) is calculated to be 123.235 (range 44.415-242.314) T year-1, of which Shandong accounted for >80 % (104.066 T year-1). The small and medium-sized rivers accounted for 47 % (58.08 T year-1), whose contribution to MPs outflows should not be underestimated. This study can help us to accurately assess MPs pollution in different coastal areas in northern China, benefiting the formulation of precise control measures and policies for marine MPs pollution.

Microplastics-biofilm interactions in biofilm-based wastewater treatment processes: A review

Microplastics, pervasive contaminants from plastic, present significant challenges to wastewater treatment processes. This review critically examines the interactions between microplastics and biofilm-based treatment technologies, specifically focusing on the concepts of "biofilm on microplastics" and "microplastics in biofilm". It discusses the implications of these interactions in contaminant removal and process performance. Advanced characterization techniques, including morphological characterization, chemical composition analysis, and bio-information analysis, are assessed to elucidate the complex interplay between microplastics and biofilms within biofilters, biological aerated filters (BAFs), rotating biological contactors (RBCs), and moving bed biofilm reactors (MBBRs). This review synthesizes current research findings, highlighting that microplastics can either hinder or enhance the treatment processes, contingent on their concentration, physicochemical properties, and the specific biofilm technology employed. The insights gained from this review are essential for developing strategies to mitigate the adverse effects of microplastics and for optimizing the design and operation of wastewater treatment.

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.

Eco-environmental responses of Eichhornia crassipes rhizobacteria community to co-stress of per(poly)fluoroalkyl substances and microplastics

The stabilization of rhizobacteria communities plays a crucial role in sustaining healthy macrophyte growth. In light of increasing evidence of combined pollution from microplastics (MPs) and per- and polyfluoroalkyl substances (PFASs), Selecting typical floating macrophyte as a case, this study explored their impacts using hydroponic simulations and 16S rRNA high-throughput sequencing. A total of 31 phyla, 77 classes, 172 orders, 237 families, 332 genera, and 125 rhizobacteria species were identified. Proteobacteria (16.19% to 57.70%) was the dominant phylum, followed by Bacteroidota (12.34% to 44.48%) and Firmicutes (11.31% to 36.36%). In terms of α-diversity, polystyrene (PS) MPs and PFASs significantly impacted community abundance (ACE and PD-tree) rather than evenness (Shannon and Pielou) compared to the control. βMNTD and βNTI analyses revealed that PS MPs enhanced deterministic assembly processes driven by F-53B and GenX, while mitigating those induced by PFOA and PFOS. Contamination treatments narrowed the ecological niche breadths at both the phylum (5% (PS) to 49.91% (PS & PFOA)) and genus levels (8% (PS) to 63.96% (PS & PFOA)). Functionally, MPs and PFASs decreased the anaerobic capacity and ammonia nitrogen utilization of rhizosphere bacteria. This study enhances our understanding of the microecological responses of macrophyte-associated bacteria to combined MP and PFAS contamination and offers insights into ecological restoration strategies and mitigating associated environmental risks.

Toxicokinetics of microplastics in Macrobrachium nipponense and their impact on the bioavailability of loaded pollutants

Microplastics (MPs) have unique toxicokinetic (TK) processes that differ from those of soluble pollutants. This study investigated the ingestion, migration, accumulation, and clearance of environmental aging MPs in the Japanese swamp shrimp (Macrobrachium nipponense). The concentrations of plastic additives and personal care products adsorbed onto MPs in natural river water were determined, and TK models for MPs and MPs-loaded pollutants were developed. Results showed that the formation of surface biofilms and alterations in the distribution of MPs in waters caused by environmental aging affect MPs bioavailability, which is mainly related to the feeding habits of shrimp. The decrease in MPs particle size caused by biological digestion and the increase in the number of oxygen-containing functional groups caused by environmental aging affect the TK process of MPs. The TK model of MPs-loaded pollutants revealed the cleaning effect of shrimp on pollutants adsorbed onto MPs during swallowing and spitting MPs. This cleaning effect significantly increases the bioavailability of MPs-associated pollutants in aquatic environments. This study provides a new perspective for understanding the interactions between environmental MPs and their associated pollutants in aquatic ecosystems.

Evidence that microplastics at environmentally relevant concentration and size interfere with energy metabolism of microalgal community

To address two current issues in evaluating the toxicity of microplastics (MPs) namely, conflicting results due to species specificity and the ecological irrelevance of laboratory data, this study conducted a 10-day exposure experiment using a microalgal community comprising three symbiotic species. The experiment involved virgin and Benzo[a]pyrene-spiked micron-scale fibers and fragments made of polyethylene terephthalate (PET) and polypropylene (PP). The results showed that, from a physiological perspective, environmentally relevant concentrations of micron-scale MPs decreased saccharide accumulation in microalgal cells, as confirmed by ultrastructural observations. MPs may increase cellular energy consumption by obstructing cellular motility, interfering with nutrient uptake, and causing sustained oxidative stress. Additionally, MPs and adsorbed B[a]P induced DNA damage in microalgae, potentially further disrupting cellular energy metabolism. Ecologically, MPs altered the species abundance in microalgal communities, suggesting they could weaken the ecological functions of these communities as producers and affect ecosystem diversity and stability. This study marks a significant advancement from traditional single-species toxicity experiments to community-level assessments, providing essential insights for ecological risk assessment of microplastics and guiding future mechanistic studies utilizing multi-omics analysis.

Navigating the difference of riverine microplastic movement footprint into the sea: Particle properties influence

As a critical source of marine microplastics (MPs), estuarine MPs community varied in movement due to particle diversity, while tide and runoff further complicated their transport. In this study, a particle mass gradient that represents MPs in the surface layer of the Yangtze River estuary was established. This was done by calculating the masses of 16 particle types using the particle size probability density function (PDF), with typical shapes and polymers as classifiers. Further, Aschenbrenner shape factor and polymer density were embedded into drag coefficients to categorically trace MP movement footprints. Results revealed that the MPs in North Branch moved northward and the MPs in South Branch moved southeastward in a spiral oscillation until they left the model boundary under Changjiang Diluted Water front and the northward coastal currents. Low-density fibrous MPs are more likely to move into the open ocean and oscillate more than films, with a single PE fiber trajectory that reached a maximum oscillatory width of 16.7 km. Over 95 % of the PVC fiber particles settled in nearshore waters west of 122.5°E. Elucidating the aggregation and retention of different MPs types can provide more accurate environmental baseline reference for more precise MP exposure levels and risk dose of ingestion for marine organisms.

Undisclosed contribution of microbial assemblages selectively enriched by microplastics to the sulfur cycle in the large deep-water reservoir

The accumulation of microplastics in reservoirs due to river damming has drawn considerable attention due to their potential impacts on elemental biogeochemical cycling at the watershed scale. However, the effects of plastisphere communities on the sulfur cycle in the large deep-water reservoir remain poorly understood. Here, we collected microplastics and their surrounding environmental samples in the water and sediment ecosystems of Xiaowan Reservoir and found a significant spatiotemporal pattern of microplastics and sulfur distribution in this Reservoir. Based on the microbial analysis, plastic-degrading taxa (e.g., Ralstonia, Rhodococcus) involved in the sulfur cycle were enriched in the plastisphere of water and sediment, respectively. Typical thiosulfate oxidizing bacteria Limnobacter acted as keystone species in the plastisphere microbial network. Sulfate, oxidation reduction potential and organic matter drove the variations of the plastisphere. Environmental filtration significantly affected the plastisphere communities, and the deterministic process dominated the community assembly. Furthermore, predicted functional profiles related to sulfur cycling, compound degradation and membrane transport were significantly enriched in the plastisphere. Overall, our results suggest microplastics as a new microbial niche exert different effects in water and sediment environments, and provide insights into the potential impacts of the plastisphere on the sulfur biogeochemical cycle in the reservoir ecosystem.

Silver nanoparticles facilitate phage-borne resistance gene transfer in planktonic and microplastic-attached bacteria

The spread of bacteriophage-borne antibiotic resistance genes (ARGs) poses a realistic threat to human health. Nanomaterials, as important emerging pollutants, have potential impacts on ARGs dissemination in aquatic environments. However, little is known about its role in transductive transfer of ARGs mediated by bacteriophage in the presence of microplastics. Therefore, this study comprehensively investigated the influence of silver nanoparticles (AgNPs) on the transfer of bacteriophage-encoded ARGs in planktonic Escherichia coli and microplastic-attached biofilm. AgNPs exposure facilitated the phage transduction in planktonic and microplastic-attached bacteria at ambient concentration of 0.1 mg/L. Biological binding mediated by phage-specific recognition, rather than physical aggregation conducted by hydrophilicity and ζ-potential, dominated the bacterial adhesion of AgNPs. The aggregated AgNPs in turn resulted in elevated oxidative stress and membrane destabilization, which promoted the bacteriophage infection to planktonic bacteria. AgNPs exposure could disrupt colanic acid biosynthesis and then reduce the thickness of biofilm on microplastics, contributing to the transfer of phage-encoded ARGs. Moreover, the roughness of microplastics also affected the performance of AgNPs on the transductive transfer of ARGs in biofilms. This study reveals the compound risks of nanomaterials and microplastics in phage-borne ARGs dissemination and highlights the complexity in various environmental scenarios.

Effects of microplastics on the structure and function of bacterial communities in sediments of a freshwater lake

As an emerging pollutant, microplastics (MPs) cause widespread concern around the world owing to the serious threat they pose to ecosystems. In particular, sediments are thought to be the long-term sink for the continual accumulation of MPs in freshwater ecosystems. Polyethylene (PE) and polyethylene terephthalate (PET) have been frequently detected with large concentration variations in freshwater sediments from the lower reaches of the Yangtze River, one of the most economically developed regions in China, characterized by accelerated urbanization and industrialization, high population density and high plastics consumption. However, the impact of PE and PET on the sedimental bacterial community composition and its function has not been well reported for this specific region. Herein, PE and PET particles were added to freshwater sediments to assess the effects of different MP types on the bacterial community and its function, using three concentrations (500, 1500 and 2500 items/kg) per MP and incubations of 35, 105 and 175 days, respectively. This study identified a total of 68 phyla, 211 classes, 518 orders, 853 families and 1745 genera. Specifically, Proteobacteria, Chloroflexi, Acidobacteriota, Actinobacteriota and Firmicutes were the top five phyla. A higher bacterial diversity was obtained in control sediments than in the MP-treated sediments. The presence of MPs, whether PET or PE, had significant impact on the bacterial diversity, community structure and community composition. PICRUSt2 and FAPOTAX predictions demonstrated that MPs could potentially affect the metabolic pathways and ecologically functional groups of bacteria in the sediment. Besides the MP-related factors, such as the type, concentration and incubation time, the physicochemical parameters had an effect on the structure and function of the bacterial community in the freshwater sediment. Taken together, this study provides useful information for further understanding how MPs affect bacterial communities in the freshwater sediment of the lower reaches of the Yangtze River, China.

Freshwater plastisphere: a review on biodiversity, risks, and biodegradation potential with implications for the aquatic ecosystem health

The plastisphere, a unique microbial biofilm community colonizing plastic debris and microplastics (MPs) in aquatic environments, has attracted increasing attention owing to its ecological and public health implications. This review consolidates current state of knowledge on freshwater plastisphere, focussing on its biodiversity, community assembly, and interactions with environmental factors. Current biomolecular approaches revealed a variety of prokaryotic and eukaryotic taxa associated with plastic surfaces. Despite their ecological importance, the presence of potentially pathogenic bacteria and mobile genetic elements (i.e., antibiotic resistance genes) raises concerns for ecosystem and human health. However, the extent of these risks and their implications remain unclear. Advanced sequencing technologies are promising for elucidating the functions of plastisphere, particularly in plastic biodegradation processes. Overall, this review emphasizes the need for comprehensive studies to understand plastisphere dynamics in freshwater and to support effective management strategies to mitigate the impact of plastic pollution on freshwater resources.

Effects of photoaging on structure and characteristics of biofilms on microplastic in soil: Biomass and microbial community

Understanding of the environmental behaviors of microplastics is limited by a lack of knowledge about how photoaging influences biofilm formation on microplastics in soil. Here, original microplastics (OMPs) and photoaged-microplastics (AMPs) were incubated in soil to study the effect of photoaging on formation and characteristics of biofilm on the poly (butylene succinate) microplastics. Because photoaging decreased the hydrophobicity of the microplastic, the biomass of biofilm on the OMPs was nearly twice that on the AMPs in the early stage of incubation. However, the significance of the substrate on biomass in the biofilm declined as the plastisphere developed. The bacterial communities in the plastisphere were distinct from, and less diverse than, those in surrounding soil. The dominant genera in the OMPs and AMPs plastispheres were Achromobacter and Burkholderia, respectively, indicating that photoaging changed the composition of the bacterial community of biofilm at the genus level. Meantime, photoaging decreased the complexity and stability of the plastisphere bacterial community network. Results of Biolog ECO-microplate assays and functional prediction from amplicons showed that photoaging treatment enhanced the carbon metabolic capacity of the microplastic biofilm. This study provides new insights into the formation of plastispheres in soil.

Impacts of microplastic contamination on the rheology properties of sediments in a eutrophic shallow lake

Microplastic (MP) contamination is a growing global concern, with lake sediments serving as a significant sink for MP due to both anthropogenic and natural activities. Given the increasing evidence of MP accumulation in sediments, it was crucial to assess their influence on sediment erosion resistance, which directly affected sediment resuspension. To fill this gap, this study focused on the effect of MP on the sediments rheological properties. After 60-day experiments, it was found that MP addition into sediments reduced sediment viscosity, yield stress, and flow point shear stress. Meanwhile, MPs also significantly altered sediment properties and extracellular polymer composition. MP addition reduced extracellular polymeric substances production and cation exchange capacity, which then worked together and led to a weak sediment structure. Seemingly, MPs changed fluid sediment characteristics and caused stronger fluidity under less shear force. Consequently, the accumulation of MP might facilitate the resuspension of sediments under smaller wind and wave disturbances. This study provided novel insights into the direct impact of MPs on sediment physical properties using rheology, thereby enhancing our understanding of the environmental behavior of MPs in lake ecosystems.

Microbial hitchhikers on microplastics: The exchange of aquatic microbes across distinct aquatic habitats

Microplastics (MPs) have the potential to modify aquatic microbial communities and distribute microorganisms, including pathogens. This poses a potential risk to aquatic life and human health. Despite this, the fate of 'hitchhiking' microbes on MPs that traverse different aquatic habitats remains largely unknown. To address this, we conducted a 50-day microcosm experiment, manipulating estuarine conditions to study the exchange of bacteria and microeukaryotes between river, sea and plastisphere using a long-read metabarcoding approach. Our findings revealed a significant increase in bacteria on the plastisphere, including Pseudomonas, Sphingomonas, Hyphomonas, Brevundimonas, Aquabacterium and Thalassolituus, all of which are known for their pollutant degradation capabilities, specifically polycyclic aromatic hydrocarbons. We also observed a strong association of plastic-degrading fungi (i.e., Cladosporium and Plectosphaerella) and early-diverging fungi (Cryptomycota, also known as Rozellomycota) with the plastisphere. Sea MPs were primarily colonised by fungi (70%), with a small proportion of river-transported microbes (1%-4%). The mere presence of MPs in seawater increased the relative abundance of planktonic fungi from 2% to 25%, suggesting significant exchanges between planktonic and plastisphere communities. Using microbial source tracking, we discovered that MPs only dispersed 3.5% and 5.5% of river bacterial and microeukaryotic communities into the sea, respectively. Hence, although MPs select and facilitate the dispersal of ecologically significant microorganisms, drastic compositional changes across distinct aquatic habitats are unlikely.

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.

Selective enrichment of bacteria and antibiotic resistance genes in microplastic biofilms and their potential hazards in coral reef ecosystems

Microplastics become hotspots for bacteria to trigger a series of ecological effects, but few studies have focused on the potential impacts of microplastic biofilms in coral reef ecosystems. Here, we measured the bacterial communities and antibiotic resistance genes (ARGs) in the seawater and microplastic biofilms. Results showed that microbial biofilms were formed on the surface of microplastics. The alpha diversity of the bacterial community in the microplastic biofilms was lower than that in the seawater, and the bacterial communities were distinct between the two. Further analysis revealed that several bacteria in the microplastic biofilms carried ARGs, and the proportion of which was correlated to the concentration of antibiotics in the seawater. Specifically, Vibrio was positively correlated to sul1 in the microplastic biofilms under higher concentrations of sulfonamides. Pathway analysis reflected significant overrepresentation of human disease related pathways in the bacterial community of microplastic biofilms. These results suggest that the microplastic biofilms could selectively enrich bacteria from the reef environments, causing the development of ARGs under antibiotic driving. This may pose a serious threat to coral reef ecosystems and human health. Our study provides new insights into the ecological impacts of microplastic biofilms in coral reef ecosystems.

Determinants of microbial colonization on microplastics through wastewater treatment processes: The role of polymer type and sequential treatment

This study examines the microbial colonization characteristics of microplastics (MPs) in wastewater treatment plants (WWTPs), focusing on polymer types (High-Density Polyethylene (HDPE) and Polyethylene Terephthalate (PET)) and various stages of wastewater treatments. Through individual and sequential deployment approaches, the research aimed to identify the determinants of bacterial colonization on MPs, whether they were introduced at each stage of treatment individually or in sequence from primary to tertiary stages. The study revealed that the stage of wastewater treatment profoundly influenced bacterial colonization on the polymer types MPs, with bacterial attachment being largely niche-specific. HDPE showed increased sensitivity to wastewater composition, leading to selective biofilm formation. For instance, in HDPE, Firmicutes accounted for 25.1 ± 0.04 % during primary treatment, while Alphaproteobacteria increased significantly in the tertiary treatment to 19.8 ± 0.1 %. Conversely, PET exhibited a stochastic pattern of bacterial colonization due to differences in surface hydrophilicity. Additionally, in sequential deployments, a notable shift towards stochastic bacterial attachment on MPs, particularly with HDPE was observed. The Shannon diversity values for MP biofilms were consistently higher than those for wastewater across all stages, with PET showing an increase in diversity in sequential deployments (Shannon diversity: 5.01 ± 0.03 for tertiary stage). These findings highlight the critical role of MPs as carriers of diverse bacteria, emphasizing the necessity for strategies to mitigate their impact in WWTPs. This study presents a significant advancement in our understanding of the interactions between MPs and microbial populations in WWTP environments.

Temporal dynamics of bacterial colonization on five types of microplastics in a freshwater lake

Microplastics (MPs), as a new substrate, provide a unique niche for microbial colonization in the freshwater ecosystems; however, the impacts of long-term MP exposure on colonized bacteria are still unclear. In this study, five MP types were exposed in a freshwater lake for approximately one year, and the MP particles, together with the surrounding water, were collected on days 60, 150, 250 and 330 during the in situ field experiment. Bacteria on the MP surface, as well as free-living bacteria in the surrounding water, were analyzed to evaluate the temporal dynamics of these bacterial communities. Results show that all five MP types exhibited signs of degradation during the exposure process. Additionally, the alpha diversity, community structure and composition of MP-attached bacteria significantly differed from that of the free-living bacteria in the surrounding water, indicating that the five MP types could provide a preferable niche for bacterial colonization in a freshwater environment. Proteobacteria, Chloroflexi, Verrucomicrobiota, Actinobacteriota and Firmicutes were the top five dominant phyla. Some plastic-degrading bacteria included in these phyla were detected, verifying that MP-attached biofilms had a certain degree of MP degradation potential. Some potentially pathogenic bacteria were also detected, suggesting an ecological threat for spreading disease in the aquatic ecosystem. Furthermore, the bacterial community and some metabolic pathways were significantly affected by the MP type (P < 0.01) and exposure time (P < 0.01), indicating that the presence of MPs not only alters the bacterial community structure and composition, but also influences their potential functional properties in freshwater ecosystems. Multiple factors, including the physicochemical properties related to MPs and the environmental parameters of the surrounding water, affect the community composition and the function of MP-attached bacteria to different degrees. Our findings indicate that the presence of MPs has a potential ecological impact on freshwater ecosystems.

Micro(nano)plastics in the Human Body: Sources, Occurrences, Fates, and Health Risks

The increasing global attention on micro(nano)plastics (MNPs) is a result of their ubiquity in the water, air, soil, and biosphere, exposing humans to MNPs on a daily basis and threatening human health. However, crucial data on MNPs in the human body, including the sources, occurrences, behaviors, and health risks, are limited, which greatly impedes any systematic assessment of their impact on the human body. To further understand the effects of MNPs on the human body, we must identify existing knowledge gaps that need to be immediately addressed and provide potential solutions to these issues. Herein, we examined the current literature on the sources, occurrences, and behaviors of MNPs in the human body as well as their potential health risks. Furthermore, we identified key knowledge gaps that must be resolved to comprehensively assess the effects of MNPs on human health. Additionally, we addressed that the complexity of MNPs and the lack of efficient analytical methods are the main barriers impeding current investigations on MNPs in the human body, necessitating the development of a standard and unified analytical method. Finally, we highlighted the need for interdisciplinary studies from environmental, biological, medical, chemical, computer, and material scientists to fill these knowledge gaps and drive further research. Considering the inevitability and daily occurrence of human exposure to MNPs, more studies are urgently required to enhance our understanding of their potential negative effects on human health.

Comprehensive understanding of the aging and biodegradation of polystyrene-based plastics

The extensive utilization and inadequate handling of plastics have resulted in severe environmental ramifications. In particular, plastics composed solely of a carbon-carbon (C-C) backbone exhibit limited degradation due to the absence of hydrolyzable functional groups. Plastics with enduring longevity in the natural environment are susceptible to environmental factors and their intrinsic properties, subsequently undergoing a series of aging processes that culminate in biodegradation. This article focuses on polystyrene (PS), which constitutes 20% of total plastic waste, as a case study. Initially, the application of PS in life and the impacts it poses are introduced. Following that, the key factors influencing the aging of PS are discussed, primarily encompassing its properties (e.g., surface characteristics, additives) and environmental factors (e.g., water matrices, biofilms). Lastly, an overview of microbial degradation of PS is provided, including potential microorganisms involved in PS degradation (bacteria, fungi, algae, and insects), four processes of microbial degradation (colonization, bio-fragmentation, assimilation, and mineralization), and potential mechanisms of microbial degradation. This study provides a comprehensive understanding of the multifaceted influences affecting the aging and biodegradation mechanisms of PS, thereby contributing valuable insights for the future management of plastic pollution.

Microbial colonization and chemically influenced selective enrichment of bacterial pathogens on polycarbonate plastic

Plastic pollution in aquatic environments poses significant concerns due to its potential to serve as a refuge for aquatic pathogens. However, the role of plastic surfaces and microbial biofilm interfaces in facilitating pathogen development remains poorly understood. In this study, a microcosm setup was employed to investigate the interactions between plastics and the microbial community and examine the differences in bacterial community composition and potential pathogen occurrences between the plastisphere-biofilm and surrounding seawater. Community composition analysis combined with SEM observations over time indicated that biofilm extracellular polymeric substance formation over 14 days had a link with the relative abundance and succession patterns of pathogen taxa. Colony clusters were observed on biofilms from day 7 and coincided with higher bacterial pathogen dominance. On day 14, pathogen abundance overall decreased with a potentially degrading biofilm. Pseudomonas and Pseudoalteromonas were the dominant potential pathogen groups observed in the microcosm. When further subjected to chemical treatment as an imposed environmental stress over time, biofilm-associated Psuedoalteromonas sharply increased in abundance after three days of exposure, but quickly diminished by 14 days in favor of genera such as Acinetobacter, Pseudomonas, and Staphylococcus. These results suggest that environmental plastisphere-biofilms can promote the early selection, enrichment, and spread of pathogenic bacteria in the aquatic environment and could be later worsened under chemical and long-term pressure. This study provided new insights into the succession of pathogens in plastisphere biofilms, contributing to the understanding of pathogen risks involved in emerging plastisphere biofilms in light of global plastic pollution.

Microbial colonization patterns and biodegradation of petrochemical and biodegradable plastics in lake waters: insights from a field experiment

Introduction

Once dispersed in water, plastic materials become promptly colonized by biofilm-forming microorganisms, commonly known as plastisphere.

Methods

By combining DNA sequencing and Confocal Laser Scanning Microscopy (CLSM), we investigated the plastisphere colonization patterns following exposure to natural lake waters (up to 77 days) of either petrochemical or biodegradable plastic materials (low density polyethylene - LDPE, polyethylene terephthalate - PET, polylactic acid - PLA, and the starch-based MaterBi® - Mb) in comparison to planktonic community composition. Chemical composition, water wettability, and morphology of plastic surfaces were evaluated, through Transform Infrared Spectroscopy (ATR-FTIR), Scanning Electron Microscopy (SEM), and static contact angle analysis, to assess the possible effects of microbial colonization and biodegradation activity.

Results and Discussion

The phylogenetic composition of plastisphere and planktonic communities was notably different. Pioneering microbial colonisers, likely selected from lake waters, were found associated with all plastic materials, along with a core of more than 30 abundant bacterial families associated with all polymers. The different plastic materials, either derived from petrochemical hydrocarbons (i.e., LDPE and PET) or biodegradable (PLA and Mb), were used by opportunistic aquatic microorganisms as adhesion surfaces rather than carbon sources. The Mb-associated microorganisms (i.e. mostly members of the family Burkholderiaceae) were likely able to degrade the starch residues on the polymer surfaces, although the Mb matrix maintained its original chemical structure and morphology. Overall, our findings provide insights into the complex interactions between aquatic microorganisms and plastic materials found in lake waters, highlighting the importance of understanding the plastisphere dynamics to better manage the fate of plastic debris in the environment.

Assessment of Biofilm Growth on Microplastics in Freshwaters Using a Passive Flow-Through System

Biofilms that colonize on the surface of microplastics (MPs) in freshwaters may pose a potential health risk. This study examined factors that influence MP-associated biofilm growth, including polymer type, degree of weathering, and source water quality. Weathered MPs produced in-lab were employed in biofilm trials conducted on site using a passive flow-through system with raw water at drinking water treatment facility intakes. Adenosine triphosphate (ATP) was used to quantify biofilm abundance; biofilm composition was assessed via metagenomic sequencing. Biofilm growth was observed on all polymer types examined and most prevalent on polyvinyl chloride (PVC), where ATP levels were 6 to 12 times higher when compared to other polymers. Pathogen-containing species including Salmonella enterica and Escherichia coli were present on all polymers with relative abundance up to 13.7%. S. enterica was selectively enriched on weathered MPs in specific water matrices. These findings support the need to research the potential accumulation of pathogenic organisms on microplastic surfaces.

Microbial interactions within beneficial consortia promote soil health

By ecologically interacting with various biotic and abiotic agents acting in soil ecosystems, highly diverse soil microorganisms establish complex and stable assemblages and survive in a community context in natural settings. Besides facilitating soil microbiome to maintain great levels of population homeostasis, such microbial interactions drive soil microbes to function as the major engine of terrestrial biogeochemical cycling. It is verified that the regulative effect of microbe-microbe interplay plays an instrumental role in microbial-mediated promotion of soil health, including bioremediation of soil pollutants and biocontrol of soil-borne phytopathogens, which is considered an environmentally friendly strategy for ensuring the healthy condition of soils. Specifically, in microbial consortia, it has been proven that microorganism-microorganism interactions are involved in enhancing the soil health-promoting effectiveness (i.e., efficacies of pollution reduction and disease inhibition) of the beneficial microbes, here defined as soil health-promoting agents. These microbial interactions can positively regulate the soil health-enhancing effect by supporting those soil health-promoting agents utilized in combination, as multi-strain soil health-promoting agents, to overcome three main obstacles: inadequate soil colonization, insufficient soil contaminant eradication and inefficient soil-borne pathogen suppression, all of which can restrict their probiotic functionality. Yet the mechanisms underlying such beneficial interaction-related adjustments and how to efficiently assemble soil health-enhancing consortia with the guidance of microbe-microbe communications remain incompletely understood. In this review, we focus on bacterial and fungal soil health-promoting agents to summarize current research progress on the utilization of multi-strain soil health-promoting agents in the control of soil pollution and soil-borne plant diseases. We discuss potential microbial interaction-relevant mechanisms deployed by the probiotic microorganisms to upgrade their functions in managing soil health. We emphasize the interplay-related factors that should be taken into account when building soil health-promoting consortia, and propose a workflow for assembling them by employing a reductionist synthetic community approach.

The hind information: Exploring the impact of physical damage on mask microbial composition in the aquatic environment

Due to poor management and the lack of environmental awareness, lots of masks (an emerging form of plastic pollution) are discarded into the environment during the COVID-19, thereby jeopardizing the health of humans and the environment. Our study introduces a novel perspective by examining the impact of physical damage on the microbial composition of masks in the water environment. We focus on the variations in biofilm formation on each layer of both damaged and undamaged masks, which allows us to understand more about the biofilm on each layer and the significant changes that occur when masks are physically damaged. Research has shown that the community structure of microorganisms on discarded masks can be altered in just ten days, showing an evolution from undifferentiated pioneer colonizing species ("non-picky") to adaptive dominant species ("picky"). Especially, considering that discarded masks were inevitably damaged, we found that the biomass on the damaged samples is 1.62-2.38 times higher than that of the undamaged samples, respectively. Moreover, the microbial community structure on it was also significantly different. Genes involved in biogeochemical cycles of nutrients are more enriched in damaged masks. When damaged, the colonization process and community structure in the middle layer significantly differ from those in the inner and outer layers and even enrich more pathogenic bacteria. Based on the above, it is evident that the environmental risk of masks cannot be assessed as a whole, and the middle layer carries a higher risk.

Effects of microplastics on denitrification and associated N2O emission in estuarine and coastal sediments: insights from interactions between sulfate reducers and denitrifiers

Global estuarine and coastal zones are facing severe microplastics (MPs) pollution. Sulfate reducers (SRB) and denitrifiers (DNB) are two key functional microorganisms in these zones, exhibiting intricate interactions. However, whether and how MPs modulate the interactions between SRB and DNB, with implications for denitrification and associated N2O emissions, remains poorly understood. Here, we simultaneously investigated the spatial response patterns of SRB-DNB interactions and denitrification and associated N2O emissions to different MPs exposure along an estuarine gradient in the Yangtze Estuary. Spatial responses of denitrification to polyvinyl chloride (PVC) and polyadipate/butylene terephthalate (PBAT) MPs exposure were heterogeneous, while those of N2O emissions were not. Gradient-boosted regression tree and multiple regression model analyses showed that sulfide, followed by nitrate (NO3-), controlled the response patterns of denitrification to MPs exposure. Further mechanistic investigation revealed that exposure to MPs resulted in a competitive and toxic (sulfide accumulation) inhibition of SRB on DNB, ultimately inhibiting denitrification at upstream zones with high sulfide but low NO3- levels. Conversely, MPs exposure induced a competitive inhibition of DNB on SRB, generally promoting denitrification at downstream zones with low sulfide but high NO3- levels. These findings advance the current understanding of the impacts of MPs on nitrogen cycle in estuarine and coastal zones, and provide a novel insight for future studies exploring the response of biogeochemical cycles to MPs in various ecosystems.

Long-term effect of seasonal and constant low temperatures on mesophilic biomass treating sewage in continuously stirred tank anaerobic granular reactor

A Continuously Stirred Tank Anaerobic Granular Reactor seeded with mesophilic biomass was studied for 1733 days analysing the impact of seasonal (12-23 °C) and controlled (8-15 °C) low temperatures on anaerobic treatment of sewage. Aided by intermittent dosing of 0.04% (v/v) methanol, the microbiota quickly adapted to temperature fluctuations. Chemical oxygen demand (COD) removal efficiency was high but low temperatures affected methane production. Under low-temperature stress, the Methanomythylovorans and Methanosaeta-dominated methanogenic community shifted focus to cellular repair and transport, with carbon diversion towards assimilative pathways, thereby decreasing methane yields. Specific methanogenic activity at 15 °C and 30 °C increased by five and four times, respectively, from their initial values indicating microbiota retained its mesophilic properties. Despite lower methane yield, stable and high COD removals, along with low dissolved methane and volatile fatty acids indicated that low-temperature anaerobic sewage treatment using mesophilic biomass in the long run is sustainable.

Plastic mulching, and occurrence, incorporation, degradation, and impacts of polyethylene microplastics in agroecosystems

Polyethylene microplastics have been detected in farmland soil, irrigation water, and soil organisms in agroecosystems, while plastic mulching is suggested as a crucial source of microplastic pollution in the agroecosystem. Plastic mulch can be broken down from plastic mulch debris to microplastics through environmental aging and degradation process in farmlands, and the colonization of polyethylene-degrading microorganisms on polyethylene microplastics can eventually enzymatically depolymerize the polyethylene molecular chains with CO2 release through the tricarboxylic acid cycle. The selective colonization of microplastics by soil microorganisms can cause changes in soil microbial community composition, and it can consequently elicit changes in enzyme activities and nutrient element content in the soil. The biological uptake of polyethylene microplastics and the associated disturbance of energy investment are the main mechanisms impacting soil-dwelling animal development and behavior. As polyethylene microplastics are highly hydrophobic, their presence among soil particles can contribute to soil water repellency and influence soil water availability. Polyethylene microplastics have been shown to cause impacts on crop plant growth, as manifested by the effects of polyethylene microplastics on soil properties and soil biota in the agroecosystems. This review reveals the degradation process, biological impacts, and associated mechanisms of polyethylene microplastics in agroecosystems and could be a critical reference for their risk assessment and management.

A preliminary study about the potential risks of the UV-weathered microplastic: The proteome-level changes in the brain in response to polystyrene derived weathered microplastics

The growing use of plastic materials has resulted in a constant increase in the risk associated with microplastics (MPs). Ultra-violet (UV) light and wind break down modify MPs in the environment into smaller particles known as weathered MPs (WMPs) and these processes increase the risk of MP toxicity. The neurotoxicity of weathered polystyrene-MPs remains unclear. Therefore, it is important to understand the risks posed by WMPs. We evaluated the chemical changes of WMPs generated under laboratory-synchronized environmentally mimetic conditions and compared them with virgin MPs (VMPs). We found that WMP had a rough surface, slight yellow color, reduced molecular weight, and structural alteration compared with those of VMP. Next, 2 μg of ∼100 μm in size of WMP and VMP were orally administered once a day for one week to C57BL/6 male mice. Proteomic analysis revealed that the WMP group had significantly increased activation of immune and neurodegeneration-related pathways compared with that of the VMP group. Consistently, in in vitro experiments, the human brain-derived microglial cell line (HMC-3) also exhibited a more severe inflammatory response to WMP than to VMP. These results show that WMP is a more profound inflammatory factor than VMP. In summary, our findings demonstrate the toxicity of WMPs and provide theoretical insights into their potential risks to biological systems and even humans in the ecosystem.

Enhanced bacterial adhesion force by rifampicin resistance promotes microbial colonization on PE plastic compared to non-resistant biofilm formation

The microbial biofilm formed on plastics, is ubiquitous in the environment. However, the effects of antibiotic resistance on the development of the biofilm on plastics, especially with regard to initial cell attachment, remain unclear. In this study, we investigated the initial bacterial adhesion and subsequent biofilm growth of a rifampin (Rif) resistant E. coli (RRE) and a normal gram-positive B. subtilis on a typical plastic (polyethylene, PE). The experiments were conducted in different antibiotic solutions, including Rif, sulfamethoxazole (SMX), and kanamycin (KM), with concentrations ranging from 1 to 1000 μg/L to simulate different aquatic environments. The AFM-based single-cell adhesion force determination revealed that Rif resistance strengthened the adhesion force of RRE to PE in the environment rich in Rif rather than SMX and KM. The enhanced adhesion force may be due to the higher secretion of extracellular polymeric substances (EPS), particularly proteins, by RRE in the presence of Rif compared to the other two antibiotics. In addition, the higher ATP level of RRE would facilitate the initial adhesion and subsequent biofilm growth. Transcriptome analysis of RRE separately cultured in Rif and SMX environments demonstrated a clear correlation between the expression of Rif resistance and the augmented bacterial adhesion and cellular activity. Biofilm biomass analysis confirmed the promotion effect of Rif resistance on biofilm growth when compared to non-resistant biofilms, establishing a novel association with the augmentation of microbial adhesion force. Our study highlights concerns related to the dissemination of antibiotic resistance during microbial colonization on plastic that may arise from antibiotic resistance.

Microplastics Reshape the Fate of Aqueous Carbon by Inducing Dynamic Changes in Biodiversity and Chemodiversity

The interactions among dissolved organic matter (DOM), microplastics (MPs) and microbes influence the fate of aqueous carbon and greenhouse gas emissions. However, the related processes and mechanisms remain unclear. Here, we found that MPs determined the fate of aqueous carbon by influencing biodiversity and chemodiversity. MPs release chemical additives such as diethylhexyl phthalate (DEHP) and bisphenol A (BPA) into the aqueous phase. The microbial community, especially autotrophic bacteria such as Cyanobacteria, showed a negative correlation with the additives released from MPs. The inhibition of autotrophs promoted CO₂ emissions. Meanwhile, MPs stimulated microbial metabolic pathways such as the tricarboxylic acid (TCA) cycle to accelerate the DOM biodegradation process, and then the transformed DOM presented low bioavailability, high stability, and aromaticity. Our findings highlight an urgent need for chemodiversity and biodiversity surveys to assess ecological risks from MP pollution and the impact of MPs on the carbon cycle.

Microbial community assembly responses to polycyclic aromatic hydrocarbon contamination across water and sediment habitats in the Pearl River Estuary

Along with rapid urbanization and intensive human activities, polycyclic aromatic hydrocarbon (PAH) pollution in the Pearl River Estuary (PRE) and its effects on the microbial community have attracted extensive attention. However, the potential and mechanism of microbial degradation of PAHs across water and sediment habitats remain obscure. Herein, the estuarine microbial community structure, function, assembly process and co-occurrence patterns impacted by PAHs were comprehensively analyzed using environmental DNA-based approaches. The contamination and distribution of PAHs were jointly affected by anthropogenic and natural factors. Some of the keystone taxa were identified as PAH-degrading bacteria (i.e., genera Defluviimonas, Mycobacterium, families 67-14, Rhodobacteraceae, Microbacteriaceae and order Gaiellales in water) or biomarkers (i.e., Gaiellales in sediment) that were significantly correlated with PAH levels. The proportion of deterministic process in the high PAH-polluted water (76%) was much higher than that in the low pollution area (7%), confirming the significant effect of PAHs on the microbial community assembly. In sediment, the communities with high phylogenetic diversity demonstrated a great extent of niche differentiation, exhibited a stronger response to environmental variables and were strongly influenced by deterministic processes (40%). Overall, deterministic and stochastic processes are closely related to the distribution and mass transfer of pollutants, and substantially affect the biological aggregation and interspecies interaction within communities in the habitats.

Biomass formation and organic carbon migration potential of microplastics from a PET recycling plant: Implication of biostability

The growth of the polyethylene terephthalate (PET) mechanical recycling industry has resulted in the challenge of generating microplastics (MPs). However, little attention has been given to investigating the release of organic carbon from these MPs and their roles in promoting bacterial growth in aquatic environments. In this study, a comprehensive method is proposed to access the potential of organic carbon migration and biomass formation of MPs generated from a PET recycling plant, and to understand its impact on the biological systems of freshwater habitats. Various MPs sizes from a PET recycling plant were selected to conduct a series of tests, including the organic carbon migration test, biomass formation potential test, and microbial community analysis. The MPs smaller than 100 µm, which are difficult to remove from the wastewater, exhibited greater biomass in the observed samples (1.05 × 10¹¹ bacteria per gram MPs). Moreover, PET MPs altered the microbial diversity, with Burkholderiaceae becoming the most abundant, while Rhodobacteraceae was eliminated after being incubated with MPs. This study partly revealed that organic matter adsorbed on the surface of MPs was a significant nutrient source that increased biomass formation. PET MPs acted not only as carriers for microorganisms but also for organic matter. As a result, it is crucial to develop and refine recycling methods in order to decrease the production of PET MPs and minimize their adverse effects on the environment.

Deciphering the distinct successional patterns and potential roles of abundant and rare microbial taxa of urban riverine plastisphere

Microbial colonization on microplastics has provoked global concern; however, many studies have not considered the successional patterns and potential roles of abundant and rare taxa of the plastisphere during colonization. Hence, we investigate the taxonomic composition, assembly, interaction and function of abundant and rare taxa in the riverine plastisphere by conducting microcosm experiments. Results showed that rare taxa occupied significantly high community diversity and niche breadth than the abundant taxa, which implies that rare taxa are essential components in maintaining the community stability of the plastisphere. However, the abundant taxa played a major role in driving the succession of plastisphere communities during colonization. Both stochastic and deterministic processes signally affected the plastisphere community assemblies; while, the deterministic patterns (heterogeneous selection) were especially pronounced for rare biospheres. Plastisphere microbial networks were shaped by the enhancement of network modularity and reinforcement of positive interactions. Rare taxa played critical roles in shaping stable plastisphere by occupying the key status in microbial networks. The strong interaction of rare and non-rare taxa suggested that multi-species collaboration might be conducive to the formation and stability of the plastisphere. Both abundant and rare taxa were enriched with plentiful functional genes related to carbon, nitrogen, phosphorus and sulfur cycling; however, their potential metabolic functions were significantly discrepant, implying that the abundant and rare microbes may play different roles in ecosystems. Overall, this study strengthens our comprehending of the mechanisms regarding the formation and maintenance of the plastisphere.

Plastisphere microbiome: Methodology, diversity, and functionality

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

Effects of plastisphere on phosphorus availability in freshwater system: Critical roles of polymer type and colonizing habitat

Biofilm covered microplastics (BMPs) can act as vectors for the transport of exogenous microbial groups to aquatic ecosystem. However, a consensus regarding the formation and development of BMPs and their effect on phosphorus (P) availability has not been reached. Herein, plastic particles made of fuel-based (PET) and biobased polymers (PLA) were deployed in water and hyporheic zones of an urban river for biofilm colonization. Then, BMPs were transferred to lab incubation to study their effects on the P availability. The results showed that different microplastic biofilms had various bacteria and phytoplankton compositions. Additionally, BMPs induced a shift in the microbial co-occurrence patterns co-differentiated by polymer type and colonizing habitats. Network analyses revealed that the structure of PLA BMPs was more robust, while PET colonized in the hyporheic zone reduced network complexity with looser connections between species, and stronger negatively correlated interactions. However, PET formed denser biofilms by the excretion of extracellular polymeric substances from microalgae, which contributed to the better capacity of P utilization. PET colonized in the water/hyporheic zone significantly decreased soluble reactive phosphate by 42.5 % and 30.8 %, respectively. The abovementioned results indicated that BMPs have the potential to disrupt nutrient availability. This study broadens our perspectives for the ecological effects of BMPs in the aquatic environment.