Presence of polyethylene terephthalate (PET) fibers in hyporheic zone alters colonization patterns and seasonal dynamics of biofilm metabolic functioning

Short-term exposure to triclocarban alters microbial community composition and metabolite profiles in freshwater biofilms

Triclocarban (TCC), an emerging contaminant in water environments, its effects on freshwater biofilms remain insufficiently understood. This study investigates the effects of TCC exposure (at concentrations of 10 μg L-1 and 10 mg L-1) on mature freshwater biofilms. TCC was found to inhibit biofilm activity as evidenced by changes in surface morphology and the ratio of live/dead cells. Moreover, both concentrations of TCC were observed to modify the structure of the biofilm community. Metabolomics analysis revealed an overlap in the toxicity mechanisms and detoxification strategies triggered by various concentrations of TCC in biofilms. However, the higher toxicity induced by 10 mg L-1 TCC resulted from the downregulation of proline betaine, disrupting the homeostasis of cellular osmotic pressure regulation in biofilms. Notably, lipid and lipid-like molecules showed high sensitivity to different concentrations of TCC, indicating their potential as biomarkers for TCC exposure. Annotation of the differential metabolites by KEGG revealed that alterations in amino acid and carbon metabolism constituted the primary response mechanisms of biofilms to TCC. Moreover, the biofilm demonstrated enhanced nucleic acid metabolism, which bolstered resistance against TCC stress and heightened tolerance. Furthermore, elevated TCC concentrations prompted more robust detoxification processes for self-defense. Overall, short-term exposure to TCC induced acute toxicity in biofilms, yet they managed to regulate their community structure and metabolic levels to uphold oxidative homeostasis and activity. This research contributes to a deeper comprehension of TCC risk assessment and policy control in aquatic environments.

Microplastics alter the microbiota-mediated phosphorus profiles at sediment-water interface: Distinct microbial effects between sediment and plastisphere

Microplastics (MPs) are ubiquitous in freshwater sediments, raising concern about their potential impacts on ecosystem services. However, the specific impacts of microbiota mediated by MPs in sediment and plastisphere compartments on P availability remain elusive. This investigation conducted a series of microcosm experiments utilizing eutrophic lake sediment amended with fuel-based polyethylene terephthalate (PET), bio-based polylactic acid (PLA) MPs, and a natural cobblestone substrate to unravel their effects. The findings highlighted that MPs induced alterations in bacterial communities in both sediment and plastisphere, consequently modifying P availabilities at the sediment-water interface (SWI). In comparison to non-biodegradable PET, biodegradable PLA MPs presented higher proportions of specific bacteria and functional genes associated with P profiles, such as Firmicutes, Ignavibacteriota, and P mineralizing genes in the sediment and plastisphere. This, in turn, elevated the levels of soluble reactive P in the porewater by 54.19 % (0-1 cm), 55.81 % (1-3 cm), and 18.24 % (3-5 cm), respectively. Additionally, PLA obviously altered P immobilization capacity and bioavailability, increasing the organic P fraction. Whereas, inert cobblestone exhibited negligible influence on P biogeochemical processes during the incubation. Moreover, the biofilm communities and those in the surrounding sediment specifically contributed to the changes in P profiles at the SWI. The functional genes associated with P profiles in the sediment mainly concentrate on P mineralization and P uptake/transport. In the plastisphere, P activation genes are obviously affected under MP exposure. This study fills the knowledge gap concerning the repercussions of MPs on ecosystem services.

Photo-oxidation of Micro- and Nanoplastics: Physical, Chemical, and Biological Effects in Environments

Micro- and nanoplastics (MNPs) are attracting increasing attention due to their persistence and potential ecological risks. This review critically summarizes the effects of photo-oxidation on the physical, chemical, and biological behaviors of MNPs in aquatic and terrestrial environments. The core of this paper explores how photo-oxidation-induced surface property changes in MNPs affect their adsorption toward contaminants, the stability and mobility of MNPs in water and porous media, as well as the transport of pollutants such as organic pollutants (OPs) and heavy metals (HMs). It then reviews the photochemical processes of MNPs with coexisting constituents, highlighting critical factors affecting the photo-oxidation of MNPs, and the contribution of MNPs to the phototransformation of other contaminants. The distinct biological effects and mechanism of aged MNPs are pointed out, in terms of the toxicity to aquatic organisms, biofilm formation, planktonic microbial growth, and soil and sediment microbial community and function. Furthermore, the research gaps and perspectives are put forward, regarding the underlying interaction mechanisms of MNPs with coexisting natural constituents and pollutants under photo-oxidation conditions, the combined effects of photo-oxidation and natural constituents on the fate of MNPs, and the microbiological effect of photoaged MNPs, especially the biotransformation of pollutants.

Microbial co-culture mediated by intercellular nanotubes during DMAC degradation: Microbial interaction, communication mode, and degradation mechanism

Microbial co-culture has been proven as an effective technique for environmental remediation. In this study, co-culture mechanism of Rhodococcus ruber HJM-8 and Paracoccus communis YBH-X during N,N-dimethylacetamide (DMAC) degradation was studied. The comparison of degradation performance in monoculture and co-culture was presented; due to the efficient cooperation between the two strains via parallel and cascaded degradation, the removal efficiency of total nitrogen (TN) in co-culture could reach 90.1%, which was 1.35 and 1.21 times higher than that of HJM-8 and YBH-X, respectively. Then the communication mode of co-culture during DMAC degradation was determined as contact-independent and contact-dependent interactions between microorganisms. Meanwhile, intercellular nanotube between HJM-8 and YBH-X was found as a unique contact-dependent interaction. The cell staining experiments and RNA sequencing analyses revealed that the nanotube could be used as a bridge to exchange cytoplasmic molecules, and thus improved material transfer and enhanced cell connection in co-culture. The results of KEGG pathway showed that differentially expressed genes in co-culture have an association with cell metabolism, nanotube generation, and genetic material transfer. Furthermore, a mechanism diagram of DMAC biodegradation was proposed for co-culture, indicating that bidirectional cooperation was established between HJM-8 and YBH-X which was mediated by the conversions of acetate and nitrogen. Finally, the co-culture system was validated for treatment of an actual wastewater; results indicated that removal efficiencies of 100% and 68.2% were achieved for DMAC and TN, respectively, suggesting that co-culture had the potential for application.

Polystyrene microplastics-induced macrophage extracellular traps contributes to liver fibrotic injury by activating ROS/TGF-β/Smad2/3 signaling axis

Microplastics (MPs) are a type of emerging pollutant, posing a great threat to human and animal health. While recent studies have revealed the link between MPs exposure and liver injury of organisms, the effect of particle size on the level of MPs-induced hepatotoxicity and the intrinsic mechanism remain to be explored. Here, we established a mouse model exposed to two-diameter polystyrene MPs (PS-MPs, 1-10 μm or 50-100 μm) for 30 days. The in vivo results revealed that PS-MPs caused liver fibrotic injury in mice, accompanied with macrophages recruitment and macrophage extracellular traps (METs) formation, which were negatively correlated with particle size. The data in vitro showed that PS-MPs treatment could induce macrophages to release METs in a reactive oxygen species (ROS)-independent manner, and the METs formation level caused by large-size particles was higher than small-size particles. Further mechanistic analysis of a cell co-culture system revealed that PS-MPs-induced METs release led to a hepatocellular inflammatory response and epithelial-mesenchymal transition (EMT) via activating the ROS/TGF-β/Smad2/3 signaling axis, and this biological crosstalk could be relieved by DNase I. Overall, this findings demonstrates the key role of the action mechanism of METs in aggravating MPs-caused liver injury.

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.

Mangrove degradation retarded microplastics weathering and affected metabolic activities of microplastics-associated microbes

Currently, information on microplastics (MPs) weathering characteristics and ecological functions driven by MPs-associated microbes in mangrove ecosystems remains unclear, especially in the degraded areas. Herein, we compared the weathering characteristics of MPs in both undegraded and degraded mangrove sediments, and then explored the potential interactions between their weathering characteristics and microbially-driven functions. After 70 days of incubation, different MPs (including polyethylene PE, polystyrene PS, and polylactic acid PLA) were strongly weathered in mangrove sediments, with significant erosion features. Interestingly, more obvious weathering characteristics were found for MPs in the undegraded mangrove sediments. O/C ratio value of MPs in the undegraded sediments was 2.3-3.0 times greater than that in the degraded ones. Besides, mangrove degradation reduced network complexity among MPs-associated microorganisms and affected their metabolic activities. Bacteria involved in carbon cycle process enriched on nondegradable MPs, whereas abundant bacteria responsible for sulphur cycle were observed on PLA-MPs. Moreover, these relevant bacteria were more abundant on MPs in the undegraded mangrove sediments. Mangrove degradation could directly and indirectly affect MPs weathering process and microbially-driven functions through regulating sediment properties and MPs-associated microbes. During weathering, contact angle and roughness of MPs were key factors influencing the colonisation of hydrocarbon degradation bacteria on MPs.

Formation of Nano- and Microplastics and Dissolved Chemicals During Photodegradation of Polyester Base Fabrics with Polyurethane Coating

Polyurethane (PU) synthetic leathers possess an intricate plastic composition, including polyester (PET) base fabrics and upper PU resin, but the release of fragments from the complexes is unclear. Therefore, we investigated the photodegradation trends of PET base fabrics with PU coating (PET-U) as a representative of composite plastics. Attention was paid to the comparison of the photoaging process of PET-U with that of pure PET base fabric (PET-P). To reveal the potential for chain scission, physical and chemical changes (e.g., surface morphology, molecular weight, and crystallinity) of the two fabrics were explored. The generation of microplastic fibers (MPFs) and microplastic particles (MPPs) was distinguished. Compared with PET-P, PET-U showed a similar but delayed trend in various characteristics and debris release rate as the photoaging time prolonged. Even so, after 360 h of illumination, the generated number of MPs (including MPFs and MPPs) rose considerably to 9.32 × 10⁷ MPs/g, and the amount of released nanoplastics (NPs) increased to 2.70 × 10¹¹ NPs/g from PET-U. The suppression of MP formation from PET-U was potentially directed by the physical shielding of the upper PU layer and the dropped MPs, which resisted the photochemical radical effect. The components of dissolved organic matter derived from plastics (P-DOM) were separated by molecular weight using a size-exclusion chromatography-diode array detector-organic carbon detector/organic nitrogen detector (SEC-DAD-OCD/OND), and the results showed that a larger amount of carbon- and nitrogen-containing chemical substances were generated in PET-U, accompanied by more aromatic and fluorescent compounds. The results provided theoretical bases and insights for future research on the risks of plastic debris from PU synthetic leathers on aquatic organisms and indicated feasible directions for exploring combined pollution studies of plastics.

Investigating the effects of biodegradable microplastics and copper ions on probiotic (Bacillus amyloliquefaciens): Toxicity and application

Currently, microplastic pollution is more serious and complicates the toxic effects of other co-existing pollutants in the environment. However, the effect and mechanism of biodegradable plastics on the growth and metabolism of probiotic remain unclear. This work selected Bacillus amyloliquefaciens as model bacterium for a three-day exposure experiment to probe the issues. The results showed that 100 mg/L polylactic acid microplastics (PLA MPs) (3-4 mm, flake shape) caused oxidative damage to cell membranes, disrupted cell wall composition and inhibited cell growth by 21.2-27.5 %. The toxicity was not simply additive or synergistic effects when PLA MPs (100 mg/L) and copper ions (10 mg/L) coexisted. PLA MPs did not significantly increase the toxicity of copper to bacteria, instead triggered some mechanisms to resist the toxicity of copper. The bacteria formed spores to resist PLA MPs, while the copper ions toxicity was weaken by chelation and efflux. It is worth noting that copper ions instead increased the expression of genes related fengycin and iturin then improving the bacteriostatic activity of the probiotic. This paper deeply analyzes the toxicity mechanism of combined pollution on Bacillus amyloliquefacien, and also provides new perspective for helping to inhibit pathogenic bacteria under biodegradable microplastics and metal stress.