Microplastics Biofilms Research Articles

Enrichment Characteristics and Ecological Risk Prediction of Pathogens on Typical Microplastic Biofilms

As an emerging niche colonized by microorganisms, microplastics may selectively enrich pathogens, resulting in crucial ecological risks and potential threats to public health in aquatic environments. However, the enrichment characteristics and ecological risks of pathogens on different microplastic biofilms remain unclear. In this study, 16S rRNA high-throughput sequencing technology was used to investigate the differences in the bacterial community structure, occurrence characteristics of pathogens, and prediction of ecological risks on five typical microplastic biofilms of polyethylene （PE）, polypropylene （PP）, polystyrene （PS）, polyethylene terephthalate （PET）, and polyvinyl chloride （PVC） through a field in-situ incubation experiment. The results showed that after 28 d of in situ incubation, the macroscopic biofilms were formed on the surface of all microplastics, and the diversity and richness of the bacterial community on all microplastic biofilms were higher than in the surrounding water, indicating that the microorganisms in the surrounding water were selectively enriched on microplastics. Each type of microplastic biofilm had formed a unique bacterial community structure； in particular, PVC microplastics were more inclined to selectively enrich the members of Proteobacteria. A total of 47 human pathogens were identified using the HPB database, including six antibiotic resistance pathogens belonging to the lists of critical priority control. The number and total abundance of human pathogens detected on microplastic biofilm were higher than those in the surrounding water, and the dominant pathogens such as Bartonella, Burkholderia, and Brucella were selectively enriched on microplastic biofilms. Microbial phenotype prediction results based on BugBase showed that three functional phenotypes including biofilm formation, mobile element contained, and potentially pathogenic on microplastic biofilms had significantly increased by 2.38%-5.57%, 0.82%-7.13%, and 3.04%-8.30%, respectively, which were mainly contributed by α-Proteobacteria and γ-Proteobacteria. These results not only indicate that the selective enrichment of opportunistic pathogens on microplastic biofilms may lead to the increased risk of pathogenicity and antibiotic resistance co-spread but also provide reference for the accurate assessment of ecological risks caused by microplastic pollution in aquatic environments.

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.

Distinct microbial community structures formed on the biofilms of PLA and PP, influenced by physicochemical factors of sediment and polymer types in a 60-day indoor study

Microplastics (MPs) are colonized by biofilm-forming microbes. Biodegradable plastics, popular replacements for traditional plastics, still have unknown biofilm formation characteristics. We conducted a 60-day indoor experiment, where sediment was exposed to traditional MPs (polypropylene, PP), biodegradable MPs (polylactic acid, PLA), and glass beads (GLASS). The microbial communities in the MPs-biofilm were analyzed using high-throughput sequencing. Results indicated that Proteobacteria was the dominant phylum on all substrates, followed by Actinobacteria, and Firmicutes. At the genus level, the majority of microorganisms colonizing PP possessed nitrification and denitrification capabilities, while the dominant bacteria on PLA were capable of degrading lignin, cellulose and carbon metabolism. The genus Sphingomonas, a promising bacteria capable of degrading biodegradable microplastics, was particularly discovered on the PLA biofilm, meanwhile, bacterial colonization of PLA indirectly increased the potential for human transmission of pathogens. Redundancy analysis revealed that the pH and moisture significantly affected the bacterial communities. Pearson correlation heatmap indicated that the abundance of the majority of dominant bacterial genera of two MPs biofilms is negatively correlated with the physicochemical parameters of sediment (pH, moisture, TN, TP), except for salinity. The microbial communities associated with PP and PLA exhibited distinct differences caused by the combined effects of changes in physicochemical properties of sediment and different material substrates. This study provides further evidence of the significant selective features exhibited by microbial colonization on these two MPs when exposed to the same source community, offering insights into the exploration of promising bacteria for MPs degradation.

Quorum sensing regulating the heterogeneous transformation of antibiotic resistance genes in microplastic biofilms

Microplastics (MPs) provide a specific habitat for bacterial adhesion and the adsorption of extracellular DNA (eDNA), making them hotspots for the transformation of antibiotic resistance genes (ARGs) in the environment. However, the heterogeneous mechanism of ARG regulation by quorum sensing (QS) in MP biofilms remains unclear. This study demonstrated that QS signals, including C8-HSL, 3-oxo-C10-HSL, and C12-HSL, were detected at ng/L levels in Bacillus subtilis biofilms colonized on MPs. The addition of these three AHLs enhanced natural transformation by 1–2 orders of magnitude in both MP and natural substrate (NS) biofilms, while QS inhibitors decreased transformation frequencies by 2 orders of magnitude. Moreover, transformation frequencies in MP biofilms increased 6.0-fold under QS regulation mediated by AHLs, compared to a 2.5-fold increase in NS biofilms. QS-regulated biofilm formation and EPS secretion were found to be responsible for ARG dissemination in MP biofilms, as indicated by the positive correlation between transformation frequencies and EPS variation. Additionally, mRNA expression analysis revealed that activation and inhibition of the QS system in MP biofilms regulated the expression of natural transformation-related genes, including epsG (regulating EPS secretion) and recO (regulating eDNA transformation). These results highlight the significant influence of the QS system on ARG dissemination through heterogeneous biofilm formation and EPS secretion in MP biofilms. Understanding the effect and mechanism of QS on ARG natural transformation provides new insights into controlling ARG spread by targeting QS in host bacteria within MP biofilms.

Comprehensive assessment of chlorination disinfection on microplastic-associated biofilms

Chlorination on microplastic (MP) biofilms was comprehensively investigated with respect to disinfection efficiency, morphology, and core microbiome. The experiments were performed under various conditions: i) MP particles; polypropylene (PP) and polystyrene (PS), ii) MP biofilms; Escherichia coli for single-species and river water microorganisms for multiple-species, iii) different chlorine concentrations, and iv) different chlorine exposure periods. As a result, chlorination effectively inactivated the MP biofilm microorganisms. The disinfection efficiency increased with increasing the free chlorination concentration and exposure periods for both single- and multiple-species MP biofilms. The multiple-species MP biofilms were inactivated 1.3–6.0 times less than single-species MP biofilms. In addition, the PP-MP biofilms were more vulnerable to chlorination than the PS-MP biofilms. Morphology analysis verified that chlorination detached most MP biofilms, while a small part still remained. Interestingly, chlorination strongly changed the biofilm microbiome on MPs; the relative abundance of some microbes increased after the chlorination, suggesting they could be regarded as chlorine-resistant bacteria. Some potential pathogens were also remained on the MP particles after the chlorination. Notably, chlorination was effective in inactivating the MP biofilms. Further research should be performed to evaluate the impacts of residual MP biofilms on the environment.

Characterization and tolerance of foodborne pathogenic bacteria in microplastic biofilm

Microplastics have the ability to selectively accumulate microorganisms from their surrounding environments, leading to the formation of biofilms. The potential for microplastic biofilm in food processing environments to contaminate the processing environment and food matrices poses a threat to food safety. This study validated the biofilm formation of three commonly encountered foodborne pathogens, Salmonella enterica serovar Typhimurium (ST), Staphylococcus aureus (SA), and Listeria monocytogenes (LM) on microplastics, and investigated their tolerance to disinfectant and gastrointestinal tract. Three strains showed distinct biofilm formation patterns, with biomass reaching a steady state at 2 d. Meanwhile, the particle size of microplastics exhibited a specific impact on biofilm formation, with smaller microplastics sizes leading to increased biofilm formation. Sodium hypochlorite (NaClO) can effectively eliminate most biofilm-forming bacteria, except for ST. After treatment with 50 ppm NaClO, 34% cells in ST biofilm survived. Only SA survived in simulated gastric fluid, with around 3 log reduction after 1 h. ST and LM were not detected. All three strains showed a slight increase after treatment with simulated intestinal fluid for 6 h. These results highlighted the capacity of microplastics to transport pathogens through biofilms, emphasizing the potential synergistic effects between microplastics and pathogens in food-associated environments.

Growth and Cell Size of Microalga Auxenochlorella protothecoides AS-1 under Different Trophic Modes.

Certain microalgal species can grow with different trophic strategies depending on the availability of nutrient resources. They can use the energy from light or an organic substrate, or both, and can therefore be called autotrophs, heterotrophs, or mixotrophs. We recently isolated a microalgal strain from the microplastic biofilm, which was identified as Auxenochlorella protothecoides, AS-1. Strain AS-1 grew rapidly in bacterial culture media and exhibited different growth rates and cell sizes under different trophic conditions. We compared the growth performance of AS-1 under the three different trophic modes. AS-1 reached a high biomass (>4 g/L) in 6 days under mixotrophic growth conditions with a few organic carbons as a substrate. In contrast, poor autotrophic growth was observed for AS-1. Different cell sizes, including daughter and mother cells, were observed under the different growth modes. We applied a Coulter Counter to measure the size distribution patterns of AS-1 under different trophic modes. We showed that the cell size distribution of AS-1 was affected by different growth modes. Compared to the auto-, hetero- and mixotrophic modes, AS-1 achieved higher biomass productivity by increasing cell number and cell size in the presence of organic substrate. The mechanisms and advantages of having more mother cells with organic substrates are still unclear and warrant further investigations. The work here provides the growth information of a newly isolated A. protothecoides AS-1 which will be beneficial to future downstream applications.

Size effects of microplastics on antibiotic resistome and core microbiome in an urban river

Microplastics (MPs) in aquatic environments provide a new ecological niche that facilitates the attachment of antibiotic-resistance genes (ARGs) and pathogens. However, the effect of particle size on the colonization of antibiotic resistomes and pathogens remains poorly understood. To address this knowledge gap, this study explored the antibiotic resistome and core microbiome on three distinct types of MPs including polyethylene, polypropylene, and polystyrene (PS), with varying sizes of 30, 200, and 3000 μm by metagenomic sequencing. Our finding showed that the ARG abundances of the PS type increased by 4-folds with increasing particle size from 30 to 3000 μm, and significant differences in ARG profiles were found across the three MP types. In addition, the concentrations of ARGs and mobile genetic elements (MGEs) were markedly higher in the MPs than in the surrounding water, indicating their enrichment at these artificial interfaces. Notably, several pathogens such as Pseudomonas aeruginosa, Mycobacterium tuberculosis, and Legionella pneumophila were enriched in MP biofilms, and the co-occurrence of ARGs and virulence factor genes (VFGs)/MGEs suggested the presence of pathogenic antibiotic-resistant microbes with potential mobility. Both redundancy analysis (RDA) and structural equation modeling (SEM) demonstrated that physicochemical properties such as zeta potential, MP size, and contact angle were the most significant contributors to the antibiotic resistome. Strikingly, no significant differences were observed in the health risk scores of the ARG profiles among different sizes and types of MPs. This study expands our knowledge on the impact of MP size on microbial risks, thus enhancing our understanding of the potential health hazards they pose.

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.

The bioaccessibility of adsorped heavy metals on biofilm-coated microplastics and their implication for the progression of neurodegenerative diseases.

Microplastic (MP) tiny fragments (< 5mm) of conventional and specialized industrial polymers are persistent and ubiquitous in both aquatic and terrestrial ecosystem. Breathing, ingestion, consumption of food stuffs, potable water, and skin are possible routes of MP exposure that pose potential human health risk. Various microorganisms including bacteria, cyanobacteria, and microalgae rapidly colonized on MP surfaces which initiate biofilm formation. It gradually changed the MP surface chemistry and polymer properties that attract environmental metals. Physicochemical and environmental parameters like polymer type, dissolved organic matter (DOM), pH, salinity, ion concentrations, and microbial community compositions regulate metal adsorption on MP biofilm surface. A set of highly conserved proteins tightly regulates metal uptake, subcellular distribution, storage, and transport to maintain cellular homeostasis. Exposure of metal-MP biofilm can disrupt that cellular homeostasis to induce toxicities. Imbalances in metal concentrations therefore led to neuronal network dysfunction, ROS, mitochondrial damage in diseases like Alzheimer's disease (AD), Parkinson's disease (PD), and Prion disorder. This review focuses on the biofilm development on MP surfaces, factors controlling the growth of MP biofilm which triggered metal accumulation to induce neurotoxicological consequences in human body and stategies to reestablish the homeostasis. Thus, the present study gives a new approach on the health risks of heavy metals associated with MP biofilm in which biofilms trigger metal accumulation and MPs serve as a vector for those accumulated metals causing metal dysbiosis in human body.

Microplastics enrichment characteristics of antibiotic resistance genes and pathogens in landfill leachate

Microplastics (MPs) pollution is a pressing environmental issue for aquatic ecosystems. Landfill leachate is an important contributor of MPs and antibiotic resistant genes (ARGs). However, there are few studies on the colonization of ARGs and pathogens on MPs in leachate. This study conducted incubation experiments with polyethylene terephthalate (PET) and polypropylene (PP) MPs in landfill leachate which were about 3–5 years old (PL) and 5–10 years old (AL). After incubation, the bacterial cells colonized and grew on the surface of MPs, inducing the increase of oxygenated oxygen functional groups (e.g., hydroxyl, carbonyl) on the MPs surface. Real-time PCR indicated that MPs selectively enriched ARGs, such as genes tetM, tetC, mcr-1, aac(6′)-Ib-cr, blaTEM and blaSHV in leachate. The diversity of bacterial communities on MPs was significantly increased in AL leachate, but decreased in PL leachate. The differences in bacterial communities in MPs biofilms were related to the type of MPs. Compared with AL leachate, the abundance of Chloroflexi increased by 15.7% on the PET, and the abundance of Acidobacteriota increased by 6.23 fold on the PP. The abundance of Firmicutes increased from 20.7% in PL leachate to 65.8% and 60.7% on PET and PP, respectively. Additionally, pathogens were observed to be more abundant on MPs compared to leachate. In particular, pathogens (Staphylococcus, Streptococcus, Enterobacter and Rhodococcus) associated with sul1 and sul2 were generally present at higher levels on MPs than in the surrounding leachate. These results provide significant implications for understanding the health risk of MPs in the environment.

Microplastic biofilm: An important microniche that may accelerate the spread of antibiotic resistance genes via natural transformation

Microplastic (MP) biofilms provide a specific microniche for microbial life and are a potential hotspot for the horizontal gene transfer (HGT) of antibiotic resistance genes (ARGs). Nevertheless, the acquisition of ARGs in MP biofilms via natural transformation mediated by extracellular DNA (eDNA) has been rarely explored. This study demonstrated that MP biofilms promoted the natural transformation of extracellular ARGs at the single-cell and multi-species levels, compared to natural substrate (NS) biofilms and bacterioplankton. The transformation frequency on MP biofilms was up to 1000-fold compare to that on NS. The small MPs and aged MPs enhanced the ARG transformation frequencies up to 77.16-fold and 32.05-fold, respectively, compared with the large MPs and pristine MPs. The transformation frequencies on MP biofilms were significantly positively correlated with the bacterial density and extracellular polymeric substance (EPS) content (P < 0.05). Furthermore, MPs significantly increased the expression of the biofilm formation related genes (motA and pgaA) and DNA uptake related genes (pilX and comA) compared to NS and bacterioplankton. The more transformants colonized on MPs contributed to the enhanced transformation frequencies at the community-wide level. Overall, eDNA-mediated transformation in MP biofilms may be an important path of ARG spread, which was promoted by heterogeneous biofilm.

Biofilm formation on polyethylene microplastics and their role as transfer vector of emerging organic pollutants.

Microplastic (MP)-colonizing microorganisms are important links for the potential impacts on environmental, health, and biochemical circulation in various ecosystems but are not yet well understood. In addition, biofilms serve as bioindicators for the evaluation of pollutant effects on ecosystems. This study describes the ability of three polyethylene-type microplastics, white (W-), blue (B-), and fluorescent blue (FB-) MPs, to support microbial colonization of Pseudomonas aeruginosa, the effect of mixed organic contaminants (OCs: amoxicillin, ibuprofen, sertraline, and simazine) on plastic-associated biofilms, and the role of biofilms as transfer vectors of such emerging pollutants. Our results showed that P. aeruginosa had a strong ability to produce biofilms on MPs, although the protein amount of biomass formed on FB-MP was 1.6- and 2.4-fold higher than that on B- and W-MP, respectively. When OCs were present in the culture medium, a decrease in cell viability was observed in the W-MP biofilm (65.0%), although a general impairing effect of OCs on biofilm formation was ruled out. Microbial colonization influenced the ability of MPs to accumulate OCs, which was higher for FB-MP. In particular, the sorption of amoxicillin was lower for all bacterial-colonized MPs than for the bare MPs. Moreover, we analysed oxidative stress production to assess the impact of MPs or MPs/OCs on biofilm development. The exposure of biofilms to OCs induced an adaptive stress response reflected in the upregulation of the katB gene and ROS production, particularly on B- and FB-MP. This study improves our understanding of MP biofilm formation, which modifies the ability of MPs to interact with some organic pollutants. However, such pollutants could hinder microbial colonization through oxidative stress production, and thus, considering the key role of biofilms in biogeochemical cycles or plastic degradation, the co-occurrence of MPs/OCs should be considered to assess the potential risks of MPs in the environment.

Aging microplastic aggravates the pollution of heavy metals in rhizosphere biofilms

Heavy metals (HMs) and microplastics (MPs) are ubiquitous in agricultural soils. Rhizosphere biofilms are important sites for HM adsorption, and biofilms are easily disturbed by soil MPs. However, the adsorption of HMs on rhizosphere biofilms induced by aged MPs is not clear. In this study, the adsorption behavior of Cd(II) on biofilms and pristine/aged polyethylene (PE/APE) was analyzed and quantified. The results showed that the adsorption amount of Cd(II) on APE was greater than that on PE, in which the oxygen-containing functional groups of APE could provide binding sites to increase the adsorption of HMs. Density functional theory (DFT) calculations revealed that the binding energy of Cd(II) onto APE (−6.00 kcal·mol-1) was much stronger than that of PE (7.11 kcal·mol-1) due to hydrogen bonding interactions and oxygen atom-metal interactions. For HM adsorption on MP biofilms, APE increased the adsorption capacity of Cd(II) by 4.7 % relative to PE. The pseudo-second-order kinetic and Langmuir models suitably described the adsorption kinetics and isothermal adsorption of Cd(II), respectively (R2 > 80 %), indicating that monolayer chemisorption dominated. However, the hysteresis indices of Cd(II) in the Cd(II)-Pb(II) system (< 1) were higher than those in the single system (> 1) due to the competitive adsorption of HMs. Overall, this study clarifies the effect of MPs on the adsorption of HMs in rhizosphere biofilms and will help researchers assess the ecological risks of HMs in soils.

Microplastic biofilm, associated pathogen and antimicrobial resistance dynamics through a wastewater treatment process incorporating a constructed wetland

Microplastics in wastewater are colonized by biofilms containing pathogens and antimicrobial resistance (AMR) genes that can be exported into receiving water bodies. This study investigated establishment and changes in microplastic-associated biofilm and AMR during a conventional full-scale 2100 population equivalent wastewater treatment process combined with a free water surface polishing constructed wetland. Sequential microplastic colonization experiments were conducted at different stages of the wastewater treatment process, including in raw sewage, treated effluent and the constructed wetland. Two scenarios were tested in which the constructed wetland served as either (i) a polishing step or (ii) as primary recipient of sewage inoculated microplastics. Bacterial 16S rRNA gene sequencing was carried out for qualitative bacterial community analysis. qPCR was applied for quantitative analysis of AMR genes (sul1, ermB, tetW, intiI1), bacterial biomass (16S rRNA) and a human fecal marker (HF183). Microbial diversity on microplastics increased with incubation time. The initial sewage-derived biofilm composition changed more significantly in the wastewater effluent compared to the constructed wetland. Pathogen and AMR load decreased by up to two orders of magnitude after coupled conventional and constructed wetland treatment, while less impact was observed when sewage-inoculated microplastic material was directly transferred into the constructed wetland. Aeromonas, Klebsiella, and Streptococcus were key pathogenic genera correlated with AMR in microplastic-associated biofilms. Despite decreasing trends on human pathogens and AMR load along the treatment process, microplastic-associated biofilms were a considerable potential hotspot for AMR (intI1 gene) and accommodated Cyanobacteria and fish pathogens.

Microplastics influence the fate of antibiotics in freshwater environments: Biofilm formation and its effect on adsorption behavior.

Microplastics (MPs) are substrates available for biofilms colonization in natural water environments. The biofilms formation may enhance the ability of MPs to adsorb harmful contaminants. Herein, we investigated the biofilms formation of three different MPs (PVC, PA and HDPE) in simulated natural environment, and observed the chemical structure, charge property, hydrophobicity and other properties of MPs affect microbial biomass and community composition. More importantly, potential pathogens were found in all three MPs biofilms. Furthermore, the adsorption capacities of original MPs and biological aging MPs for norfloxacin (NOR) was compared. HDPE has the largest adsorption capacity for NOR, while PA has the smallest adsorption capacity for NOR. It was concluded that the formation of biofilms enhanced the adsorption of NOR by 50.60 %, 24.17 % and 46.02 % for PVC, PA and HDPE, respectively. In addition, hydrogen-bond interaction, electrostatic interaction and hydrophobic interaction were found to dominate the adsorption of NOR by MPs. Our study contributed to improve the understanding of the interactions between aging MPs and contaminants in the natural water environments, and provided essential information for ecological risk assessment of MPs.

Impacts of hydraulic conditions on microplastics biofilm development, shear stresses distribution, and microbial community structures in drinking water distribution pipes

Both microplastic and biofilm are contamination sources in drinking water, but their integrated impacts on water quality have been rarely studied, especially in drinking water distribution pipes with complex hydraulic conditions. This study explored the impacts of hydraulic conditions (0–2 m/s) on microplastic biofilm (MP-BM) development, shear stresses distribution, and microbial community structures. The research was conducted for two weeks using a pilot test device to simulate practical water pipes. The following were the primary conclusions: (1) According to morphology analysis, clusters (>5 μm) significantly increased in the plastisphere when the flow velocity ranged from 0.55 m/s to 0.95 m/s, and average size of clusters decreased when the flow velocity ranged from 1.14 m/s to 1.40 m/s (2) Characteristics of MP-BM impact shear stress on both plastisphere and pipe wall biofilm. Shear stresses were positively correlated with flow velocity, number of MP-BM, and size of MP-BM, while negatively correlated with diameters of pipes. (3) 31 genera changed strictly and monotonously with the fluid velocity, accounting for 15.42%. Opportunistic pathogens in MP-BM such as Sediminibacterium, Curvibacter, and Flavobacterium were more sensitive to hydraulic conditions. Moreover, microplastics (<100 μm) deserve more attention to avoid human ingestion and to prevent mechanical damage and bio-chemical risks.

Growth and prevalence of antibiotic-resistant bacteria in microplastic biofilm from wastewater treatment plant effluents

It is accepted that Microplastic (MP) biofilms accumulates antibiotic-resistant bacteria (ARB) and antibiotic-resistant genes (ARGs) in water. ARB/ARGs and MPs are emerging pollutants of concern due to various associated health risks. The objective of this study was to 1) investigate the ARB community in a pilot-scale wastewater treatment plant (WWTP) effluent, 2) to study and visualize the ARB/ARGs in MP biofilm grown in WWTP effluent and tap water, and 3) to analyze microplastic adherent ARB/ARGs in the biofilm and planktonic ARB/ARGs in the filtrate under controlled conditions. Results indicated the dominance of Pseudomonas, Aeromonas, and Bacillus among isolated ARB in WWTP effluent. Representative resistance strains were incubated in 300 mL water containing commercial polystyrene beads of 300550 μm diameter (MP) in a series of batch experiments. Microbiological, molecular, and microscopic analyses were performed by enumeration, 16srRNA, real-time polymerase chain reaction (qPCR), and Field Emission-Scanning Electron Microscopy (FEG-SEM) techniques. The analyzed viable ARB indicated an increasing trend in MP biofilms between days 3 and 5. It further decreased on days 7 and 9. The prevalence of ARB in the filtrate and MP biofilm varied as a function of time and TOC level, while no significant impacts were observed for minor temperature variation, low antibiotic pressure, and increased MP mass with few exceptions. Relative abundance of ARGs (vanA, sul1) and integron integrase gene (intl1) in MP biofilm were significantly different across different TOC levels, time, and antibiotic pressure. ARGs and intl1 were detected in the MP biofilm in tap water and WWTP effluent on day 30.

Interactive impacts of microplastics and chlorine on biological stability and microbial community formation in stagnant water

Possibility of human exposure to microplastics (MPs) in water environment has been escalating, and subsequent challenges of MPs to biostability and biosafety in drinking water deserve more attention, especially in stagnant water. The present study explored the integrated impacts of MPs and chlorine on disinfection kinetics, microbial growth, and microbial community formation in drinking water, by setting MPs or microplastic-biofilm (MP-BM) under different disinfection conditions. The following were the primary conclusions: (1) The presence of MP and MP-BM led to the deterioration of water indices (especially turbidity) when chlorine was less than 1 mg/L. (2) MP/MP-BM accelerated the decay of disinfectants and MP-BM consumed more rapidly. Meanwhile, chlorine contributed to the level of BRP, ranging from 4.78 × 105 CFU/mL to 1.42 × 107 CFU/mL. (3) MP/MP-BM and chlorine integrally shaped microbial communities in water samples and biofilm samples. Microbial dissimilarity between isolated and hybrid MP-BM indicated manners of microbial field or non-contact communication. Microbial abundance and OPs were effectively controlled when chlorine was over 1 mg/L. (4) According to time-lag differential equations simulation, impulsive chlorination contributed to controlling microbial risks and DBPs induced by MP/MP-BM and water stagnation.

Biofilm Structural and Functional Features on Microplastic Surfaces in Greenhouse Agricultural Soil

Microplastics (MPs) enter the soil through a variety of pathways, including plastic mulching, sludge, and organic manure application. In recent years, domestic and foreign experts and scholars have been concerned about the residues and contamination of MPs in the soil of greenhouse agriculture. In this investigation, five types of MPs including low-density polyethylene (LDPE), high-density polyethylene (HDPE), polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET), and two concentrations (1% and 5%, w/w) were used in a 30-day external exposure test. Evidence of microbial enrichment was found on the surface of the MPs. The total amount of biofilm on the surface of MPs increased dramatically with increasing exposure time and MP concentrations. The polysaccharide content of extracellular polymers (EPS) in biofilms was significantly different, and the maximum PS1 (1% (w/w) PS) concentration was 50.17 mg/L. However, EPS protein content did not change significantly. The dominant bacteria on the surface of MPs with different types and concentrations were specific, and the relative abundance of Patescibacteria was significantly changed at the phylum level. At the genus level, Methylophaga, Saccharimonadales, and Sphingomonas dominated the flora of LDPE1 (1% (w/w) LDPE), PS1, and PET5 (5% (w/w) PET). The dominant bacteria decompose organic materials and biodegrade organic contaminants. According to the FAPROTAX functional prediction study, chemoheterotrophy and aerobic chemoheterotrophyplay a role in ecosystem processes such as carbon cycle and climate regulation. The application of LDPE1 has a greater impact on the carbon cycle. Plant development and soil nutrients in greenhouse agriculture may be influenced by the interaction between MPs and microorganisms in the growing area, while MP biofilms have an impact on the surrounding environment and pose an ecological hazard.