Marine Microbial Assemblages on Microplastics: Diversity, Adaptation, and Role in Degradation

The impact of polyvinyl chloride microplastics on carbon and nitrogen cycling in peat-forming environments: relevance of the filler additive calcium carbonate (CaCO3)

Peat-forming wetlands (PFW) are crucial in the global C-cycle, yet they are increasingly threatened by various anthropogenic pressures, including microplastic (MP) pollution. We investigate the impacts of polyvinyl chloride (PVC) and its additive, calcium carbonate (CaCO3) on organic matter (OM) degradation in PFW. We conducted two experiments: first, by mixing peat soil with increasing concentrations of crushed sanitary PVC-MP (0.3 %, 3 %, and 30 %) and second, by assessing the role of CaCO₃ in modulating these impacts. Our findings revealed significant alterations in peat chemical properties largely mediated by CaCO3 (i.e. increased pH, and Ca2+, Mg2+, K+ concentrations). PVC-MP increased carbon dioxide (CO2) and methane (CH4) production, as well as dissolved organic carbon release. CaCO3 may have enhanced CO2 release through its dissolution and contributed to CH4 production as a C source for a more diverse and active methanogenic community (higher mcrA gene abundance). Shifts in microbial community composition (e.g. reduction of Acidobacteriae and increase in active fermenters, such as Clostridia) and metabolism (higher lignin-like compounds degradation and P-uptake activity but lower activity of labile-C degrading enzymes) also contributed in the C-cycle alterations. PVC-MP enhanced denitrification (narG gene abundance) but reduced relative proportion of the ammonia-oxidizing archaea Nitrososphaeria, leading to inhibition of nitrification. The effects of PVC-MP were concentration-dependent, with CaCO₃ strongly influencing on the C cycle, while its impact on the N cycle was only partial, suggesting potential effect of other additives, such as plasticisers. Overall, our results highlight a significant disruption of microbial processes due to MP pollution, leading to increased greenhouse gas emissions and significant implications on the role of PFW as global C-sinks.

Temporal dynamics of communities on plastic debris in a polluted marine habitat

This study investigated the succession of prokaryotic and eukaryotic communities on polystyrene panels deployed for 25 weeks in a harbour environment influenced by anthropogenic activities. These activities resulted in an excess of nutrients from sewage and agricultural discharges, as well as the release of hydrocarbons and other pollutants. An eDNA metabarcoding approach targeting the 16S and 18S rRNA genes was used. This innovative methodology allowed a detailed analysis of the community development and succession, providing an in-depth view of biodiversity and ecological dynamics associated with plastic substrates. The microbial biofilm community remained stable throughout the experiment enriched in Rhodobacteraceae (16.97 %) and Flavobacteriaceae (17.99 %). Only minor differences observed between the early and late stages, consistent with their identification as key components of the biofilm. For the eukaryotic community, the early colonization stages were dominated by Alveolata (63.39 %) and Stramenopiles (23.53 %). Later stages showed changes in the community with Chlorophyta (20.14 %) and Opisthokonta (94.32 %) being the most abundant phyla. Richness, as alpha diversity index based on retrieved ASVs, varied from 1875 to 2481 and from 159 to 405 for prokaryotes and eukaryotes, respectively. This indicated an adaptive succession of plastic-associated communities in aquatic ecosystems. Potential plastic-degrading groups found in the prokaryotic community showed a dynamic distribution across colonization stages. Trophic dynamics on plastic debris showed that heterotrophs dominated the eukaryotic community. Our results confirmed the role of plastics as vectors in marine ecosystems, for complex communities composed of bacteria, algae, and invertebrates. This highlighted potential risks to the health of marine ecosystems.

Degradation and habitat-dependent colonization of plastics in Caribbean coastal waters and sediments by bacterial communities

This study investigates microbial colonization of plastics in Caribbean coastal waters. We deployed five polymer types, on set with a mild UV-pretreatment and one set without UV-pretreatment, for 4.5 months in the water column and sediment at two locations, and analyzed the epiplastic biofilms with 16S rRNA gene sequencing. While a significant influence of location and habitat was apparent, we could not detect notable effects related to polymer type or UV-pretreatment on microbial community composition. Nevertheless, potential plastic and hydrocarbon degraders constituted up to 43 % of sequences from epiplastic biofilms, suggesting an affinity for plastic. Indeed, utilizing 13C-labeled PE and PP, we determined incorporation of plastic-derived carbon into microbial biomass. We measured isotopically labeled fatty acids in incubations with 13C labeled plastics in both water column and sediments, whether virgin or pre-weathered with UV light. The apparent biodegradation of plastic in benthic habitats challenges the perception of marine sediments as a final sink for polyolefins.

Weathering Process and Characteristics of Microplastics in Coastal Wetlands: A 24-Month In Situ Study

Coastal wetlands function as critical retention zones for environmental microplastics, potentially accelerating their degradation through unique hydrological conditions. This study conducted a comprehensive 24-month in situ experiment at the Chongming Dongtan National Nature Reserve, examining the weathering processes of five morphologically distinct polyethylene (PE), polypropylene (PP), and polystyrene (PS) microplastics. Quarterly analyses revealed progressive surface deterioration in all microplastics after initial exposure, followed by polymer-specific fragmentation patterns and environmental pollutant adherence. Surface elemental analysis showed rising O/C ratios, with intertidal zones exhibiting higher variance (0.0014-0.0096 vs 0.0006-0.0028 supratidal). Carbonyl index (CI) displayed fluctuating increases, with PS showing the highest CI rise (75.75%/year intertidal vs 61.77%/year supratidal). Systematic comparisons identified three weathering determinants: enhanced intertidal degradation from mechanical-photochemical synergy; spherical particles degrading faster than films via larger surface area; and polymer vulnerabilities dictating PS > PP > PE degradation rates. These findings demonstrate that microplastic weathering in coastal wetlands is collectively governed by hydrological conditions, particle morphology, and polymer composition, providing crucial quantitative parameters for assessing environmental persistence and ecological risks in these sensitive transition ecosystems.

Biofilm development as a factor driving the degradation of plasticised marine microplastics

Biodegradation of microplastics facilitated by natural marine biofouling is a promising approach for ocean bioremediation. However, implementation requires a comprehensive understanding of how interactions between the marine microbiome and dominant microplastic debris types (e.g., polymer and additive combinations) can influence biofilm development and drive biodegradation. To investigate this, polystyrene (PS) and polyvinyl chloride (PVC) microplastics (< 200 µm in diameter) were prepared either without any additives (i.e., virgin) or containing 15 wt% of the plasticisers diethylhexyl phthalate (DEHP) or bisphenol A (BPA). Each polymer-plasticiser microplastic combination was exposed to environmentally relevant conditions in a simulated seawater mesocosm representative of tropical reef waters over a 21-day period to allow for natural biofilm development. Following this, microplastic degradation and the colonising bacterial biofilm was assessed as a function of time, polymer and plasticiser type using infrared, thermal, gel permeation and surface characterisation techniques, as well as 16S ribosomal RNA bacterial gene sequencing, respectively. Together, these analyses revealed time-, polymer- and plasticiser-dependent degradation, particularly of the PS-BPA microplastics. Degradation of the PS-BPA microplastics also coincided with changes in bacterial community composition and an increased total relative abundance of putative biodegradative bacteria. These findings indicate that the metabolic potential and biodegradative capability of the colonising marine biofilm can be significantly impacted by the chemical properties of the microplastic substrate, even within short timeframes.

Zooming in the plastisphere: the ecological interface for phytoplankton-plastic interactions in aquatic ecosystems

Phytoplankton is an essential resource in aquatic ecosystems, situated at the base of aquatic food webs. Plastic pollution can impact these organisms, potentially affecting the functioning of aquatic ecosystems. The interaction between plastics and phytoplankton is multifaceted: while microplastics can exert toxic effects on phytoplankton, plastics can also act as a substrate for colonisation. By reviewing the existing literature, this study aims to address pivotal questions concerning the intricate interplay among plastics and phytoplankton/phytobenthos and analyse impacts on fundamental ecosystem processes (e.g. primary production, nutrient cycling). This investigation spans both marine and freshwater ecosystems, examining diverse organisational levels from subcellular processes to entire ecosystems. The diverse chemical composition of plastics, along with their variable properties and role in forming the "plastisphere", underscores the complexity of their influences on aquatic environments. Morphological changes, alterations in metabolic processes, defence and stress responses, including homoaggregation and extracellular polysaccharide biosynthesis, represent adaptive strategies employed by phytoplankton to cope with plastic-induced stress. Plastics also serve as potential habitats for harmful algae and invasive species, thereby influencing biodiversity and environmental conditions. Processes affected by phytoplankton-plastic interaction can have cascading effects throughout the aquatic food web via altered bottom-up and top-down processes. This review emphasises that our understanding of how these multiple interactions compare in impact on natural processes is far from complete, and uncertainty persists regarding whether they drive significant alterations in ecological variables. A lack of comprehensive investigation poses a risk of overlooking fundamental aspects in addressing the environmental challenges associated with widespread plastic pollution.

Temporal succession of marine microbes drives plastisphere community convergence in subtropical coastal waters

Marine plastic pollution is a pervasive environmental issue, with microplastics serving as novel substrates for microbial colonization in aquatic ecosystems. This study investigates the succession of plastisphere communities on four common plastic types (polyethylene, polypropylene, polyethylene terephthalate, and polystyrene) in subtropical coastal waters of Hong Kong SAR. Over a 42-day period, we analysed the temporal development of microbial communities using a three-domain universal metabarcoding method. Our results reveal that temporal succession is a stronger driver of community structure than plastic type, with prokaryotic communities converging across different plastics as biofilms mature. Despite this convergence, plastisphere communities remain distinct from planktonic communities throughout the experiment, suggesting that plastics create unique ecological niches in marine environments. We observed differences in diversity patterns and community composition among prokaryotic, eukaryotic, and chloroplastic communities, highlighting the importance of multi-domain analyses in plastisphere research. Functional predictions suggest potential roles of prokaryotic communities in biogeochemical cycling and possible pathogenicity, highlighting the ecological and public health implications of plastisphere formation. This study provides valuable insights into the dynamics of microbial colonization across domains on marine plastics and enhances our understanding of how these anthropogenic substrates influence microbial ecology in marine ecosystems.

Antibiotic resistance in plastisphere

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

Impacts of wind forcing on microplastics kinematic in a sensitive water area

Microplastics (MPs) have been found in different environmental department globally, and the threat to organisms posed by MPs is also widely recognized. Kinematic characteristics of low-density fiber MPs in Poyang Lake under different due-south wind were calculated by combining hydrodynamic model with particle tracking model in this study. Poyang Lake is divided into north lake and south lake for study based on its topographic and hydrodynamic characteristics, and the results are as follows: the critical wind speeds causing vertical mixing of MPs in the water column ranges from 6 to 9 m·s-1 in the north lake, while it is >9 m·s-1 in the south lake, and the MPs beaching rate decreases by 7.08 %/(m·s-1) as the due-south wind speed increases. The MPs speed is mainly affected by surface current, while the direction of the velocity is more affected by wind. The MPs velocity in the south lake is only 27.10 % of that in the north lake, and the direction is more dispersed, so the due-south wind concentrates the direction of MPs velocity more to the north in the south lake. The northern wards movement of MPs resulted in a noticeable decrease in FS in the south lake, with FS decreasing by 0.10 for every 1 m·s-1 increase in wind speed, and therefore, the due-south wind reduces the ecological risk posed by MPs through reducing the range of movement and retention time. However, since the FS in the north lake has been close to the minimum value of 1, the reduction of the FS is not significant, and the wind reduces the risk mainly by shortening the retention time of the MPs. Therefore, the ecological risk caused by MPs in Poyang Lake under no or weak wind conditions should be taken into consideration.

Biotransformation of microplastics from three-layer face masks by nitrifying-denitrifying consortia

COVID-19 increased microplastics (MP) contamination due to the extensive use of single-use personal protective equipment, particularly three-layer face masks. MP from face masks enter wastewater treatment plants (WWTPs), which were not designed to remove them. We utilized nitrifying-denitrifying microbial consortia and synthetic urban wastewater to evaluate the biotransformation of MP from each layer of three-layer face masks made of polypropylene (PP). The biotransformation carried out by the nitrifying-denitrifying consortia altered the surface of the outer, middle, and inner layers, as a consequence of the chemical modification of the PP-MP structure. Abiotic controls did not show changes on the physicochemical and thermal properties of PP-MP. Biotic tests showed increments in both the carbonyl and hydroxyl indices of the three layers in 42 days. The outer layer showed the greatest degree of biotransformation, which was consistent with morphological changes detected by scanning electron microscopy and in physicochemical properties such as crystallinity, evaporation, and fusion temperature. The nitrifying-denitrifying consortia, which removed 99 % of the total nitrogen from the synthetic urban wastewater, had several genera with proven capacity to biotransform MP such as Cephaloticoccus and Pseudomonas.

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

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

Metatranscriptomics of microbial biofilm succession on HDPE foil: uncovering plastic-degrading potential in soil communities

BACKGROUND

Although plastic pollution is increasing worldwide, very little is known about the microbial processes that take place once plastic debris is incorporated into the soil matrix. In this study, we conducted the first metatranscriptome analysis of polyethylene (PE)-associated biofilm communities in highly polluted landfill soil and compared their gene expression to that of a forest soil community within a 53-day period.

RESULTS

Our findings indicate that the microbial population present in soil contaminated with plastic debris is predisposed to both inhabit and degrade plastic surfaces. Surprisingly, the microbial community from undisturbed forest soil contained a diverse array of plastic-associated genes (PETase, alkB, etc.), indicating the presence of an enzymatic machinery capable of plastic degradation. Plastic-degrading taxa were upregulated in the early stages of biofilm formation. During the maturation of the biofilm, the alkB1/alkM transcripts, which encode PE-degrading enzymes, and transporters such as fadL, livG, livF, livH, and livM were upregulated, along with transcripts associated with the fatty acid β-oxidation pathway.

CONCLUSIONS

In this study, we address the underlying patterns of gene expression during biofilm development in a PE-associated plastisphere in soil and address the pressing question of whether natural microbial communities have the potential to biodegrade petrochemical-based plastic in the soil environment.

Beach wracks microbiome and its putative function in plastic polluted Mediterranean marine ecosystem

The coasts of the world's oceans and seas accumulate various types of floating debris, commonly known as beach wracks, including organic seaweeds, seagrass, and ubiquitous anthropogenic waste, mainly plastic. Beach wrack microbiome (MB), surviving in the form of a biofilm, ensures decomposition and remineralization of wracks, but can also serve as a vector of potential pathogens in the environment. Through the interdisciplinary approach and comprehensive sampling design that includes geological analysis of the sediment, plastic debris composition analysis (ATR-FTIR) and application of 16S rRNA gene metabarcoding of beach wrack MBs, this study aims to describe MB in relation to beach exposure, sediment type and plastic pollution. Major contributors in beach wrack MB were Proteobacteria, Bacteroidetes, Actinobacteria, Planctomycetes, Verrucomicrobia and Firmicutes and there was significant dissimilarity between sample groups with Vibrio, Cobetia and Planococcus shaping the Exposed beach sample group and Cyclobacteriaceae and Flavobacterium shaping the Sheltered beach sample group. Our results suggest plastisphere MB is mostly shaped by beach exposure, type of seagrass, sediment type and probably beach naturalness with heavy influence of seawater MB and shows no significant dissimilarity between MBs from a variety of microplastics (MP). Putative functional analysis of MB detected plastic degradation and potential human pathogen bacteria in both beach wrack and seawater MB. The research provides the next crucial step in beach wrack MP accumulation research, MB composition and functional investigation with focus on beach exposure as an important variable.

Plastic-degrading microbial communities reveal novel microorganisms, pathways, and biocatalysts for polymer degradation and bioplastic production

Plastics derived from fossil fuels are used ubiquitously owing to their exceptional physicochemical characteristics. However, the extensive and short-term use of plastics has caused environmental challenges. The biotechnological plastic conversion can help address the challenges related to plastic pollution, offering sustainable alternatives that can operate using bioeconomic concepts and promote socioeconomic benefits. In this context, using soil from a plastic-contaminated landfill, two consortia were established (ConsPlastic-A and -B) displaying versatility in developing and consuming polyethylene or polyethylene terephthalate as the carbon source of nutrition. The ConsPlastic-A and -B metagenomic sequencing, taxonomic profiling, and the reconstruction of 79 draft bacterial genomes significantly expanded the knowledge of plastic-degrading microorganisms and enzymes, disclosing novel taxonomic groups associated with polymer degradation. The microbial consortium was utilized to obtain a novel Pseudomonas putida strain (BR4), presenting a striking metabolic arsenal for aromatic compound degradation and assimilation, confirmed by genomic analyses. The BR4 displays the inherent capacity to degrade polyethylene terephthalate (PET) and produce polyhydroxybutyrate (PHB) containing hydroxyvalerate (HV) units that contribute to enhanced copolymer properties, such as increased flexibility and resistance to breakage, compared with pure PHB. Therefore, BR4 is a promising strain for developing a bioconsolidated plastic depolymerization and upcycling process. Collectively, our study provides insights that may extend beyond the artificial ecosystems established during our experiments and supports future strategies for effectively decomposing and valorizing plastic waste. Furthermore, the functional genomic analysis described herein serves as a valuable guide for elucidating the genetic potential of microbial communities and microorganisms in plastic deconstruction and upcycling.

Characteristics of microplastics and their abundance impacts on microbial structure and function in agricultural soils of remote areas in west China

As an emergent pollutant, microplastics (MPs) are becoming prevalent in the soil environment. However, the characteristics of MPs and the response of microbial communities to the abundance of MPs in agricultural soils in West China still need to be elucidated in detail. This study utilized the Agilent 8700 Laser Direct Infrared (LDIR) to analyze the characteristics of small-sized MPs (20-1000 μm) in soils from un-mulched and mulched agricultural fields in West China, and illustrated their correlation with microbial diversity. The results revealed a higher abundance of MPs in mulched soil ((4.12 ± 2.13) × 105 items kg-1) than that in un-mulched soil ((1.04 ± 0.26) × 105 items kg-1). The detected MPs were dominated by fragments, 20-50 μm and Polyamide (PA). High-throughput sequencing analysis indicated that alpha diversity (Chao1 and Shannon indices) in the plastisphere was lower compared to that in soil, and varied significantly with MPs abundance in soil. As the abundance of MPs increased, the proportion of soil about the degradation of organic matte and photoautotrophic taxa increased, which showed enrichment in the plastisphere. Functional predictions further indicated that MPs abundance affected potential soil functions, such as metabolic pathways associated with the C and N cycling. The plastisphere showed higher functional abundance associated with organic matter degradation, indicating higher potential health risks compared to soil environments. Based on the RDA analyses, it was determined that environmental physicochemical properties and MPs abundance had a greater impact on fungal communities than on bacterial communities. In general, the abundance of MPs affected the microbial diversity composition and potentially influenced the overall performance of soil ecosystems. This study offers empirical data on the abundance of MPs in long-term mulched agricultural fields and new insights for exploring the ecological risk issues associated with MPs.

Environmental factors control microbial colonization of plastics in the North Sea

Large quantities of plastic enter the oceans each year providing extensive attachment surfaces for marine microbes yet understanding their interactions and colonization of plastic debris remains limited. We investigated microbial colonization of various plastic types (polyethylene, polystyrene, polyethylene-terephthalate, and nylon) in ex-situ incubation experiments. Plastic films, both UV-pretreated and untreated, were exposed to seawater from a coastal and an offshore location in the North Sea. 16S rRNA amplicon sequencing was employed to assess microbial community structures after 5, 10, 30, and 45 days of incubation. Our findings show the significant influence of time, seawater origin and plastic type on microbial community succession. We also identified several genera associated with hydrocarbon or plastic degradation potential as well as genera selecting for specific plastics such as Ketobacter and Microbacterium. Our results highlight potential role of microorganisms in plastic biodegradation and support the idea that microbial colonizers on marine plastics debris seemingly select distinct substrate types.

Omic-driven strategies to unveil microbiome potential for biodegradation of plastics: a review

Plastic waste accumulation has lately been identified as the leading and pervasive environmental concern, harming all living beings, natural habitats, and the global market. Given this issue, developing ecologically friendly solutions, such as biodegradation instead of standard disposal, is critical. To effectively address and develop better strategies, it is critical to understand the inter-relationship between microorganisms and plastic, the role of genes and enzymes involved in this process. However, the complex nature of microbial communities and the diverse mechanisms involved in plastic biodegradation have hindered the development of efficient plastic waste degradation strategies. Omics-driven approaches, encompassing genomics, transcriptomics and proteomics have revolutionized our understanding of microbial ecology and biotechnology. Therefore, this review explores the application of omics technologies in plastic degradation studies and discusses the key findings, challenges, and future prospects of omics-based approaches in identifying novel plastic-degrading microorganisms, enzymes, and metabolic pathways. The integration of omics technologies with advanced molecular technologies such as the recombinant DNA technology and synthetic biology would guide in the optimization of microbial consortia and engineering the microbial systems for enhanced plastic biodegradation under various environmental conditions.

Dynamics and functions of microbial communities in the plastisphere in temperate coastal environments

Microbial attachment and biofilm formation on microplastics (MPs <5 mm in size) in the environment have received growing attention. However, there is limited knowledge of microbial function and their effect on the properties and behavior of MPs in the environment. In this study, microbial communities in the plastisphere were explored to understand microbial ecology as well as their impact on aquatic ecosystems. Using the amplicon sequencing of 16S and internal transcribed spacer (ITS) genes, we uncovered the composition and diversity of bacterial and fungal communities in samples of MPs (fiber, film, foam, and fragment), surface water, bottom sediment, and coastal sand in two contrasting coastal areas of Japan. Differences in microbial diversity and taxonomic composition were detected depending on sample type (MPs, water, sediment, and sand) and the research site. Although relatively higher bacterial and fungal gene counts were determined in MP fragments and foams from the research sites, there were no significant differences in microbial community composition depending on the morphotypes of MPs. Given the colonization by hydrocarbon-degrading communities and the presence of pathogens on MPs, the complex processes of microbial taxa influence the characteristics of MP-associated biofilms, and thus, the properties of MPs. This study highlights the metabolic functions of microbes in MP-associated biofilms, which could be key to uncovering the true impact of plastic debris on the global ecosystem.

Impact of microplastics on microbial community structure in the Qiantang river: A potential source of N2O emissions

This study aimed to investigate the spatial distribution of microplastics (MPs) and the features of the bacterial community in the Qiantang River urban river. Surface water samples from the Qiantang River were analyzed for this purpose. The results of the 16S high-throughput sequencing indicated that the microbial community diversity of MPs was significantly lower than in natural water but higher than in natural substrates. The biofilm of MPs was mainly composed of Enterobacteriaceae (28.00%), Bacillaceae (16.25%), and Phormidiaceae (6.75%). The biodiversity on MPs, natural water, and natural substrates varied significantly and was influenced by seasonal factors. In addition, the presence of MPs hindered the denitrification process in the aquatic environment and intensified N2O emission when the nitrate concentration was higher than normal. In particular, polyethylene terephthalate (PET) exhibited a 12% residue of NO3--N and a 4.2% accumulation of N2O after a duration of 48 h. Further findings on gene abundance and cell viability provided further confirmation that PET had a considerable impact on reducing the expression of nirS (by 0.34-fold) and nosZ (by 0.53-fold), hence impeding the generation of nicotinamide adenine dinucleotide (NADH) (by 0.79-fold). Notably, all MPs demonstrated higher the nirK gene abundances than the nirS gene, which could account for the significant accumulation of N2O. The results suggest that MPs can serve as a novel carrier substrate for microbial communities and as a potential promoter of N2O emission in aquatic environments.

Biofilm-mediated interactions between plastics and radiocesium in coastal environments

A ubiquitous distribution of plastic debris has been reported in aquatic and terrestrial environments; however, the interactions between plastics and radionuclides and the radioactivity of environmental plastics remain largely unknown. Here, we characterize biofilms developing on the surface of plastic debris to explore the role of plastic-associated biofilms as an interaction medium between plastics and radiocesium (137Cs) in the environment. Biofilm samples were extracted from plastics (1-50 mm in size) collected from two contrasting coastal areas in Japan. The radioactivity of plastics was estimated based on the 137Cs activity concentration of the biofilms and compared seasonally with surrounding environmental samples (i.e., sediment and sand). 137Cs traces were detected in biofilms with activity concentrations of 21-1300 Bq·kg-1 biofilm (dry weight), corresponding to 0.04-4.5 Bq·kg-1 plastic (dry weight). Our results reveal the interaction between 137Cs and plastics and provide evidence that organic and mineral components in biofilms are essential in 137Cs retention in environmental plastics. Given the ubiquitous distribution of plastic debris in the environment, more attention should be directed to bioaccumulation and the radioecological impacts of plastic-associated radionuclides on ecosystems.

A closer look at plastic colonisation: Prokaryotic dynamics in established versus newly synthesised marine plastispheres and their planktonic state

The taxonomy of marine plastisphere communities has been extensively studied, demonstrating the ubiquity of hydrocarbonoclastic bacteria of potential biotechnological significance. However, prokaryotic functioning on plastic surfaces has received limited attention, and the question of whether these microorganisms are active and expressing specific molecular mechanisms underpinning plastisphere colonisation remains to be addressed. The aim of this study was to investigate the plastic colonisation process, to identify the active taxa involved in biofilm formation and the mechanisms used to initiate colonisation. To achieve this, a marine plastisphere characterised by active hydrocarbonoclastic genera was used as the inoculum for a short-term microcosm experiment using virgin low-density polyethylene as the sole carbon source. Following incubation for 1 and 2 weeks (representing early and late colonisation, respectively), a taxonomic and comparative metaproteomic approach revealed a significant shift in plastisphere diversity and composition, yet highlighted stability in the predominance of active Proteobacteria spanning 16 genera, including Marinomonas, Pseudomonas, and Pseudoalteromonas. Relative quantification of 1762 proteins shared between the initial plastisphere inoculum, the microcosm plastisphere and the planktonic cells in the surrounding artificial seawater, provided insights into the differential regulation of proteins associated with plastisphere formation. This included the upregulation of proteins mediating cellular attachment in the plastisphere, for example flagellin expressed by Marinomonas, Cobetia, Pseudoalteromonas, and Pseudomonas, and curli expressed by Cobetia. In addition to the differential regulation of energy metabolism in Marinomonas, Psychrobacter, Pseudomonas and Cobetia within the plastisphere relative to the surrounding seawater. Further, we identified the upregulation of amino acid metabolism and transport, including glutamine hydrolysis to glutamate in Marinomonas and unclassified Halomonadaceae, potentially coupled to ammonia availability and oxidative stress experienced within the plastisphere. Our study provides novel insights into the dynamics of plastisphere formation and function, highlighting potential targets for regulating plastisphere growth to enhance plastic bioremediation processes.

Insight into the bacterial community composition of the plastisphere in diverse environments of a coastal salt marsh

The microbial community colonized on microplastics (MPs), known as the 'plastisphere', has attracted extensive concern owing to its environmental implications. Coastal salt marshes, which are crucial ecological assets, are considered sinks for MPs. Despite their strong spatial heterogeneity, there is limited information on plastisphere across diverse environments in coastal salt marshes. Herein, a 1-year field experiment was conducted at three sites in the Yancheng salt marsh in China. This included two sites in the intertidal zone, bare flat (BF) and Spartina alterniflora vegetation area (SA), and one site in the supratidal zone, Phragmites australis vegetation area (PA). Petroleum-based MPs (polyethylene and expanded polystyrene) and bio-based MPs (polylactic acid and polybutylene succinate) were employed. The results revealed significant differences in bacterial community composition between the plastisphere and sediment at all three sites examined, and the species enriched in the plastisphere exhibited location-specific characteristics. Overall, the largest difference was observed at the SA site, whereas the smallest difference was observed at the BF site. Furthermore, the MP polymer types influenced the composition of the bacterial communities in the plastisphere, also exhibiting location-specific characteristics, with the most pronounced impact observed at the PA site and the least at the BF site. The polybutylene succinate plastisphere bacterial communities at the SA and PA sites were quite different from the plastispheres from the other three MP polymer types. Co-occurrence network analyses suggested that the bacterial community network in the BF plastisphere exhibited the highest complexity, whereas the network in the SA plastisphere showed relatively sparse interactions. Null model analyses underscored the predominant role of deterministic processes in shaping the assembly of plastisphere bacterial communities across all three sites, with a more pronounced influence observed in the intertidal zone than in the supratidal zone. This study enriches our understanding of the plastisphere in coastal salt marshes.

Plastic pollution affects ecosystem processes including community structure and functional traits in large rivers

Plastics in aquatic ecosystems rapidly undergo biofouling, giving rise to a new ecosystem on their surface, the 'plastisphere.' Few studies quantify the impact of plastics and their associated community on ecosystem traits from biodiversity and functional traits to metabolic function. It has been suspected that impacts on ecosystems may depend on its state but comparative studies of ecosystem responses are rare in the published literature. We quantified algal biomass, bacterial and algal biodiversity (16S and 18S rRNA), and metabolic traits of the community growing on the surface of different plastic polymers incubated within rivers of the Lower Mekong Basin. The rivers selected have different ecological characteristics but are similar regarding their high degree of plastic pollution. We examined the effects of plastics colonized with biofilms on ecosystem production, community dark respiration, and the epiplastic community's capability to influence nitrogen, phosphorus, organic carbon, and oxygen in water. Finally, we present conceptual models to guide our understanding of plastic pollution within freshwaters. Our findings showed limited microalgal biomass and bacterial dominance, with potential pathogens present. The location significantly influenced community composition, highlighting the role of environmental conditions in shaping community development. When assessing the effects on ecosystem productivity, our experiments showed that biofouled plastics led to a significant drop in oxygen concentration within river water, leading to hypoxic/anoxic conditions with subsequent profound impacts on system metabolism and the capability of influencing biogeochemical cycles. Scaling our findings revealed that plastic pollution may exert a more substantial and ecosystem-altering impact than initially assumed, particularly in areas with poorly managed plastic waste. These results highlighted that the plastisphere functions as a habitat for biologically active organisms which play a pivotal role in essential ecosystem processes. This warrants dedicated attention and investigation, particularly in sensitive ecosystems like the Mekong River, which supports a rich biodiversity and the livelihoods of 65 million people.

Macrogenomes reveal microbial-mediated microplastic degradation pathways in the porcine gut: a hope for solving the environmental challenges of microplastics

It is increasingly recognized that microplastics (MPs) are being transmitted through the food chain system, but little is known about the microorganisms involved in MP degradation, functional biodegradation genes, and metabolic pathways of degradation in the intestinal tract of foodborne animals. In this study, we explored the potential flora mainly involved in MP degradation in the intestinal tracts of Taoyuan, Duroc, and Xiangcun pigs by macrogenomics, screened relevant MP degradation genes, and identified key enzymes and their mechanisms. The pig colon was enriched with abundant MP degradation-related genes, and gut microorganisms were their main hosts. The fiber diet did not significantly affect the abundance of MP degradation-related genes but significantly reduced their diversity. We identified a total of 94 functional genes for MP degradation and classified them into 27 categories by substrate type, with polystyrene (PS), polyethylene terephthalate (PET), and di(2-ethylhexyl) phthalate (DEHP) were the most predominant degradation types. The MP degradation functional genes were widely distributed in a variety of bacteria, mainly in the phylum Firmicutes and Bacteroidetes. Based on the identified functional genes for MP degradation, we proposed a hypothetical degradation mechanism for the three major MP pollutants, namely, PS, PET, and DEHP, which mainly consist of oxidoreductase, hydrolase, transferase, ligase, laccase, and isomerase. The degradation process involves the breakdown of long polymer chains, the oxidation of short-chain oligomers, the conversion of catechols, and the achievement of complete mineralization. Our findings provide insights into the function of MP degradation genes and their host microorganisms in the porcine colon.

Joint effect of black carbon deriving from wheat straw burning and plastic mulch film debris on the soil biochemical properties, bacterial and fungal communities

Black carbon (BC) formed after straw burning remains in farmland soil and coexists with plastic mulch film (PMF) debris. It is unclear how BC influences soil multifunctionality in the presence of PMF debris. In this study, we determined the joint effects of BC and PMF debris on soil biochemical properties and microbial communities. We conducted a soil microcosm experiment by adding BC formed by direct burning of wheat straw and PMF debris (polyethylene (PE) and biodegradable PMF (BP)) into soil at the dosages of 1 %, and soils were sampled on the 15th, 30th, and 100th day of soil incubation for high-throughput sequencing. The results showed that the degradation of PMF debris was accompanied by the release of microplastics (MPs). BC decreased NH4+-N (PE: 68.63 %; BP: 58.97 %) and NO3--N (PE: 12.83 %; BP: 51.37 %) and increased available phosphorus (AP) (PE: 79.12 %; BP: 26.09 %) in soil containing PMF debris. There were significant differences in enzyme activity among all the treatments. High-throughput sequencing indicated that BC reduced bacterial and fungal richness and fungal diversity in PMF debris-exposed soil, whereas PMF debris and BC resulted in significant changes in the proportion of dominant phyla and genera of bacteria and fungi, which were affected by incubation time. Furthermore, BC affected microorganisms by influencing soil properties, and pH and N content were the main influencing factors. In addition, FAPRPTAX analysis indicated that BC and PMF debris affected soil C and N cycling. These findings provide new insights into the response of soil multifunctionality to BC and PMF debris.

Environmental microbial diversity and water pollution characteristics resulted from 150 km coastline in Quanzhou Bay offshore area

As a typical transitional area between the land and sea, the offshore area is subjected to the triple synergistic pressure from the ocean, land, and atmosphere at the same time, and has obvious characteristics such as complex and diverse chemical, physical, and biological processes, coupled and changeable environmental factors, and sensitive and fragile ecological environment. With the deepening of the urbanization process, the offshore area has gradually become the final receptions of pollutants produced by industry, agriculture, and service industries, and plays a key role in the global environmental geochemical cycle of pollutants. In this study, the Quanzhou Bay offshore area was selected as the research object. Sediment and water samples were collected from 8 sampling points within about 150 km of coastline in the Quanzhou Bay offshore area. 16s rDNA high-throughput sequencing method was used to investigate the variation rule of microbial diversity in the offshore area, and multi-parameter water quality analysis was carried out at the same time. The results showed that the distribution characteristics of microbial communities and water quality in the Quanzhou Bay offshore area showed significant differences in different latitudes and longitudes. This difference is closely related to the complexity of offshore area. This study can provide scientific support for protecting and improving the ecological environment of offshore areas.

Biodegradable plastics in Mediterranean coastal environments feature contrasting microbial succession

Plastic pollution of the ocean is a top environmental concern. Biodegradable plastics present a potential "solution" in combating the accumulation of plastic pollution, and their production is currently increasing. While these polymers will contribute to the future plastic marine debris budget, very little is known still about the behavior of biodegradable plastics in different natural environments. In this study, we molecularly profiled entire microbial communities on laboratory confirmed biodegradable polybutylene sebacate-co-terephthalate (PBSeT) and polyhydroxybutyrate (PHB) films, and non-biodegradable conventional low-density polyethylene (LDPE) films that were incubated in situ in three different coastal environments in the Mediterranean Sea. Samples from a pelagic, benthic, and eulittoral habitat were taken at five timepoints during an incubation period of 22 months. We assessed the presence of potential biodegrading bacterial and fungal taxa and contrasted them against previously published in situ disintegration data of these polymers. Scanning electron microscopy imaging complemented our molecular data. Putative plastic degraders occurred in all environments, but there was no obvious "core" of shared plastic-specific microbes. While communities varied between polymers, the habitat predominantly selected for the underlying communities. Observed disintegration patterns did not necessarily match community patterns of putative plastic degraders.

Microplastic-antifouling paint particle contamination alters microbial communities in surrounding marine sediment

Paint used to coat surfaces in aquatic environments often contain biocides to prevent biofouling, and as these coatings degrade, antifouling paint particles (APPs) end up in aquatic, and especially marine, sediments. However, it is currently unclear what further influence APPs in the sediment have on biotic communities or processes. This study investigates how a variety of commercially-available APPs effect the marine microbial community by spiking different laboratory-manufactured APPs to sediment. Following exposure for 30 and 60 days, APPs caused a clear and consistent effect on the bacterial community composition as determined by 16S metabarcoding. This effect was strongest between 0 and 30 days, but continues to a lesser extent between 30 and 60 days. APPs appear to inhibit the highly diverse, but in general rarer, fraction of the community and/or select for specific community members to become more dominant. 71 antifouling-presence and 454 antifouling-absence indicator taxa were identified by indicator analysis. The difference in the level of classification in these two indicator groups was highly significant, with the antifouling-presence indicators having much higher percentage sequence identity to cultured taxa, while the antifouling-absence indicators appear to be made up of undescribed taxa, which may indicate that APPs act as a proxy for general anthropogenic influence or that APP contamination selects for taxa capable of being cultured. Given the clear and consistent effect APPs have on the surrounding sediment microbial community, further research into how APPs affect sediment functional processes and how such effects scale with concentration is recommended to better assess the wider consequences of these pollutants for marine biogeochemical cycles in the future. SYNOPSIS: Microplastic-paint particles are commonly found in marine sediment but little is known about how these, especially antifouling, paint particles affect sediment microbial communities. This study demonstrates that antifouling paint particles fundamentally alter sediment microbial communities.

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

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

Rapid and accurate identification of marine bacteria spores at a single-cell resolution by laser tweezers Raman spectroscopy and deep learning

Marine bacteria have been considered as important participants in revealing various carbon/sulfur/nitrogen cycles of marine ecosystem. Thus, how to accurately identify rare marine bacteria without a culture process is significant and valuable. In this work, we constructed a single-cell Raman spectra dataset from five living bacteria spores and utilized convolutional neural network to rapidly, accurately, nondestructively identify bacteria spores. The optimal CNN architecture can provide a prediction accuracy of five bacteria spore as high as 94.93% ± 1.78%. To evaluate the classification weight of extracted spectra features, we proposed a novel algorithm by occluding fingerprint Raman bands. Based on the relative classification weight arranged from large to small, four Raman bands located at 1518, 1397, 1666, and 1017 cm-1 mostly contribute to producing such high prediction accuracy. It can be foreseen that, LTRS combined with CNN approach have great potential for identifying marine bacteria, which cannot be cultured under normal condition.

Assessing microbial plastic degradation requires robust methods

Plastics are versatile materials that have the potential to propel humanity towards circularity and ultimate societal sustainability. However, the escalating concern surrounding plastic pollution has garnered significant attention, leading to widespread negative perceptions of these materials. Here, we question the role microbes may play in plastic pollution bioremediation by (i) defining polymer biodegradability (i.e., recalcitrant, hydrolysable and biodegradable polymers) and (ii) reviewing best practices for evaluating microbial biodegradation of plastics. We establish recommendations to facilitate the implementation of rigorous methodologies in future studies on plastic biodegradation, aiming to push this field towards the use of isotopic labelling to confirm plastic biodegradation and further determine the molecular mechanisms involved.

Mining strategies for isolating plastic-degrading microorganisms

Plastic waste is a growing global pollutant. Plastic degradation by microorganisms has captured attention as an earth-friendly tactic. Although the mechanisms of plastic degradation by bacteria, fungi, and algae have been explored over the past decade, a large knowledge gap still exists regarding the identification, sorting, and cultivation of efficient plastic degraders, primarily because of their uncultivability. Advances in sequencing techniques and bioinformatics have enabled the identification of microbial degraders and related enzymes and genes involved in plastic biodegradation. In this review, we provide an outline of the situation of plastic degradation and summarize the methods for effective microbial identification using multidisciplinary techniques such as multiomics, meta-analysis, and spectroscopy. This review introduces new strategies for controlling plastic pollution in an environmentally friendly manner. Using this information, highly efficient and colonizing plastic degraders can be mined via targeted sorting and cultivation. In addition, based on the recognized rules and plastic degraders, we can perform an in-depth analysis of the associated degradation mechanism, metabolic features, and interactions.

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.

Accumulation of microplastics in predatory birds near a densely populated urban area

The pollution due to plastic and other anthropogenic particles has steadily increased over the last few decades, presenting a significant threat to the environment and organisms, including avian species. This research aimed to investigate the occurrence of anthropogenic pollutants in the digestive and respiratory systems of four birds of prey: Common Buzzard (Buteo buteo), Black Kite (Milvus migrans), Eurasian Sparrowhawk (Accipiter nisus), and Northern Goshawk (Accipiter gentilis). The results revealed widespread contamination in all species with microplastics (MPs) and cellulosic anthropogenic fibers (AFs), with an average of 7.9 MPs and 9.2 AFs per specimen. Every digestive system contained at least one MP, while 65 % of specimens exhibited MPs in their respiratory systems. This is the work reporting a high incidence of MPs in the respiratory system of birds, clearly indicating inhalation as a pathway for exposure to plastic pollution. The content of MPs and AFs varied significantly when comparing specimens collected from central Madrid with those recovered from other parts of the region, including rural environments, suburban areas, or less populated cities. This result aligns with the assumption that anthropogenic particles disperse from urban centers to surrounding areas. Additionally, the dominant particle shape consisted of small-sized fibers (> 98 %), primarily composed of polyester, polyethylene, acrylic materials, and cellulose fibers exhibiting indicators of industrial treatment. These findings emphasize the necessity for further research on the impact of plastic and other anthropogenic material contamination in avian species, calling for effective strategies to mitigate plastic pollution.

Aeromicrobiology: A global review of the cycling and relationships of bioaerosols with the atmosphere

Airborne microorganisms and biological matter (bioaerosols) play a key role in global biogeochemical cycling, human and crop health trends, and climate patterns. Their presence in the atmosphere is controlled by three main stages: emission, transport, and deposition. Aerial survival rates of bioaerosols are increased through adaptations such as ultra-violet radiation and desiccation resistance or association with particulate matter. Current research into modern concerns such as climate change, global gene transfer, and pathogenicity often neglects to consider atmospheric involvement. This comprehensive review outlines the transpiring of bioaerosols across taxa in the atmosphere, with significant focus on their interactions with environmental elements including abiotic factors (e.g., atmospheric composition, water cycle, and pollution) and events (e.g., dust storms, hurricanes, and wildfires). The aim of this review is to increase understanding and shed light on needed research regarding the interplay between global atmospheric phenomena and the aeromicrobiome. The abundantly documented bacteria and fungi are discussed in context of their cycling and human health impacts. Gaps in knowledge regarding airborne viral community, the challenges and importance of studying their composition, concentrations and survival in the air are addressed, along with understudied plant pathogenic oomycetes, and archaea cycling. Key methodologies in sampling, collection, and processing are described to provide an up-to-date picture of ameliorations in the field. We propose optimization to microbiological methods, commonly used in soil and water analysis, that adjust them to the context of aerobiology, along with other directions towards novel and necessary advancements. This review offers new perspectives into aeromicrobiology and calls for advancements in global-scale bioremediation, insights into ecology, climate change impacts, and pathogenicity transmittance.

Bacterial pathogens associated with the plastisphere of surgical face masks and their dispersion potential in the coastal marine environment

Huge numbers of face masks (FMs) were discharged into the ocean during the coronavirus pandemic. These polymer-based artificial surfaces can support the growth of specific bacterial assemblages, pathogens being of particular concern. However, the potential risks from FM-associated pathogens in the marine environment remain poorly understood. Here, FMs were deployed in coastal seawater for two months. PacBio circular consensus sequencing of the full-length 16S rRNA was used for pathogen identification, providing enhanced taxonomic resolution. Selective enrichment of putative pathogens (e.g., Ralstonia pickettii) was found on FMs, which provided a new niche for these pathogens rarely detected in the surrounding seawater or the stone controls. The total relative abundance of the putative pathogens in FMs was higher than in seawater but lower than in the stone controls. FM exposure during the two months resulted in 3% weight loss and the release of considerable amounts of microfibers. The ecological assembly process of the putative FM-associated pathogens was less impacted by the dispersal limitation, indicating that FM-derived microplastics can serve as vectors of most pathogens for their regional transport. Our results indicate a possible ecological risk of FMs for marine organisms or humans in the coastal and potentially in the open ocean.

Microbes and microplastics: Community shifts along an urban coastal contaminant gradient

Plastic substrates introduced to the environment during the Anthropocene have introduced new pathways for microbial selection and dispersal. Some plastic-colonising microorganisms have adapted phenotypes for plastic degradation (selection), while the spatial transport (dispersal) potential of plastic colonisers remains controlled by polymer-specific density, hydrography and currents. Plastic-degrading enzyme abundances have recently been correlated with concentrations of plastic debris in open ocean environments, making it critical to better understand colonisation of hydrocarbon degraders with plastic degradation potential in urbanised watersheds where plastic pollution often originates. We found that microbial colonisation by reputed hydrocarbon degraders on microplastics (MPs) correlated with a spatial contaminant gradient (New York City/Long Island waterways), polymer types, temporal scales, microbial domains and putative cell activity (DNA vs. RNA). Hydrocarbon-degrading taxa enriched on polyethylene and polyvinyl chloride substrates relative to other polymers and were more commonly recovered in samples proximal to New York City. These differences in MP colonisation could indicate phenotypic adaptation processes resulting from increased exposure to urban plastic runoff as well as differences in carbon bioavailability across polymer types. Shifts in MP community potential across urban coastal contaminant gradients and polymer types improve our understanding of environmental plastic discharge impacts toward biogeochemical cycling across the global ocean.

Microplastics in the insular marine environment of the Southwest Indian Ocean carry a microbiome including antimicrobial resistant (AMR) bacteria: A case study from Reunion Island

The increasing threats to ecosystems and humans from marine plastic pollution require a comprehensive assessment. We present a plastisphere case study from Reunion Island, a remote oceanic island located in the Southwest Indian Ocean, polluted by plastics. We characterized the plastic pollution on the island's coastal waters, described the associated microbiome, explored viable bacterial flora and the presence of antimicrobial resistant (AMR) bacteria. Reunion Island faces plastic pollution with up to 10,000 items/km2 in coastal water. These plastics host microbiomes dominated by Proteobacteria (80 %), including dominant genera such as Psychrobacter, Photobacterium, Pseudoalteromonas and Vibrio. Culturable microbiomes reach 107 CFU/g of microplastics, with dominance of Exiguobacterium and Pseudomonas. Plastics also carry AMR bacteria including β-lactam resistance. Thus, Southwest Indian Ocean islands are facing serious plastic pollution. This pollution requires vigilant monitoring as it harbors a plastisphere including AMR, that threatens pristine ecosystems and potentially human health through the marine food chain.

Novel insight into the aging process of microplastics: An in-situ study in coastal wetlands

Coastal wetlands, the critical interface between the terrestrial and marine environments, provide a dynamic and unique environment for the aging of microplastics (MPs). Nevertheless, both abiotic and biotic processes that contribute to the aging of MPs in coastal wetlands have been largely neglected. In this study, the aging of MPs was continuously characterized in Hangzhou Bay, a representative coastal wetland in Zhejiang, China. Three-month exposure of polymers in sediment-water interface induced the aging phenomenon with embrittlement and exfoliation, as evidenced by simultaneous observed alternations in crystallinity and functional groups. A first-order kinetic model was fitted to describe the rate and degree of aging quantitatively. As evidenced by the carbonyl index, the residence time of all the examined MPs exhibited significant variance, ranging from 335 to 661 days. These variations might be caused by the selective attachment of plastic-degrading microorganisms (such as Moraxella sp. and Rhodococcus sp.). A positive correlation between the carbonyl index, the number of OTUs in the MP-associated biofilm, and irradiation was observed (p < 0.001), suggesting that the aging process may be co-regulated by natural sunlight and wetland microbial colonization. This study sheds new light on the long-term environmental fate of MPs and their associated ecological risks.

Distinct microbial communities degrade cellulose diacetate bioplastics in the coastal ocean

IMPORTANCE

Cellulose diacetate (CDA) is a promising alternative to conventional plastics due to its versatility in manufacturing and low environmental persistence. Previously, our group demonstrated that CDA is susceptible to biodegradation in the ocean on timescales of months. In this study, we report the composition of microorganisms driving CDA degradation in the coastal ocean. We found that the coastal ocean harbors distinct bacterial taxa implicated in CDA degradation and these taxa have not been previously identified in prior CDA degradation studies, indicating an unexplored diversity of CDA-degrading bacteria in the ocean. Moreover, the shape of the plastic article (e.g., a fabric, film, or foam) and plasticizer in the plastic matrix selected for different microbial communities. Our findings pave the way for future studies to identify the specific species and enzymes that drive CDA degradation in the marine environment, ultimately yielding a more predictive understanding of CDA biodegradation across space and time.

Microplastic pollution: Understanding microbial degradation and strategies for pollutant reduction

Microplastics are ubiquitous environmental pollutants with the potential for adverse impacts on ecosystems and human health. These particles originate from the fragmentation of larger plastic items, shedding from synthetic fibers, tire abrasions, and direct release from personal care products and industrial processes. Once released into the environment, microplastics can disrupt ecosystems, accumulate in organisms, cause physical harm, and carry chemical pollutants that pose risks to both wildlife and human health. There is an urgent need to comprehensively explore the multifaceted issue of microplastic pollution and understand microbial degradation to reduce environmental pollution caused by microplastics. This paper presents a comprehensive exploration of microplastics, including their types, composition, advantages, and disadvantages, as well as the journey and evolution of microplastic pollution. The impact of microplastics on the microbiome and microbial communities is elucidated, highlighting the intricate interactions between microplastics and microbial ecosystems. Furthermore, the microbial degradation of microplastics is discussed, including the identification, characterization, and culturing methods of microplastic-degrading microorganisms. Mechanisms of microplastic degradation and the involvement of microbial enzymes are elucidated to shed light on potential biotechnological applications. Strategies for reducing microplastic pollution are presented, encompassing policy recommendations and the importance of enhanced waste management practices. Finally, the paper addresses future challenges and prospects in the field, emphasizing the need for international collaboration, research advancements, and public engagement. Overall, this study underscores the urgent need for concerted efforts to mitigate microplastic pollution and offers valuable insights for researchers, policymakers, and stakeholders involved in environmental preservation.

Disturbance frequency directs microbial community succession in marine biofilms exposed to shear

IMPORTANCE

Disturbances are major drivers of community succession in many microbial systems; however, relatively little is known about marine biofilm community succession, especially under antifouling disturbance. Antifouling technologies exert strong local disturbances on marine biofilms, and resulting biomass losses can be accompanied by shifts in biofilm community composition and succession. We address this gap in knowledge by bridging microbial ecology with antifouling technology development. We show that disturbance by shear can strongly alter marine biofilm community succession, acting as a selective filter influenced by frequency of exposure. Examining marine biofilm succession patterns with and without shear revealed stable associations between key prokaryotic and eukaryotic taxa, highlighting the importance of cross-domain assessment in future marine biofilm research. Describing how compounded top-down and bottom-up disturbances shape the succession of marine biofilms is valuable for understanding the assembly and stability of these complex microbial communities and predicting species invasiveness.

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.

A review on cutinases enzyme in degradation of microplastics

From the surface of the earth to the depths of the ocean, microplastics are a hazard for both aquatic and terrestrial habitats. Due to their small size and vast expanse, they can further integrate into living things. The fate of microplastics in the environment depends upon the biotic components such as microorganisms which have potential enzymes to degrade the microplastics. As a result, scientists are interested in using microorganisms like bacteria, fungi, and others to remediate microplastic. These microorganisms release the cutinase enzyme, which is associated with the enzymatic breakdown of microplastics and plastic films. Yet, numerous varieties of microplastics exist in the environment and their contaminants act as a significant challenge in degrading microplastics. The review discusses the cutinases enzyme degradation strategies and potential answers to deal with existing and newly generated microplastic waste - polyethylene (PE), polyethylene terephthalate (PET), poly-ε-caprolactone (PCL), polyurethanes (PU), and polybutylene succinate (PBS), along with their degradation pathways. The potential of cutinase enzymes from various microorganisms can effectively act to remediate the global problem of microplastic pollution.

Freshwater plastispheres as a vector for foodborne bacteria and viruses

There is growing evidence that plastic particles can accumulate microorganisms that are pathogenic to humans or animals. In the current study, the composition of the plastispheres that accumulated on polypropylene (PP), polyvinyl chloride (PVC), and high-density polyethylene (HDPE) pieces submerged in a river in the southeast Norway was characterized by 16S rRNA amplicon sequencing. Seasonal and geographical effects on the bacterial composition of the plastisphere were identified, in addition to the detection of potential foodborne pathogenic bacteria and viruses as part of the plastisphere. The diversity and taxonomic composition of the plastispheres were influenced by the number of weeks in the river, the season, and the location. The bacterial diversity differed significantly in the plastisphere from June and September, with a generally higher diversity in June. Also, the community composition of the plastisphere was significantly influenced by the geographical location, while the type of plastic had less impact. Plastics submerged in river water assembled a variety of microorganisms including potentially pathogenic bacteria and viruses (noro- and adenovirus) detected by qPCR. Cultivation methods detected viable bacteria such as Escherichia coli and Listeria monocytogenes. The results highlight the need for additional research on the risk of contaminating food with plastic particles colonized with human pathogens through irrigation water.

Role of traveling microplastics as bacterial carriers based on spatial and temporal dynamics of bacterial communities

Microplastics (MPs) are considered as distinct substrates for bacterial colonization, they can carry bacterial communities to travel around environments. The bacterial communities on traveling MPs prefer to be gradually consistent with those on local MPs that were always in the same environment, and this process of change in the bacterial communities on traveling MPs was called 'localization'. However, the dynamics of localization process and their influencing factors are still unclear. Therefore, we simulated the MPs migration process along the water flow direction in the estuary. We used quantitative analysis to study the dynamics of bacterial communities on the migrated MPs. We found the localization characteristics depended on the differences between the former and latter environments, as well as the preexisting bacteria. The localization degree was higher when the former and latter environments were similar. In most cases, compared with the first cultivation of pristine MPs, the time for localization was shorter. Moreover, although the entire bacterial communities tended to be localized, the preexisting bacteria on the migrated MPs had selective effects on subsequent bacterial colonization. Furthermore, the preexisting bacteria on MPs could set up the connections with the bacteria that existed at the latter site, and the stability of the entire bacterial communities on the migrated MPs increased with time. Overall, our findings indicated that the localization characteristics of bacterial communities on traveling MPs were related to the precultured time and environmental differences, which were helpful to understand the colonized bacteria transportation and MPs ecological effects.

Environmental exposure more than plastic composition shapes marine microplastic-associated bacterial communities in Pacific versus Caribbean field incubations

Microplastics have arisen as a global threat to marine ecosystems. In this study, we explored the role that plastic polymer type, incubation time and geographic location have on shaping the microbial community adhered to the microplastics, termed the plastisphere. We performed detailed bacterial plastisphere community analyses on microplastics of six different household plastic polymers, serving as proxies of secondary microplastics, incubated for 6 weeks in coastal Pacific waters. These bacterial communities were compared to the plastisphere communities grown on identical microplastic particles incubated in the coastal Caribbean Sea at Bocas del Toro, Panama. Ribosomal gene sequencing analyses revealed that bacterial community composition did not exhibit a significant preference for plastic type at either site but was instead driven by the incubation time and geographic location. We identified a 'core plastisphere' composed of 57 amplicon sequence variants common to all plastic types, incubation times and locations, with possible synergies between taxa. This study contributes to our understanding of the importance of geography in addition to exposure time, in the composition of the plastisphere.

Extreme weather events as an important factor for the evolution of plastisphere but not for the degradation process

Marine plastics, with their negative effects on marine life and the human health, have been recently recognized as a new niche for the colonization and development of marine biofilms. Members of the colonizing communities could possess the potential for plastic biodegradation. Thus, there is an urgent need to characterize these complex and geographically variable communities and elucidate the functionalities. In this work, we characterize the fungal and bacterial colonizers of 5 types of plastic films (High Density Polyethylene, Low Density Polyethylene, Polypropylene, Polystyrene and Polyethylene Terepthalate) over the course of a 242-day incubation in the south-eastern Mediterranean and relate them to the chemical changes observed on the surface of the samples via ATR-FTIR. The 16s rRNA and ITS2 ribosomal regions of the plastisphere communities were sequenced on four time points (35, 152, 202 and 242 days). The selection of the time points was dictated by the occurrence of a severe storm which removed biological fouling from the surface of the samples and initiated a second colonization period. The bacterial communities, dominated by Proteobacteria and Bacteroidetes, were the most variable and diverse. Fungal communities, characterized mainly by the presence of Ascomycota, were not significantly affected by the storm. Neither bacterial nor fungal community structure were related to the polymer type acting as substrate, while the surface of the plastic samples underwent weathering of oscillating degrees with time. This work examines the long-term development of Mediterranean epiplastic biofilms and is the first to examine how primary colonization influences the microbial community re-attachment and succession as a response to extreme weather events. Finally, it is one of the few studies to examine fungal communities, despite them containing putative plastic degraders.

Improved separation and quantification method for microplastic analysis in sediment: A fine-grained matrix from Arctic Greenland

Microplastic analysis requires effective separation and purification methods, which greatly depend on the matrix and target particle size. Microplastics-sediment extraction usually involves intermediate steps, increasing processing time and particle loss, particularly for particles <100 μm. Here, we propose an improved separation and quantification method for fine-grained sediment that minimizes microplastic loss by reducing intermediate steps. First, the sample is treated with CH3COOH, KOH and NaClO, and only transferred for the density separation (ZnCl2). The extraction efficiency, visually evaluated on spiked samples, was higher than 90% for particles >100 μm and 83% for 63-75 μm particles. This indicates that a sequential extraction method reduces the risk of particle loss, particularly of the small size fraction. Comparatively, the extraction of ABS particles (20-100 μm) was low (30%) but the recovery, assessed via μFTIR, was higher (55%). Additionally, the proposed method can be adapted to other sediment types and environmental matrices.

Microplastics in the environment: A critical overview on its fate, toxicity, implications, management, and bioremediation strategies

Microplastics are small plastic pieces ranging in size from 1μ to <5 mm in diameter, are water-soluble, and can be either primary as they are initially created in small sizes or secondary as they develop due to plastic degradation. Approximately 360 million tons of plastic are produced globally every year, with only 7% recycled, leaving the majority of waste to accumulate in the environment and pose a serious threat in the form of microplastics. All ecosystems, particularly freshwater ecosystems, experience microplastic accumulation and are also prone to degrading processes. Degraded microplastics accumulate in many aquatic systems, contaminate them, and enter the food chain as a result of the excessive discharge of plastic trash annually from the domestic to the industrial sector. Due to their pervasiveness, these tiny plastic particles are constantly present in freshwater environments, which are essential to human life. In this sense, microplastic pollution is seen as a worldwide problem that has a detrimental impact on every component of the freshwater environment. Microplastics act as carriers for various toxic components such as additives and other hazardous substances from industrial and urbanized areas. These microplastic-contaminated effluents are ultimately transferred into water systems and directly ingested by organisms associated with a particular ecosystem. The microplastics components also pose an indirect threat to aquatic ecosystems by adsorbing surrounding water pollutants. This review mainly focuses on the sources of microplastics, the ecotoxicity of microplastics and the impact microplastics have on aquatic and marine life, management, and bioremediation of microplastics. Policies and strategies adopted by the Government to combat microplastic pollution are also discussed in this review.