Bacterial community are more susceptible to nanoplastics than algae community in aquatic ecosystems dominated by submerged macrophytes

Silver nanoparticles alter plankton-mediated carbon cycle processes in freshwater mesocosms

Understanding the ecological impacts of nanoparticle exposure has become increasingly urgent, as these materials are now widespread in aquatic environments. However, the effects of nanoparticle exposure on plankton community-mediated carbon cycling remain poorly understood. This study investigated the effects of long-term (28-day) exposure to environmentally relevant concentrations (10 and 100 µg/L) of silver nanoparticles (AgNPs) on the plankton-mediated carbon cycling processes of freshwater ecosystems by constructing a mesocosm ecosystem. The results showed that AgNP exposure enhanced the photosynthetic activity and biomass of both phytoplankton and zooplankton, thereby promoting carbon fixation. AgNP exposure also increased the ecological niche breadth and carbon source utilization of planktonic microorganisms while disrupting lipid metabolism, which facilitated carbon decomposition and utilization. Furthermore, AgNPs promoted the transformation of organic carbon by reducing the content and chemical composition of dissolved organic carbon and increasing the sedimentation of particulate organic carbon in the plankton community. Notably, compared with the control, exposure to 10 and 100 µg/L AgNPs reduced CO2 release at the water-air interface by 9 % and 17 %, respectively. Overall, this study provides the first evidence that long-term exposure to AgNPs can alter plankton-mediated carbon cycling processes in aquatic ecosystems, offering new insights into the ecotoxicological effects and risk assessment of nanoparticles.

Polystyrene nanoplastics reshape the peatland plants (Sphagnum) bacteriome under simulated wet-deposition pathway: Insights into unequal impact of ecological niches

Nanoplastics (NPs) enter peatlands through atmospheric deposition, yet their effects on Sphagnum bacterial communities (SBCs) and plant-self remain unknown. We hypothesize that NPs alter the composition, structure, and co-occurrence pattern of epiphytes (Epi) and endophytes (En), thereby differentially affecting the growth and physiological performance of Sphagnum. The 30-day simulated wet deposition experiment was conducted to test this. Here, polystyrene NPs reduced the α-diversity of SBCs, unevenly reshaped the structure of Epi and En. Mfuzz clustering was used to reveal the co-abundance behavior of SBCs, and the null model found SBCs relied on stochastic assembly, formed stable Epi molecular ecological network (MEN) and connected En MEN. NPs disrupted symbiosis of SBCs, with high-abundance phyla reductions impacting MENs and low-abundance phyla affecting the inter-domain ecological network (IDEN) between Epi and En. Increasingly positive NPs (from carboxyl-modified to unmodified, and then to amino-modified NPs) further decreased SBCs abundance. Key clusters of Proteobacteria (Pro.), with α-Pro. and γ-Pro. as module hubs of MENs, and β-Pro. as a network hub in the IDEN, could reflect these changes. Additionally, NPs lowered plant spread area (P < 0.05) and chlorophyll content (P < 0.01), but the reduction in biomass was not significant. Structural equation modeling showed reduced SBCs α-diversity alleviated the NPs phytotoxicity (up to 33.31 % offset), as genetic analysis revealed that methane oxidation, carbon fixation, and trace element metabolism may upregulate plant nutrient supply. Our findings offer critical insights into NPs deposition risks in remote areas and highlight the responses of plant-bacteriome symbiosis.

Quantification of the Uptake and Biodistribution of Nanoplastics in Escherichia coli

Nanoplastics (NPs) are prevalent in the environment, posing risks to ecosystems and human health. While research into their effects on bacterial activity has increased, the mechanisms underlying NP-bacteria interactions─specifically whether NPs penetrate cells or adhere to the cell surface─remain poorly understood. This knowledge gap largely stems from the absence of quantitative analytical methods. Herein, we developed a novel approach combining lysozyme treatment with pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) to differentiate between intracellular and cell wall-bound NPs in Escherichia coli (E. coli) quantitatively. The method involves selective removal of the bacterial cell wall using lysozyme, protein corona-induced extraction to enrich cell wall-bound NPs, and hydrogen peroxide digestion to eliminate protoplast interference before Py-GC/MS analysis. Validation with europium (Eu)-labeled NPs, quantified by inductively coupled plasma mass spectrometry (ICP-MS), confirmed the method's accuracy and reliability. Using this approach, we found that after NP exposure, only a small fraction (9.6-10.5%) of NPs penetrated E. coli cells, while the majority (36.9-63.8%) adhered to the cell surface. Transmission electron microscopy further corroborated these findings. Consequently, this work provides a robust tool for the quantification of NP uptake and biodistribution in bacterial systems, advancing our understanding of NP-microorganism interactions and their environmental implications.

Polycaprolactam microplastics reduce allelopathic potential of Iris pseudacorus via toxic effects on stimulatory bacteria

Many studies have investigated the toxic effects of microplastics (MPs) ingested by aquatic animals, but the effects of MPs that adhere to the roots of macrophytes require further exploration. Thus, the present study investigated the dose-dependent toxic effects of adding 10-500 mg/kg of polycaprolactam microplastics (PCM) on allelopathic cyanobacterial inhibition by a wetland macrophyte due to the influence on rhizosphere bacteria in a pot trial. First, comparisons of sterilized and unsterilized Iris pseudacorus rhizosphere soil showed that the unsterilized soil could enhance the root activity and allelopathic inhibition of Microcystis aeruginosa cyanobacteria. Furthermore, adding 50-100 mg/kg PCM to the unsterilized soil significantly altered the abundances of many types of bacteria, and decreased the root activity and bacterial biodiversity in the rhizosphere. Importantly, PCM changed the secondary metabolites profile in the roots, as well as decreasing production of the allelochemical palmitic acid and the allelopathic potential of I. pseudacorus. Moreover, a dominant strain of functional bacterium AAP51 was identified as an allelopathic promoter, isolated, and successfully inoculated into the sterilized soil. The decomposition of PCM produced the toxic monomer caprolactam in the rhizosphere soil at an average rate of 0.067 mg/kg·d under treatment with 50 mg/kg PCM. Toxicological testing showed that 5 mg/kg caprolactam inhibited the activities of the dominant bacteria and expression of the allelopathic gene FAD2 to weaken the allelopathic effect of I. pseudacorus. Thus, the findings obtained in this study indicate that PCM inhibited the allelopathic potential of the macrophyte due to the release of toxic caprolactam damaging bacteria in the rhizosphere. Consequently, it is necessary to remove MP pollutants from aquatic ecosystems in order to maintain the strong allelopathic potential of macrophytes and efficiently control cyanobacterial blooms.

Spatial heterogeneity of EPS-mediated microplastic aggregation in phycosphere shapes polymer-specific Trojan horse effects

The pervasive contamination of aquatic ecosystems by microplastics represented a critical environmental challenge. While algal-bacterial symbiosis systems demonstrated potential for microplastic aggregation via extracellular polymeric substances (EPS), prior studies have focused on temporal dynamics rather than spatial heterogeneity in phycosphere. This study systematically investigated the adsorption mechanisms of Polyvinyl chloride (PVC), polyethylene terephthalate (PET), polyethylene (PE) and polystyrene (PS) across stratified EPS fractions, tightly bound (TB-EPS), loosely bound (LB-EPS), and soluble (S-EPS), in phycosphere. Combining controlled aggregation assays with multimodal characterization, we revealed a hierarchical spatial framework governing EPS-microplastic interactions. Adsorption efficiency governed by polymer-specific interfacial energies and EPS organic composition. EPS at distinct hierarchical levels exhibited material-specific adsorption preferences for microplastics. PVC and PET demonstrated higher affinities for hydrocarbon components, while PE and PS were preferentially captured through interactions with polysaccharides and amide I groups, respectively. The adsorption and aggregation behaviors between EPS and microplastics in the phycosphere promoted eco-corona formation and induced the Trojan horse effect. However, the energy barrier of interaction forces and EPS spatial configurations jointly governed the hierarchical stabilization of polymer-specific microplastics. PVC and PET primarily colonized the outermost S-EPS layer, PS preferentially accumulated in the intermediate LB-EPS layer, and PE penetrated into the innermost TB-EPS layer. These findings addressed a key knowledge gap by delineating the ecological niche-specific distribution of EPS-microplastic binding, offering novel insights for optimizing bioremediation strategies and informing regulatory measures targeting particulate plastic pollution in hydrologic systems.

Microalgae - bacteria based wastewater treatment systems: Granulation, influence factors and pollutants removal

Wastewater treatment based on microalgae and bacteria symbiosis is an environmentally friendly, sustainable technology that has attracted attention recently because of its high efficiency in treating pollutants, saving energy, and short-term biomass recovery. Among them, the granular microalgae and bacteria combination emerges with the advantages of rapid gravity settling, good resistance to adverse environmental conditions, outstanding wastewater treatment performance, and easy biomass recovery. This review aims to clarify the microalgal-bacterial granule (MBG) - based process for wastewater treatment. In particular, MBG characteristics, granulation mechanism, and influence factors on the process are also discussed. The review contributes to the knowledge system related to MBG research in recent years, thereby pointing out research gaps that need to be filled in the future.

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.

Assessing the efficacy of natural soil biotin on soil quality, microbial diversity, and Rhododendron simsii growth for sustainable landscape architecture

Fertilization significantly influences soil quality and its sustainable use in urban garden maintenance. The widespread application of inorganic fertilizers has raised ecological concerns due to their potential environmental impacts. Organic fertilizers, while beneficial, often have slow effects and are costly. Biofertilizers, with their eco-friendly nature and low carbon footprint, are gaining attention for their multifaceted role in supporting plant growth. Despite the focus on fruit trees, vegetables, and medicinal plants, ornamental plants have been understudied. This study aims to evaluate the efficacy of a novel microbial fertilizer, 'natural soil biotin', on Rhododendron plants, specifically the Azalea hybrid 'Carnation'. The study employed a comparative approach to assess the impact of different fertilization strategies on soil properties, microbial diversity, enzyme activity, plant morphology, and physiological parameters. The application of 'natural soil biotin' was compared with the use of inorganic and organic fertilizers. The combined application of 'natural soil biotin' was found to effectively enhance soil properties and mitigate the impact of other fertilizers on soil pH. It also improved the relative abundance of beneficial microbial groups such as Proteobacteria, Ascomycota, and Basidiomycota. Furthermore, the mixed application significantly increased the activities of urease and sucrase in Rhododendron plants, which promoted their growth, development, and stress resistance. The results indicate that the mixed application of 'natural soil biotin' with inorganic and organic fertilizers not only improved the soil quality but also enhanced the efficiency of fertilizer utilization. This approach led to increased economic and environmental benefits in Rhododendron cultivation. The findings contribute to the foundation for soil improvement and ecological restoration, suggesting that 'natural soil biotin' could be a promising alternative or supplement to traditional fertilization methods in sustainable landscape architecture.

Fate and removal of fluoroquinolone antibiotics in mesocosmic wetlands: Impact on wetland performance, resistance genes and microbial communities

The fate of fluoroquinolone antibiotics norfloxacin and ofloxacin were investigated in mesocosmic wetlands, along with their effects on nutrients removal, antibiotic resistance genes (ARGs) and epiphytic microbial communities on Hydrilla verticillate using bionic plants as control groups. Approximately 99% of norfloxacin and ofloxacin were removed from overlaying water, and H. verticillate inhibited fluoroquinolones accumulation in surface sediments compared to bionic plants. Partial least squares path modeling showed that antibiotics significantly inhibited the nutrient removal capacity (0.55) but had no direct effect on plant physiology. Ofloxacin impaired wetland performance more strongly than norfloxacin and more impacted the primary microbial phyla, whereas substrates played the most decisive role on microbial diversities. High antibiotics concentration shifted the most dominant phyla from Proteobacteria to Bacteroidetes and inhibited the Xenobiotics biodegradation function, contributing to the aggravation in wetland performance. Dechloromonas and Pseudomonas were regarded as the key microorganisms for antibiotics degradation. Co-occurrence network analysis excavated that microorganisms degrade antibiotics mainly through co-metabolism, and more complexity and facilitation/reciprocity between microbes attached to submerged plants compared to bionic plants. Furthermore, environmental factors influenced ARGs mainly by altering the community dynamics of differential bacteria. This study offers new insights into antibiotic removal and regulation of ARGs accumulation in wetlands with submerged macrophyte.

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.

The toxicity of polystyrene micro- and nano-plastics on rare minnow (Gobiocypris rarus) varies with the particle size and concentration

How the particle size and concentration of microplastics impact their toxicity is largely unknown. Herein, the effects of polystyrene microplastics (1 μm, MPs) and nanoplastics (100 nm, NPs) exposed at 1 mg/L (L) and 10 mg/L (H), respectively, on the growth, histopathology, oxidative stress, gut microbiome, and metabolism of rare minnow (Gobiocypris rarus) were investigated by chemical analysis and multi-omics. MPs and NPs inhibited the growth, induced histopathological injury and aggravated oxidative stress markedly with contrasting significance of particle size and concentration. The composition of core gut microbiota changed dramatically especially for the MPs-H. Similarly, gut bacterial communities were reshaped by the MPs and NPs but only NPs-H decreased both richness and Shannon indexes significantly. Co-occurrence network analysis revealed that the potential keystone genera underwent great changes in exposed groups compared to the control. MPs-H increased the network complexity and the frequency of positive interactions which was opposite to other exposed groups. Moreover, the metabolomic profiles associated with amino acid, lipid, unsaturated fatty acid and hormone metabolism were disturbed significantly especially for MPs-H and NPs-H. In conclusion, the toxicity of MPs depends on both the particle size and concentration, and varies with the specific indicators as well.

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.

Response strategies of stem/leaves endophyte communities to nano-plastics regulate growth performance of submerged macrophytes

Research on the toxicity effects of nano-plastics on submerged macrophytes has been increasing over the past several years. However, how the endophytic bacteria of submerged macrophytes respond to nano-plastics remains unknown, although they have been widely shown to help terrestrial plants cope with various environmental stressors. Here, a microcosm experiment was performed to unravel the effects of high concentration of nano-plastics (20 mg/L) on three submerged macrophyte (Vallisneria natans, Potamogeton maackianus, Myriophyllum spicatum) and their endophytic bacterial communities. Results indicated that nano-plastics induced antioxidative stress in plants, but significantly reduction in relative growth rate (RGR) only occurred in V. natans (from 0.0034 to -0.0029 day-1), accompanied by change in the stem/leaves endophyte community composition. Further analysis suggested nano-plastics caused a reduction in environmental nutrient availability and the proportion of positive interactions between endophyte communities (43%), resulting in the lowest RGR of V. natans. In contrast, endophytes may help P. maackianus and M. spicatum cope with nano-plastic stress by increasing the proportion of positive correlations among communities (70% and 75%), leaving their RGR unaffected. Collectively, our study elucidates the species-specific response strategies of submerged macrophyte-endophyte to nano-plastics, which helps to reveal the different phytoremediation potential of submerged macrophytes against nano-plastic pollution.

Toxicity Mechanisms of Nanoplastics on Crop Growth, Interference of Phyllosphere Microbes, and Evidence for Foliar Penetration and Translocation

Despite the increasing prevalence of atmospheric nanoplastics (NPs), there remains limited research on their phytotoxicity, foliar absorption, and translocation in plants. In this study, we aimed to fill this knowledge gap by investigating the physiological effects of tomato leaves exposed to differently charged NPs and foliar absorption and translocation of NPs. We found that positively charged NPs caused more pronounced physiological effects, including growth inhibition, increased antioxidant enzyme activity, and altered gene expression and metabolite composition and even significantly changed the structure and composition of the phyllosphere microbial community. Also, differently charged NPs exhibited differential foliar absorption and translocation, with the positively charged NPs penetrating more into the leaves and dispersing uniformly within the mesophyll cells. Additionally, NPs absorbed by the leaves were able to translocate to the roots. These findings provide important insights into the interactions between atmospheric NPs and crop plants and demonstrate that NPs' accumulation in crops could negatively impact agricultural production and food safety.

Advances in responses of microalgal-bacterial symbiosis to emerging pollutants in wastewater

Nowadays, emerging pollutants are widely used and exist in wastewater, such as antibiotics, heavy metals, nanoparticle and microplastic. As a green alternative for wastewater treatment, microalgal-bacterial symbiosis has been aware of owning multiple merits of low energy consumption and little greenhouse gas emission. Thus, the responses of microalgal-bacterial symbiosis to emerging pollutants in wastewater treatment have become a hotspot in recent years. In this review paper, the removal performance of microalgal-bacterial symbiosis on organics, nitrogen and phosphorus in wastewater containing emerging pollutants has been summarized. The adaptation mechanisms of microalgal-bacterial symbiosis to emerging pollutants have been analyzed. It is found that antibiotics usually have hormesis effects on microalgal-bacterial symbiosis, and that microalgal-bacterial symbiosis appears to show more capacity to remove tetracycline and sulfamethoxazole, rather than oxytetracycline and enrofloxacin. Generally, microalgal-bacterial symbiosis can adapt to heavy metals at a concentration of less than 1 mg/L, but its capabilities to remove contaminants can be significantly affected at 10 mg/L heavy metals. Further research should focus on the influence of mixed emerging pollutants on microalgal-bacterial symbiosis, and the feasibility of using selected emerging pollutants (e.g., antibiotics) as a carbon source for microalgal-bacterial symbiosis should also be explored. This review is expected to deepen our understandings on emerging pollutants removal from wastewater by microalgal-bacterial symbiosis.

Carbon sequestration performance, enzyme and photosynthetic activity, and transcriptome analysis of algae-bacteria symbiotic system after antibiotic exposure

Wastewater treatment technology based on algae-bacteria successfully combines pollutant purification, CO2 reduction and clean energy production to provide new insights into climate solutions. In this study, the reciprocal mechanisms between algae and bacteria were explored through physiological and biochemical levels of algae cells and differentially expressed genes (DEGs) based on the performance of immobilized algae-bacteria symbiotic particles (ABSPs) for CO2 fixation. The results showed that ABSPs promoted the CO2 fixation capacity of microalgae. The enhanced growth capacity and photosynthetic activity of algal cells in ABSPs are key to promoting CO2 uptake, and the stimulation of photosynthetic system and the promotion of Calvin cycle were the main contributors to enhanced carbon sequestration. These findings will provide guidance for carbon reduction using immobilized ABSS as well as deciphering the algae-bacteria reciprocal mechanism.

Shifting enzyme activity and microbial composition in sediment coregulate the structure of an aquatic plant community under polyethylene microplastic exposure

It has been shown that microplastics (MPs) interfere with critical biological processes (including development, growth and fitness); however, there is no information about the impact of MPs on plant productivity and community structure in freshwater ecosystems. Here, we investigated the effects of two sizes (MIC: 20-300 μm, MAC: 2-3 mm) and three concentrations (0.03 %, 0.3 %, and 0.6 %) of low-density polyethylene MPs on submerged plant communities. The results showed that plant responses to MPs were species specific, which can affect plant community structure. For canopy-forming species (Hydrilla verticillata), total biomass increased by 4 %-46 % and relative abundance increased by 23 %-34 % under MP exposure, while rosette-forming species (Vallisneria natans) decreased by 44 %-67 % in total biomass and relative abundance decreased by 54 %-71 %. Myriophyllum spicatum growth was largely unaffected by MPs. Community diversity was negatively correlated with MAC treatments, and the community root to shoot ratio decreased by 40 %, while community productivity increased by 41 % at a 0.6 % MAC concentration. Although MPs did not change the microbial community composition, alpha diversity was reduced at the 0.6 % concentration. It is worth noting that 0.6 % is a higher concentration than most field sediment investigations. During the experiment, the activity of functional enzymes related to carbon and nitrogen increased under most MP treatments. Structural equation modelling showed that MIC changed the community structure mainly by driving sediment enzyme activity, while MAC changed the community structure mainly by driving plant growth. The results implied that MPs may affect sediment enzymatic activities, microbial alpha diversity and aquatic plant growth, potentially altering the diversity and stability of aquatic ecosystems.

Effects of microplastics/nanoplastics on Vallisneria natans roots and sediment: Size effect, enzymology, and microbial communities

Microplastics/nanoplastics (MNPs) pollution in different environmental media and its adverse effects on organisms have received increasing attention from researchers. This paper compares the effects of natural concentrations of three different sizes (20 nm, 200 nm, and 2 μm) of MNPs on Vallisneria natans and sediments. MNPs with smaller sizes adhere more readily to V. natans roots, further promoting root elongation. In addition, the larger the particle size of MNPs, the higher the reactive oxygen species level in the roots, and the malondialdehyde level increased accordingly. In the sediment, 20 nm, and 200 nm MNPs increased the activity of related enzymes, including acid phosphatase, urease, and nitrate reductase. In addition, the dehydrogenase content in the treated sediments increased, and the content changes were positively correlated with the size of MNPs. Changes in microorganisms were only observed on the root surface. The addition of MNPs reduced the abundance of Proteobacteria and increased the abundance of Chloroflexi. In addition, at the class level of species composition on the root surface, the abundance of Gammaproteobacteria under the 20 nm, 200 nm, and 2 μm MNP treatments decreased by 21.19%, 16.14%, and 17.03%, respectively, compared with the control group, while the abundance of Anaerolineae increased by 44.63%, 26.31%, and 62.52%, respectively. These findings enhance the understanding of the size effects of MNPs on the roots of submerged plants and sediment.

Microplastics perturb nitrogen removal, microbial community and metabolism mechanism in biofilm system

Microplastics (MPs) are a significant component of global pollution and cause widespread concern, particularly in wastewater treatment plants. While understanding the impact of MPs on nutrient removal and potential metabolism in biofilm systems is limited. This work investigated the impact of polystyrene (PS) and polyethylene terephthalate (PET) on the performance of biofilm systems. The results revealed that at concentrations of 100 and 1000 μg/L, both PS and PET had almost no effect on the removal of ammonia nitrogen, phosphorus, and chemical oxygen demand, but reduced the removal of total nitrogen by 7.40-16.6%. PS and PET caused cell and membrane damage, as evidenced by increases in reactive oxygen species and lactate dehydrogenase to 136-355% and 144-207% of the control group. Besides, metagenomic analysis demonstrated both PS and PET changed the microbial structure and caused functional differences. Some important genes in nitrite oxidation (e.g. nxrA), denitrification (e.g. narB, nirABD, norB, and nosZ), and electron production process (e.g. mqo, sdh, and mdh) were restrained, meanwhile, species contribution to nitrogen-conversion genes was altered, therefore disturbing nitrogen-conversion metabolism. This work contributes to evaluating the potential risks of biofilm systems exposed to PS and PET, maintaining high nitrogen removal and system stability.

Potential effects of micro- and nanoplastics on phyllosphere microorganisms and their evolutionary and ecological responses

Plastic pollution is among the most urgent environmental and social challenges of the 21st century, and their influxes in the environment have altered critical growth drivers in all biomes, attracting global concerns. In particular, the consequences of microplastics on plants and their associated soil microorganisms have gained a large audience. On the contrary, how microplastics and nanoplastics (M/NPs) may influence the plant-associated microorganisms in the phyllosphere (i.e., the aboveground portion of plants) is nearly unknown. We, therefore, summarize evidence that may potentially connect M/NPs, plants, and phyllosphere microorganisms based on studies on other analogous contaminants such as heavy metals, pesticides, and nanoparticles. We show seven pathways that may link M/NPs into the phyllosphere environment, and provide a conceptual framework explaining the direct and indirect (soil legacy) effects of M/NPs on phyllosphere microbial communities. We also discuss the adaptive evolutionary and ecological responses, such as acquiring novel resistance genes via horizontal gene transfer and microbial degradation of plastics of the phyllosphere microbial communities, to M/NPs-induced threats. Finally, we highlight the global consequences (e.g., disruption of ecosystem biogeochemical cycling and impaired host-pathogen defense chemistry that can lead to reduced agricultural productivity) of altered plant-microbiome interactions in the phyllosphere in the context of a predicted surge of plastic production and conclude with pending questions for future research priorities. In conclusion, M/NPs are very likely to produce significant effects on phyllosphere microorganisms and mediate their evolutionary and ecological responses.