The structure and assembly mechanisms of plastisphere microbial community in natural marine environment

Marine plastic exposure triggers rapid recruitment of plastic-degrading bacteria and accelerates polymer-specific transformations

Plastic pollution in marine ecosystems is a growing concern, yet the degradation behavior of different plastic types and their interactions with microbial communities remain poorly understood. This study investigated the degradation kinetics and microbial colonization of four widely used plastic materials, surgical masks (most made of PP), PET bottles, PS foam, and PP cups, over 40 days of seawater exposure in the Central Atlantic of Morocco. Mass loss measurement revealed distinct degradation patterns, with PS foam showing the highest mass loss (13 %), followed by PET bottles (5 %), likely due to environmental stressors that promote mechanical fragmentation. Surgical masks and PP cups exhibited minimal degradation, retaining nearly all their original mass, as well as limited extent of biodegradation. Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Diffraction (XRD) analyses showed the formation of oxidative functional groups on PP cups and significant structural changes in PS foam and PET, particularly in their crystalline structures, correlating with their higher mass reduction rates. SEM/EDX biofilm imaging confirmed extensive microbial colonization, particularly on PS and PET surfaces. Using 16S rRNA metabarcoding, we identified a striking enrichment of Exiguobacterium, followed by Pseudomonas, Acinetobacter and Bacillus genera, containing reported plastic degrading strains, which were strongly correlated with the accelerated breakdown of plastics. However, its role in accelerating plastic breakdown in this study remains unclear and may warrant further investigation. Co-occurrence network analysis revealed a progressive shift in microbial community structure, evolving from highly interconnected networks at day 0 to more specialized, modular clusters by day 40, dominated by Proteobacteria and Firmicutes. Atomic Absorption Spectrometry (AAS) demonstrated significant heavy metal accumulation on plastic surfaces, potentially influencing microbial colonization and activity. While the observed fragmentation of PS foam and PET highlights the susceptibility of certain plastics to environmental stressors, this study also positions microbial colonization as a potential contributor to plastic surface changes, providing novel insights into the interplay between microbial communities and plastic degradation in marine environments.

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.

Bacterial pathogen assemblages on microplastic biofilms in coastal waters

Microplastic pollution in coastal ecosystems poses significant environmental risks. Microplastic biofilms were investigated through field incubation in coastal waters over a 21-day period to identify harmful microorganisms. Screening results indicated generally low abundance but highly diverse and variable nature of harmful pathogens on microplastics, largely governed by polymer type in conjunction with water usage. Typhoon shelter exhibited the highest pathogen abundance in both seawater and microplastic biofilms, with the most dominant pathogen species on microplastic biofilms being the atypical Corynebacterium variabile primarily enriched on polystyrene biofilms. Other harmful species, such as Vibrio, Acinetobacter, and Pseudomonas, were found sporadically recruited. Functional annotation and network analysis indicated a co-occurrence of pathogen taxa with keystone taxa like Aeromonas, yet no significant correlation with ARGs. This study showed that the assemblage of pathogens in the plastisphere could be influenced by multiple factors, providing a valuable reference for assessing microplastic-related pathogen risks in coastal waters.

Comprehensive profiling and risk assessment of antibiotic resistomes in surface water and plastisphere by integrated shotgun metagenomics

The ever-increasing microplastics (MPs) and antibiotic-resistance genes (ARGs) in aquatic ecosystems has become a serious global challenging issue. However, the impact of different pollution sources on microbiome and antibiotic resistome in surface water (SW) and plastisphere (PS) remains largely elusive. Here, shotgun metagenomics was used to analyze microbiome structure and antibiotic resistome in SW and PS under the influence of different pollution sources. Pseudomonas were the most abundant genus, followed by Flavobacterium, Acinetobacter, Acidovorax, and Limnohabitans. However, their relative abundance varied significantly both across the sampling sites and habitats i.e. SW and PS (p < 0.05). Additionally, various ARGs were detected in SW and PS, with PS (372) having significantly more potential ARGs than SW (293). The results further showed significant variations in the relative abundance of potential pathogenic bacteria across the sampling sites and habitats (p < 0.05). Further moreover, significant differences were observed in antibiotic resistome risk scores, ARGs and MGEs across different habitats. Over all, this study suggests that pollution source and water quality parameters had a significant impact on microbiome composition and antibiotic resistome in SW and PS.

Unignorable environmental risks: Insight into differential responses between biofilm and plastisphere in sulfur autotrophic denitrification system upon exposure to quaternary ammonium compounds

Concerns of quaternary ammonium compounds (QACs) and microplastics (MPs) as emerging containments accumulating in wastewater treatment plants (WWTPs) have attracted much attention. Plastisphere with distinctive microbial communities might also be the repository for pathogens and resistance genes (RGs). Thus, the effects of three representative QACs with different concentrations on biofilm and plastisphere were studied in sulfur autotrophic denitrification (SAD) system. Over 100 days, 1-5 mg/L QACs exerted few impacts on system stability, whereas 15 mg/L QACs seriously lowered the microbial activity and the inhibitory effects ranked: benzylalkyldimethylethyl ammonium compound > dialkyldimethyl ammonium compound > alkyltrimethyl ammonium compound. Dosing of QACs in SAD system not only altered the microbial community structure and assembly, but also induced higher levels of intracellular RGs and extracellular RGs in plastisphere than in biofilm. Although the free RGs abundances in water slightly lowered, they might also pose great ecological risks. Pathogens identified as the potential hosts of RGs were more prone to colocalizing in plastisphere. Mobile genetic elements directly contributed to the three-fraction RGs transmission in SAD system. This study offered new insights into the differential responses of biofilm and plastisphere under QACs stress and guided for the disinfectants and MPs pollution containment in WWTPs.

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

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

Impacts of aquaculture on nitrogen cycling and microbial community dynamics in coastal tidal flats

The expansion of aquaculture areas has encroached upon vast areas of coastal wetlands and introduced excessive nitrogen inputs, disrupting microbial communities and contributing to various environmental issues. However, investigations on how aquaculture affects microbial communities and nitrogen metabolism mechanisms in coastal tidal flats remain scarce. Hence, we explored the composition, diversity, and assembly processes of nitrogen-cycling (N-cycling) microbial communities in tidal flats in Jiangsu using metagenomic assembly methods. Our study further delved into the seasonal variations of these microbial characteristics to better explore the effects of seasonal changes in aquaculture areas on microbial community. Nitrogen metabolism-related processes and functional genes were identified through the KEGG and NCyc databases. The results revealed significant seasonal variation in the relative abundance and composition of microbial communities. Higher diversity was observed in winter, while the co-occurrence network of microbial communities was more complex in summer. Pseudomonadota emerged as the most abundant phylum in the N-cycling community. Furthermore, pH and NO3-N were identified as the primary factors influencing bacterial community composition, whereas NO2-N was more strongly associated with the N-cycling community. Regarding the nitrogen metabolism processes, nitrogen mineralization and nitrification were predominant in the tidal flat regions. NO2-N and NO3-N exhibited significant effects on several N-cycling functional genes (e.g., nirB, hao, and narG). Finally, neutral and null modeling analyses indicated that bacterial communities were predominantly shaped by stochastic processes, whereas N-cycling communities were largely driven by deterministic processes. These findings highlighted the significant role that aquaculture pollution plays in shaping the N-cycling communities in tidal flats. This underscored the importance of understanding microbial community dynamics and nitrogen metabolism in tidal flats to improve environmental management in coastal aquaculture areas.

Untargeted metabolomic insights into plastisphere communities in European rivers

Every year, rivers introduce a staggering amount of hundred kilotons of plastic into the Oceans. This plastic is inhabited by microorganisms known as the plastisphere, which can be transferred between different ecosystems through the transport of microplastics. Here, we simulated the microbial colonization of polyethylene-based plastic pellets that are classically used to manufacture large-scale plastic products. The pellets were immersed for 1 month in four to five sampling stations along the river-to-sea continuum of nine of the major European rivers. This study presents the first untargeted metabolomics analysis of the plastisphere, by using ultra high-performance liquid chromatography coupled to high-resolution mass spectrometry (UHPLC-HRMS). The plastisphere metabolomes were similar in the Rhine and Rhone rivers, while being different from the Tiber and Loire rivers, which showed greater similarity to the Thames and Seine rivers. Interestingly, we found a clear distinction between plastisphere metabolomes from freshwater and marine water in most of the river-to-sea continuum, thus suggesting a complete segregation in plastisphere metabolites that is not consistent with a major transfer of microorganisms between the two contrasted ecosystems. Putative annotations of 189 discriminating metabolites suggested that lipid metabolism was significantly modulated. These results enlightened the relevance of using environmental metabolomic as complementary analysis to the current OMICs analysis.

Salinity as a key factor affects viral structure, function, and life strategies in lakes from arid and semi-arid regions

Salinity impacts lake microorganisms in arid and semiarid zones, affecting climate change. Viruses regulate community structure, facilitate gene transfer, and mediate nutrient cycling. However, studies on the diversity and functional differences of viruses in lakes of varying salinity are limited. Thus, we investigated metagenomic data from 20 lakes in Xinjiang Province, China, to determine viral distribution, virus-host linkage, function, and drivers in lakes of varying salinity. The results showed that salinity shaped the distribution of viral community composition, and Hafunaviridae was the dominant virus in high-salinity lakes. All the metagenome-assembled genomes (MAGs) belonging to Halobacteriota were predicted as hosts, with a lysogenic lifestyle predominating the life strategy, implying their potential protection in salt lakes. Moreover, some auxiliary metabolic genes (AMGs), such as cpeT and PTOX, were related to antioxidant and stress responses, which might help the host survive high salinity stress-induced peroxidation. Notably, the main antibiotic resistance genes (ARGs) carried by viruses, which conferred resistance to polymyxin and trimethoprim, related to the local use of veterinary antibiotics, suggesting that they are potential vehicles for the transmission of ARGs. Overall, these findings suggest that lake systems include unique viral varieties that may influence microbial ecosystems and host metabolism related to environmental adaptability.

Colonization time of plastisphere drives the dynamics of organic carbon stability and microbial communities in seagrass bed sediments

Microplastic (MP) pollution in seagrass bed ecosystems has emerged as a significant global concern. However, the effects of plastisphere formation on organic carbon pools and microbial communities in these ecosystems remain unknown. We conducted a 56-day microcosm incubation experiment to study the dynamic changes in physicochemical characteristics, organic carbon fractions and stability, and bacterial community structure in seagrass bed sediments during the plastisphere formation process for polystyrene (PS) and polylactic acid (PLA). The results revealed significant weathering and biofilm formation on both PS and PLA. MPs altered the microbial community structure in seagrass bed sediments, leading to species turnover. Colonization time emerged as the key factor driving microbial community assembly, with ecological processes shifting from dispersal limitation to ecological drift in the plastisphere, while sediments maintained dispersal limitation as the dominant process. The formation of the plastisphere significantly influenced seagrass bed sediment microbial carbon (MBC) and organic carbon pool stability. MPs weathering negatively correlated with sediment properties but positively correlated with microbial communities, jointly modulating carbon pool stability. This study provided a new insight into the potential risks posed by MPs to carbon cycling and the ecological functioning of seagrass bed ecosystems.

New insights into odor release from sediments in Lake Chaohu and the potential role of sediment microbial communities

Odor events often occur along with algal blooms, posing potential threats to water quality and human health. However, studies on the role of sediments and microbial communities in the production and release of odor compounds remain limited. Seasonal monitoring of Lake Chaohu revealed that pore-terpenoids significantly contributed to terpenoid concentrations in water, explaining 37.1 % of their variability. Environmental factors like temperature primarily influenced terpenoid concentrations by regulating the diffusion of pore-terpenoids. Conversely, pore-nor-carotenoids explained only 11.2 % of nor-carotenoid variability, with phytoplankton communities explaining 59.4 %. Abiotic factors like nutrients influenced nor-carotenoid levels by impacting phytoplankton growth. Microbial communities with a greater proportion of cyanobacteria exhibited more fragile microbial networks, increased competition, and enhanced metabolic activity. We hypothesized that microbial community composition may influence odor production. Laboratory experiments further supported this: sediments with added cyanobacteria showed a 48.1 % reduction in 2-methylisoborneol contents after 30-day incubation, whereas the control group exhibited a 66.38 % increase. Conversely, the experimental group showed significant increases in β-cyclocitral (99.19 %) and β-ionone (48.55 %), while the control group experienced reductions of 54.01 % and 43.53 %, respectively. These findings underscore the importance of considering microbial interactions and sediment dynamics in future odor research, offering insights for water quality management in eutrophic lakes.

Potential ecological risk of microplastics contamination to environment in protect area lakes

Microplastics (MPs) in freshwater have been extensively studied on a global scale. However, a deeper understanding is still required regarding the occurrence characteristics and ecological risks of MPs in protected area lakes(PAL). Here, the study investigated MPs pollution in PAL, outside protected areas lakes (OPAL), and ponds (OPAP) in the eastern Qinghai-Tibetan Plateau, and a comprehensive analysis was conducted comparing lakes or ponds from different income regions. The results showed that PAL has a single source of contamination, while OPAL and OPAP exhibited more diverse MP sources. The surface of all samples showed significant physicochemical changes like oxygen-containing functional groups and potential signs of biodegradation. Microbiome analysis identified potential plastic-degrading bacteria on MPs, which varied by polymer type. Ecological risk assessment revealed that OPAL and OPAP face higher ecological risks, particularly from polymers like PVC and PC, while PAL has low risk. However, we should also consider the environmental changes over the past 100 years of history in this region and emphasize the environmental health of PAL. Notably, MPs pollution is more severe in lower-middle-income regions, highlighting the urgent need for stricter controls.

Microbiomes of coastal sediments and plastispheres shaped by microplastics and decabrominated diphenyl ether

Deciphering the impact of microplastic and persistent organic pollutants (POPs) co-contamination on coastal sediment is critical for developing effective remediation strategies for polluted sites yet remains underexplored. This study investigated the interactions between microplastics, decabrominated diphenyl ether (deca-BDE), and their co-contamination effects on the evolvement of coastal sediment and plastisphere microbiomes for over 2 years. Results showed that deca-BDE was naturally debrominated in sediments via diverse pathways, with microplastic polystyrene stimulating the debromination rate by up to 78.7 ± 10.0 %. The putative OHRB Dehalobacter and uncultured Dehalococcoidia populations were identified responsible for the complete debromination. Co-exposure to microplastics and deca-BDE induced significant shifts in community composition, diversity, and function in the sediment microbiomes, while plastisphere microbiomes exhibited distinct compositions and functional profiles, specializing in pathogenicity, pollutant degradation, and biogeochemical cycling. The type of plastics and the presence of deca-BDE influenced the plastisphere composition. Changes in sediment properties and debromination activity profoundly shaped microbial communities, with deterministic assembly dominating the plastisphere. Co-contamination increased the complexity, modularity, and stability of the plastisphere networks, creating unique niches for OHRB. These findings highlight the intricate interplay between microplastics, deca-BDE, and microbiomes, with significant implications for ecosystem health and remediation efforts.

Antibiotic resistance genes and virulence factors in the plastisphere in wastewater treatment plant effluent: Health risk quantification and driving mechanism interpretation

Microplastics (MPs) are ubiquitous in wastewater treatment plants (WWTPs) and provide a unique niche for the spread of pollutants. To date, risk assessments and driving mechanisms of pathogens, antibiotic resistance genes (ARGs), and virulence factors (VFs) in the plastisphere are still lacking. Here, the microbiota, ARGs, VFs, their potential health risks, and biologically driving mechanisms on polythene (PE), polyethylene terephthalate (PET), poly (butyleneadipate-co-terephthalate) and polylactic acid blends (PBAT/PLA), PLA MPs, and gravel in WWTP effluent were investigated. The results showed that plastisphere and gravel biofilm harbored more distinctive microorganisms, promoting the uniqueness of pathogens, ARGs, and VFs compared to WWTP effluent. The abundance of major pathogens, ARGs, and VFs in the plastisphere was 1.01-1.35 times higher than that in the effluent. The high health risk of ARGs (HRA) calculated by fully considering the abundance, clinical relevance, pathogenicity, accessibility and mobility, and the high proportion of resistance contigs with mobile genetic elements confirmed that the plastisphere posed the highest potential health risk. Candidatus Microthrix and Candidatus Promineifilum were the essential hosts of ARGs and VFs in the plastisphere and gravel biofilm, respectively. High metabolic activity such as amino acid metabolism and biosynthesis of secondary metabolites, and highly expressed key genes increased the synthesis of ARGs and VFs. The primary mechanisms driving ARG enrichment in the plastisphere were enhanced microbial metabolic activity, increased frequency of horizontal gene transfer, heightened antibiotic inactivation and efflux, and reduced cell permeability. This study provided new insights into the ARGs, VFs, and health risks of the plastisphere and emphasized the importance of strict control of wastewater discharge.

Impact of microplastics on microbial diversity and pathogen distribution in aquaculture ecosystems: A seasonal analysis

Microplastics, as a prominent emerging pollutant in marine environments, pose a serious threat to the stability of marine ecosystems due to their resistance to biodegradation. MPs act as substrates for biofouling and potentially promote the spread of harmful microorganisms. Research indicates that human activities exacerbate MPs pollution in aquaculture environments, significantly increasing their abundance. This study focused on the aquaculture environment of the large yellow croaker (Larimichthys crocea), one of the most extensively farmed fish species in coastal regions. We conducted a comprehensive analysis of microbial diversity on the biofilms covering MPs and in the surrounding aquaculture water, with a focus on the distribution of pathogens on MPs. Furthermore, this study investigated the impact of seasonal variations on the microbial communities within these biofilms. Sequencing analysis revealed that the α-diversity of microbial communities on MPs was lower than that in aquaculture water during winter but higher in summer, indicating a seasonal shift in microbial community structure. PICRUSt predictions suggested that microbes on MPs possess unique metabolic pathways. Co-occurrence network analysis demonstrated that during summer, the microbial communities on MPs revealed increased connectivity and functional modularity, whereas microbial communities in aquaculture water showed stronger interactions in winter. Additionally, several potential pathogens, including Vibrio and Pseudomonas, were detected in the MPs biofilms. These findings underscore the ways in which MPs influence the microbial community structure in aquaculture environments, increasing health risks to the ecosystem. This research offers significant insights into the ecological impacts of MPs pollution on microbial communities in aquaculture ecosystems.

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.

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

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

Accelerated stochastic processes of plankton community assembly due to tidal restriction by seawall construction in the Yangtze River Estuary

Seawall construction has complex ecological impacts. However, the ecological mechanisms within plankton communities under tidal restriction resulting from seawall construction remain unexplored. Using environmental DNA (eDNA) metabarcoding, this study examined the impact of seawall construction on the assembly process of planktonic eukaryote and bacteria communities from the unrestricted area and the tide-restricted area in the Chongming Dongtan Nature Reserve of Yangtze River Estuary. While environmental heterogeneity did not exert a significant influence on alpha diversity of plankton, it had a significant impact on community structure. Variation partitioning analysis (VPA) and neutral community model indicated that neither environmental nor spatial factors were predominant drivers of plankton community composition and structure, instead, they were influenced by stochastic processes. Moreover, it was observed that the relative significance of stochastic processes in the tide-restricted area exceeded that in the unrestricted area. High habitat uniformity and water connectivity resulting from seawall construction may facilitate homogenization and spread among high-abundance groups. The results have significant implications for understanding the mechanisms underlying succession and composition, and for improving ecological assessment and remediation efforts in areas impacted by tidal restriction.

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

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

Structure and assembly mechanisms of the microbial community on an artificial reef surface, Fangchenggang, China

The construction of artificial reefs (ARs) is an effective way to restore habitats and increase and breed fishery resources in marine ranches. However, studies on the impacts of ARs on the structure, function, and assembly patterns of the bacterial community (BC), which is important in biogeochemical cycles, are lacking. The compositions, diversities, assembly patterns, predicted functions, and key environmental factors of the attached and free-living microbial communities in five-year ARs (O-ARs) and one-year ARs (N-ARs) in Fangchenggang, China, were analyzed via 16S rRNA gene sequencing. Proteobacteria was the dominant taxon in all the samples, with an average relative abundance of 44.48%, followed by Bacteroidetes (17.42%) and Cyanobacteria (15.19%). The composition of bacterial phyla was similar between O-ARs and N-ARs, but the relative abundance of Cyanobacteria was greater in the water column (38.56%) than on the AR surface (mean of 7.40%). The results revealed that the Shannon‒Wiener diversity indices were 5.64 and 5.45 for O-ARs and N-ARs, respectively. Principal coordinate analysis (PCoA) revealed different distributions of O-ARs and N-ARs in the microbial community. Additionally, network analysis revealed that the bacterial community was more complex and stable in O-ARs than in N-ARs, indicating that the 5-year AR presented a more diverse and stable microbial community overall. The KEGG database was used to predict that nitrogen metabolism, carbon metabolism, and membrane transport were the dominant microbial functions, accounting for 29.93% of the total functional abundances. The results of the neutral community model revealed that stochastic processes (67.2%) dominated the assembly of BCs. Interestingly, deterministic processes may be increasingly important in community aggregation over time. Moreover, a null model revealed that dispersal limitation was the most important process among the stochastic processes, accounting for 57.14% of the total. In addition, redundancy analysis (RDA) revealed that hydrological factors obviously impacted the structure and function of the microbial community. Our results showed that the construction of ARs slightly promotes local diversities in the structure and function of the microbial community, indicating it requires a longer time to enhance the diversity of the microbial community on artificial reefs. KEY POINTS: • Artificial reefs facilitate the diversity and functions of the microbial community • Stochastic processes dominate the assembly of the microbial community in artificial reefs • Nitrogen and carbon metabolism dominate microbial functions in artificial reefs.

Effects of Different Types of Microplastics on Cold Seep Microbial Diversity and Function

The massive production and widespread use of plastics have resulted in a growing marine plastic pollution problem. Cold seep ecosystems are maintained by microorganisms related to nitrogen and carbon cycling that occur in deep-sea areas, where cold hydrocarbon-rich water seeps from the ocean floor. Little is known about plastic pollution in this ecosystem. To fill this knowledge gap, we collected sediment and seawater samples from the Haima cold seep and conducted laboratory cultivation experiments, simulating in situ environmental conditions. Environmental factors and microbial genetics were analyzed at different stages over a 2-month cultivation period. Our main conclusions are as follows: (1) When microplastics (MPs) were added to sediment and seawater environments, the microbial communities most closely resembled those of the original habitat. The changes in the plastisphere communities were mainly associated with the culture time. (2) The co-occurrence network of the plastisphere was more fragile than that of environments. (3) Multiple environmental factors determined the community composition, whereas a small number of environmental variables drove the community function. MPs affected nitrogen cycling and methane metabolism and might aggregate pathogenic species. This work provides a better perspective of the effect of MPs on the community structure and function in cold seeps.

Seasonal Dynamics of the Bacterial Community in Lake Urmia, a Hypersaline Ecosystem

Lake Urmia is one of the world's most unique and hypersaline aquatic ecosystems. The aim of this study was to investigate the diversity, abundance and frequency of these microorganisms in water samples from the eastern regions of the lake over four seasons. Amplicon sequencing for the 16S rRNA gene was performed to examine bacterial communities in the samples. The study revealed significant seasonal variations in water quality parameters and their influence on the microbial communities. Majority and rarity analyses showed that winter and spring had higher core abundance and higher Gini index values, indicating a greater dominance of certain genera, while autumn and summer had a more balanced distribution. Analysis of beta diversity using the Bray-Curtis dissimilarity index emphasized that bacterial communities diverge most strongly in summer and winter, reflecting the significant changes in the environment with the season. Overall, understanding the seasonal variation in water chemistry and bacterial communities is critical for effective ecosystem management and conservation efforts.

A baroduric immobilized composite material promoting remediation of oil-polluted sediment at typical deep-sea condition: The performances and potential mechanisms

Contriving immobilized bioreagent is of great significance to enhance bioremediation of marine oil pollution. However, there remains a notable scarcity of correlational study conducted at deep sea condition. Herein, we first developed a baroduric microsphere encasing biotic and chemical materials to remediate oil-contaminated sediments at deep-sea microcosm. Total oil degradation efficiency of microsphere-treated group reached 71% within a month, representing an approximate 35% increase compared to natural remediation. Absorption and biodegradation by microsphere provided a comparable contribution to oil elimination. Together with scanning electron microscope observation, the physical mechanism was that the reticulate structure of microsphere surface facilitating oil adsorption and bacteria attachment. Via metabarcoding analysis for meta and metabolically-active microbes, we demonstrated the primary working center was located at the microsphere. Proteobacteria, Firmicutes, Bacteroidota and Desulfobacterota were the key activated bacteria. More importantly, we revealed the ecological mechanisms were associated with the following aspects: 1) the addition of microsphere significantly improved the metabolic activity of bacteria (particularly including several oil-degrading taxa); 2) the microspheres enhanced ecological stability and microbial functional diversification during bioremediation; 3) expressing activity of pathways involving oil component degradation, biosurfactant production, biofilm architecture, biogeochemical and energy cycling all were observed to be up-regulated in microsphere-treated samples. Altogether, our results provide important theoretical guidance and data support on application of immobilization technology in removing in-situ oil pollution of deep-sea sediment.

Comparative analysis of the microbial plastisphere at three sites along the Sarno river (Italy)

This study investigated microplastics (MP) and their associated microbial plastisphere in the Sarno river (Italy), its estuary and in the nearby coastal area in January 2020. Scanning Electron Microscopy (SEM), High Throughput Sequencing (HTS) and Fourier-Transformed Infrared Spectroscopy (FTIR) were used to characterize the collected MPs and their associated microbes. The three stations sampled differed substantially for MP concentrations and microbial communities, with the estuarine station showing very high MP concentrations (2048.6 MP m-3), highlighting the threat represented by the river for the coastal marine area and its ecosystem. The prokaryotic plastisphere showed differences between the three stations sampled, in terms of community composition, with only 75 Amplicon Sequence Variants (ASV) in common. The Comamonadaceae was the most abundant family in MP-attached and freshwater communities, and this lifestyle seems to be pivotal in the colonization of new habitats while flowing towards the sea. The results highlight the importance of the plastisphere in colonization of new habitats and support the need of correct management and risk mitigation efforts.

Distinctive patterns of bacterial community succession in the riverine micro-plastisphere in view of biofilm development and ecological niches

Exploring plastic bacterial community succession is a crucial step in analyzing and predicting the ecological assembly processes of the plastisphere and its associated environmental impacts. However, microbial biofilm development and niche differentiation during plastic bacterial community succession have rarely scarcely considered. Here, we assessed the differences between three microplastics (MPs) and two natural polymers in terms of biofilm development and niche properties during bacterial community succession, and identified a genus of MPs-degrading bacteria with strong competitive potential in the plastisphere. MPs biofilm development exhibits secondary succession characteristics, whereas natural polymer biofilms persist during the primary succession stage. During succession in plastic bacterial communities, the relationship between nutrient resources and microbial competition was reflected in a positive correlation between species competition and niche breadth, which contradicted the common belief that increased nutrient availability leads to reduced competition. Furthermore, the co-occurrence network revealed that specialists were species with greater competitive potential within the plastisphere. Additionally, the MPs-degrading Exiguobacterium genus represented a key taxon in the plastisphere. Our study provides a reliable pathway for revealing the specificity of plastic bacterial community succession from multiple perspectives and enhances the understanding of ecological assembly processes in the plastisphere.

Pretreated polystyrene is degraded by a microbial consortium enriched from wetland plastic waste

The biodegradation of polystyrene (PS), a type of plastic with aromatic rings in its polymer chain, is a critical environmental goal worldwide. Microbial degradation of PS has been reported, but the underlying mechanisms are poorly understood. Here, we constructed a microcosm wetland containing PS plastic. We isolated six highly efficient PS plastic-degrading bacterial strains and created a microbial consortium (MCs) consisting of these strains. After a 30-day incubation period, MCs-treated PS exhibited hallmarks of degradation, including -CO- formation, reduced hydrophobicity, surface porosity, and 20 % weight loss. The efficiency of PS degradation was enhanced by using a combination of physical-chemical pretreatment and biological methods, increasing the microbial degradation rate by 20 %. Antioxidant 2246 (C23H32O2) was detected in the culture supernatant via GC-MS. Metatranscriptomic sequencing analysis provided insight into the possible metabolic pathway of PS degradation by the composite bacteria. We identified 31 highly expressed genes encoding proteins that function in carbon metabolism pathways and 34 unique proteases which catalyze the cleavage of long polymer chains. The resulting small molecules are absorbed and further degraded intracellularly by enzymes such as coenzyme synthase, hydratase, transferase, carboxylase, and dehydrogenase. These findings lay the foundation for the efficient and sustainable degradation of PS.

Response of sedimentary microbial community and antibiotic resistance genes to aged Micro(Nano)plastics exposure under high hydrostatic pressure

Several studies reported that the presence of microplastics (MPs)/nanoplastics (NPs) in marine environments can alter microbial community and function. Yet, the impact of aged MPs/NPs on deep sea sedimentary ecosystems under high hydrostatic pressure remains insufficiently explored. Herein, the sedimentary microbial community composition, co-occurrence network, assembly, and transfer of antibiotic resistance genes (ARGs) in response to aged MPs/NPs were investigated. Compared with the control, NPs addition significantly reduced bacterial alpha diversity (p < 0.05), whereas MPs showed no significant impact (p > 0.05). Moreover, networks under NPs exhibited decreased complexity than that under MPs and the control, including edges, average degree, and the number of keystone. The assembly of the microbial community was primarily governed by stochastic processes, and aged MPs/NPs increased the importance of stochastic processes. Moreover, exposure to MPs/NPs for one month decreased the abundance of antibiotic resistance genes (ARGs) (from 94.8 to 36.2 TPM), while exposure for four months increased the abundance (from 40.6 to 88.1 TPM), and the shift of ARGs in sediment was driven by both functional modules and microbial community. This study is crucial for understanding the stress imposed by aged MPs/NPs on sedimentary ecosystems under high hydrostatic pressure.

Mechanisms underpinning microplastic effects on the natural climate solutions of wetland ecosystems

Wetland ecosystems are vital carbon dioxide (CO2) sinks, offering significant nature-based solutions for global climate mitigation. However, the recent influx of microplastic (MP) into wetlands substantially impacts key drivers (e.g., plants and microorganisms) underpinning these wetland functions. While MP-induced greenhouse gas (GHG) emissions and effects on soil organic carbon (SOC) mineralization potentially threaten the long-term wetland C-climate feedbacks, the exact mechanisms and linkage are unclear. This review provides a conceptual framework to elaborate on the interplay between MPs, wetland ecosystems, and the atmospheric milieu. We also summarize published studies that validate possible MP impacts on natural climate solutions of wetlands, as well as provide extensive elaboration on underlying mechanisms. We briefly highlight the relationships between MP influx, wetland degradation, and climate change and conclude by identifying key gaps for future research priorities. Globally, plastic production, MP entry into aquatic systems, and wetland degradation-related emissions are predicted to increase. This means that MP-related emissions and wetland-climate feedback should be addressed in the context of the UN Paris Climate Agreement on net-zero emissions by 2050. This overview serves as a wake-up call on the alarming impacts of MPs on wetland ecosystems and urges a global reconsideration of nature-based solutions in the context of climate mitigation.

Interpretation of bacterial composition patterns and community assembly processes in the rhizosphere soil of tea trees in karst areas

RESEARCH BACKGROUND AND PURPOSE

Soil microorganisms that are closely related to plants are important factors affecting plant health. Therefore, elucidating the abundant and rare bacterial species in soil associated with plant diseases is crucial for understanding ecological processes, maintaining the stability of microecological environments, and formulating microbial strategies that are consistent with modern agricultural development.

RESULTS

Tea leaf blight leads to an increase in bacterial diversity in the rhizosphere. Random processes dominate the assembly of abundant and rare taxa, while abundant taxa are also influenced by deterministic processes. In the co-occurrence network, the increase in bacterial community diversity mediated by tea cloud leaf blight enhances the stability of the network. Meanwhile, the proportion of positive correlation between rare taxa is relatively high, and the relationship between rare taxa and intermediate taxa is closer. This highly diverse bacteria community maintained the structure and stability of the community to a certain extent.

CONCLUSION

The rare taxa in the rhizosphere and the rhizosphere bacterial community mediated by tea leaf blight have high diversity, which is of great significance for maintaining the stability of the rhizosphere bacterial ecological network. In the future, we will further explore the dynamic changes and interaction patterns of the species in the rhizosphere soil affected by tea tree diseases, and their ecological functions and importance in areas of habitat fragmentation. Overall, there are many microbial resources in the rhizosphere microbiota under the influence of plant diseases that can be used for agricultural practice. The results of this study will enrich the insights into ecodynamics of bacteria in karst areas, especially in karst tea gardens.

High-altitude aquatic ecosystems offer faster aging rate of plastics

While research on the aging behavior of plastics in aquatic systems is extensive, studies focusing on high-altitude ecosystems, characterized by higher solar radiation and lower temperatures, remain limited. This study investigated the long-term aging behavior of non-biodegradable plastics (non-BPs), namely polyethylene terephthalate (PET) and polypropylene (PP) and biodegradable plastics (BPs), specifically polylactic acid plus polybutylene adipate-co-terephthalate (PLA + PBAT) and starch-based plastic (SBP), in a tributary of the Yarlung Zangbo River on the high-altitude Tibetan Plateau. Over 84 days of field aging, all four types of plastics exhibited initial rapid aging followed by deceleration. This aging process can be divided into two phases: rapid surface oxidation aging and an aging plateau phase. Notably, PP aged at a rate comparable to BPs, contrary to expectations of faster aging for BPs. Compared to low-altitude aquatic ecosystems, plastics in this study showed a faster aging rate. This was primarily due to intense ultraviolet radiation causing severe photoaging. Furthermore, the lower temperatures contributed to the formation of thinner biofilms. These thinner biofilms exhibited a reduced capacity to block light, further exacerbating the photoaging process of plastics. Statistical analysis results indicated that temperature, total nitrogen TN, and total phosphorus TP were likely the main water quality parameters influencing plastic aging. The varying effects of water properties and nutrients underscore the complex interaction of water quality parameters in high-altitude environments. Given the delicate nature of the high-altitude environment, the environmental impact of plastics, especially BPs, warrants careful consideration.

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.

Taxonomic variation, plastic degradation, and antibiotic resistance traits of plastisphere communities in the maturation pond of a wastewater treatment plant

Wastewater treatment facilities can filter out some plastics before they reach the open environment, yet microplastics often persist throughout these systems. As they age, microplastics in wastewater may both leach and sorb pollutants and fragment to provide an increased surface area for bacterial attachment and conjugation, possibly impacting antimicrobial resistance (AMR) traits. Despite this, little is known about the effects of persistent plastic pollution on microbial functioning. To address this knowledge gap, we deployed five different artificially weathered plastic types and a glass control into the final maturation pond of a municipal wastewater treatment plant in Ōtautahi-Christchurch, Aotearoa/New Zealand. We sampled the plastic-associated biofilms (plastisphere) at 2, 6, 26, and 52 weeks, along with the ambient pond water, at three different depths (20, 40, and 60 cm from the pond water surface). We investigated the changes in plastisphere microbial diversity and functional potential through metagenomic sequencing. Bacterial 16S ribosomal RNA genes composition did not vary among plastic types and glass controls (P = 0.997) but varied among sampling times [permutational multivariate analysis of variance (PERMANOVA), P = 0.001] and depths (PERMANOVA, P = 0.011). Overall, there was no polymer-substrate specificity evident in the total composition of genes (PERMANOVA, P = 0.67), but sampling time (PERMANOVA, P = 0.002) and depth were significant factors (PERMANOVA, P = 0.001). The plastisphere housed diverse AMR gene families, potentially influenced by biofilm-meditated conjugation. The plastisphere also harbored an increased abundance of genes associated with the biodegradation of nylon, or nylon-associated substances, including nylon oligomer-degrading enzymes and hydrolases.IMPORTANCEPlastic pollution is pervasive and ubiquitous. Occurrences of plastics causing entanglement or ingestion, the leaching of toxic additives and persistent organic pollutants from environmental plastics, and their consequences for marine macrofauna are widely reported. However, little is known about the effects of persistent plastic pollution on microbial functioning. Shotgun metagenomics sequencing provides us with the necessary tools to examine broad-scale community functioning to further investigate how plastics influence microbial communities. This study provides insight into the functional consequence of continued exposure to waste plastic by comparing the prokaryotic functional potential of biofilms on five types of plastic [linear low-density polyethylene (LLDPE), nylon-6, polyethylene terephthalate, polylactic acid, and oxygen-degradable LLDPE], glass, and ambient pond water over 12 months and at different depths (20, 40, and 60 cm) within a tertiary maturation pond of a municipal wastewater treatment plant.

Chronic polystyrene microplastics exposure-induced changes in thick-shell mussel (Mytilus coruscus) metaorganism: A holistic perspective

Microplastics have emerged as a significant global concern, particularly in marine ecosystems. While extensive research has focused on the toxicological effects of microplastics on marine animals and/or their associated microorganisms as two separate entities, the holistic perspective of the adaptability and fitness of a marine animal metaorganism-comprising the animal host and its microbiome-remains largely unexplored. In this study, mussel metaorganisms subjected chronic PS-MPs exposure experienced acute mortality but rapidly adapted. We investigated the response of innate immunity, digestive enzymes and their associated microbiomes to chronic PS-MPs exposure. We found that PS-MPs directly and indirectly interacted with the host and microbe within the exposure system. The adaptation was a joint effort between the physiological adjustments of mussel host and genetic adaptation of its microbiome. The mussel hosts exhibited increased antioxidant activity, denser gill filaments and increased immune cells, enhancing their innate immunity. Concurrently, the gill microbiome and the digestive gland microbiome respective selectively enriched for plastic-degrading bacteria and particulate organic matter-utilizing bacteria, facilitating the microbiome's adaptation. The microbial adaptation to chronic PS-MPs exposure altered the ecological roles of mussel microbiome, as evidenced by alterations in microbial interactions and nutrient cycling functions. These findings provided new insights into the ecotoxicological impact of microplastics on marine organisms from a metaorganism perspective.

Microbiomes on microplastics versus natural microcarriers: Stability and transformation during aquatic travel from aquaculture ponds to adjacent stream

Microplastics (MPs) with different physical-chemical properties are considered as vectors for the propagation of microbes in aquatic environments. It remains unclear how plastic types impact on the plastisphere and whether different MPs spread microbes more rapidly than natural materials in microbes across distinct water bodies as proposed previously. We used in-situ incubation to investigate the microbes attached on MPs of polyethylene (PE), polypropylene (PP), and polyvinyl chloride (PVC), versus that on two natural microcarriers (quartz sands and bamboo) during the travel from aquaculture ponds with impacted by fish farming to adjacent freshwater stream. The results showed that the microbial communities on the carriers were shaped not only by environmental conditions, which were primary determinants but also by carrier types. All the tested plastics did not carry more microbes than the natural carriers during the journey. The biofilm community composition on PVC is distinct from that on PE and PP MPs and natural carriers. The plastisphere of PE and PP kept microbial proportions as natural materials did but PVC retained less than nature materials. Bamboo carried more potential pathogens than plastic polymers and quartz. The results indicated that the communities of plastisphere is polymer-type dependent, and, compared with the natural materials, MPs did not show enhanced propagation of microbes, including pathogens, cross distinct environments.

Structural properties and microbial diversity of the biofilm colonizing plastic substrates in Terra Nova Bay (Antarctica)

Microbial colonization on plastic polymers has been extensively explored, however the temporal dynamics of biofilm community in Antarctic environments are almost unknown. As a contribute to fill this knowledge gap, the structural characteristics and microbial diversity of the biofilm associated with polyvinyl chloride (PVC) and polyethylene (PE) panels submerged at 5 m of depth and collected after 3, 9 and 12 months were investigated in four coastal sites of the Ross Sea. Additional panels placed at 5 and 20 m were retrieved after 12 months. Chemical characterization was performed by FTIR-ATR and Raman (through Surface-Enhanced Raman Scattering, SERS) spectroscopy. Bacterial community composition was quantified at a single cell level by Catalyzed Reporter Deposition Fluorescence In Situ Hybridization (CARD-FISH) and Confocal Laser Scanning Microscopy (CLSM); microbial diversity was assessed by 16S rRNA gene sequencing. This multidisciplinary approach has provided new insights into microbial community dynamics during biofouling process, shedding light on the biofilm diversity and temporal succession on plastic substrates in the Ross Sea. Significant differences between free-living and microbial biofilm communities were found, with a more consolidated and structured community composition on PVC compared to PE. Spectral features ascribable to tyrosine, polysaccharides, nucleic acids and lipids characterized the PVC-associated biofilms. Pseudomonadota (among Gamma-proteobacteria) and Alpha-proteobacteria dominated the microbial biofilm community. Interestingly, in Road Bay, close to the Italian "Mario Zucchelli" research station, the biofilm growth - already observed during summer season, after 3 months of submersion - continued afterwards leading to a massive microbial abundance at the end of winter (after 12 months). After 3 months, higher percentages of Gamma-proteobacteria in Road Bay than in the not-impacted site were found. These observations lead us to hypothesize that in this site microbial fouling developed during the first 3 months could serve as a starter pioneering community stimulating the successive growth during winter.

Biofilms in plastisphere from freshwater wetlands: Biofilm formation, bacterial community assembly, and biogeochemical cycles

Microorganisms can colonize to the surface of microplastics (MPs) to form biofilms, termed "plastisphere", which could significantly change their physiochemical properties and ecological roles. However, the biofilm characteristics and the deep mechanisms (interaction, assembly, and biogeochemical cycles) underlying plastisphere in wetlands currently lack a comprehensive perspective. In this study, in situ biofilm formation experiments were performed in a park with different types of wetlands to examine the plastisphere by extrinsic addition of PVC MPs in summer and winter, respectively. Results from the spectroscopic and microscopic analyses revealed that biofilms attached to the MPs in constructed forest wetlands contained the most abundant biomass and extracellular polymeric substances. Meanwhile, data from the high-throughput sequencing showed lower diversity in plastisphere compared with soil bacterial communities. Network analysis suggested a simple and unstable co-occurrence pattern in plastisphere, and the null model indicated increased deterministic process of heterogeneous selection for its community assembly. Based on the quantification of biogeochemical cycling genes by high-throughput qPCR, the relative abundances of genes involving in carbon degradation, carbon fixation, and denitrification were significantly higher in plastisphere than those of soil communities. This study greatly enhanced our understanding of biofilm formation and ecological effects of MPs in freshwater wetlands.

Biocontrol agents modulate phyllosphere microbiota interactions against pathogen Pseudomonas syringae

The pathogen Pseudomonas syringae, responsible for a variety of diseases, poses a considerable threat to global crop yields. Emerging biocontrol strategies employ antagonistic microorganisms, utilizing phyllosphere microecology and systemic resistance to combat this disease. However, the interactions between phyllosphere microbial dynamics and the activation of the plant defense system remain poorly understood. Here we show significant alterations in phyllosphere microbiota structure and plant gene expression following the application of biocontrol agents. We reveal enhanced collaboration and integration of Sphingomonas and Methylobacterium within the microbial co-occurrence network. Notably, Sphingomonas inhibits P. syringae by disrupting pathogen chemotaxis and virulence. Additionally, both Sphingomonas and Methylobacterium activate plant defenses by upregulating pathogenesis-related gene expression through abscisic acid, ethylene, jasmonate acid, and salicylic acid signaling pathways. Our results highlighted that biocontrol agents promote plant health, from reconstructing beneficial microbial consortia to enhancing plant immunity. The findings enrich our comprehension of the synergistic interplays between phyllosphere microbiota and plant immunity, offering potential enhancements in biocontrol efficacy for crop protection.

Plastisphere Microbiomes Respiring Persistent Organohalide Pollutants

Plastics are invading nearly all ecosystems on earth, acting as emerging repositories for toxic organic pollutants and thereby imposing substantial threats to ecological integrity. The colonization of plastics by microorganisms, forming the plastisphere, has garnered attention due to its potential influence on biogeochemical cycles. However, the capability of plastisphere microorganisms to attenuate organohalide pollutants remains to be evaluated. This study revealed that the plastisphere, collected from coastal ecosystems, harbors unique microbiomes, while the natural accumulation of organohalide pollutants on plastics may favor the proliferation of organohalide-respiring bacteria (OHRB). Laboratory tests further elucidated the high potential of plastisphere microbiota to reductively dehalogenate a variety of organohalide pollutants. Notably, over 70% tested plastisphere completely debrominated tetrabromobisphenol A (TBBPA) and polybrominated diphenyl ethers (PBDEs) to nonhalogenated products, whereas polychlorinated biphenyls (PCBs) were converted to lower congeners under anaerobic conditions. Dehalococcoides, Dehalogenimonas, and novel Dehalococcoidia populations might contribute to the observed dehalogenation based on their growth during incubation and positive correlations with the quantity of halogens removed. Intriguingly, large fractions of these OHRB populations were identified in a lack of the currently known TBBPA/PBDEs/PCBs reductive dehalogenase (RDase) genes, suggesting the presence of novel RDase genes. Microbial community analyses identified organohalides as a crucial factor in determining the composition, diversity, interaction, and assembly of microbes derived from the plastisphere. Collectively, this study underscores the overlooked roles of the plastisphere in the natural attenuation of persistent organohalide pollutants and sheds light on the unignorable impacts of organohalide compounds on the microbial ecology of the plastisphere.

Colonization characteristics and surface effects of microplastic biofilms: Implications for environmental behavior of typical pollutants

This paper summarizes the colonization dynamics of biofilms on microplastics (MPs) surfaces in aquatic environments, encompassing bacterial characteristics, environmental factors affecting biofilm formation, and matrix types and characteristics. The interaction between biofilm and MPs was also discussed. Through summarizing recent literatures, it was found that MPs surfaces offer numerous benefits to microorganisms, including nutrient enrichment and enhanced resistance to environmental stress. Biofilm colonization changes the surface physical and chemical properties as well as the transport behavior of MPs. At the same time, biofilms also play an important role in the fragmentation and degradation of MPs. In addition, we also investigated the coexistence level, adsorption mechanism, enrichment, and transformation of MPs by environmental pollutants mediated by biofilms. Moreover, an interesting aspect about the colonization of biofilms was discussed. Biofilm colonization not only had a great effect on the accumulation of heavy metals by MPs, but also affects the interaction between particles and environmental pollutants, thereby changing their toxic effects and increasing the difficulty of MPs treatment. Consequently, further attention and research are warranted to delve into the internal mechanisms, environmental risks, and the control of the coexistence of MPs and biofilms.

Phototrophs as the central components of the plastisphere microbiome in coastal environments

Upon entering the marine environment, plastics are colonized by a plethora of microorganisms to form a plastisphere, influencing the fate and transport of the plastic debris and the health of marine ecosystems. The assembly of marine plastisphere is generally believed to be dominated by stochastic processes. However, it remains elusive whether microbial interaction in the assembly of plastisphere microbial communities is conserved or not. We analyzed the plastisphere microbiomes of 137 plastic debris samples from intertidal zones at different geographical locations and habitats (seagrass, coral, mangrove, beach, and open ocean) and compared them with the surrounding sediment and seawater microbiomes. Microbial community structures of the plastisphere from different locations were more similar to each other but differed substantially from the surrounding sediment and water microbiomes, implying a common mechanism of plastisphere assembly. We used different machine learning algorithms (Multinomial Logistic Regression, Support Vector Machine, Decision Trees, Random Forest, and Artificial Neural Networks) to classify plastic debris samples with high sensitivity based on the microbiome composition. Eukaryotic and prokaryotic phototrophic organisms such as green algae, diatoms, and cyanobacteria, were found to be enriched on the plastic surfaces. Network analysis revealed the central role of the phototrophic organisms in the formation and sustenance of the plastispheres. We found that phototrophs served as core members interacting strongly with heterotrophic organisms in marine plastisphere, irrespective of the sampling location, habitats, and polymer types. This would explain the stochastic assembly of the plastisphere along with conserved properties driven by the phototrophs in the surrounding environment. Our results highlight the importance of phototrophic organisms in shaping the marine plastisphere microbial communities.

Toxic effects and mechanisms of chronic cadmium exposure on Litopenaeus vannamei growth performance based on combined microbiome and metabolome analysis

Cadmium (Cd) pollution seriously affects marine organisms' health and poses a threat to food safety. Although Cd pollution has attracted widespread attention in aquaculture, little is known about the toxic mechanisms of chronic Cd exposure on shrimp growth performance. The study investigated the combined effects of chronic exposure to Cd of different concentrations including 0, 75, 150, and 300 μg/L for 30 days on the growth performance, tissue bioaccumulation, intestinal microbiology, and metabolic responses of Litopenaeus vannamei. The results revealed that the growth was significantly inhibited under exposure to 150 and 300 μg/L Cd2+. The bioaccumulation in gills and intestines respectively showed an increasing and inverted "U" shaped trend with increasing Cd2+ concentration. Chronic Cd altered the intestinal microflora with a significant decrease in microbial richness and increasing trends in the abundances of the potentially pathogenic bacteria Vibrio and Maribacter at exposure to 75 and 150 μg/L Cd2+, and Maribacter at 300 μg/L. In addition, chronic Cd interfered with intestinal metabolic processes. The expressions of certain metabolites associated with growth promotion and enhanced antioxidant power, including N-methyl-D-aspartic acid, L-malic acid, guanidoacetic acid, betaine, and gluconic acid were significantly down-regulated, especially at exposure to 150 and 300 μg/L Cd2+, and were negatively correlated with Vibrio and Maribacter abundance levels. In summary, chronic Cd exposure resulted in severe growth inhibition and increased Cd accumulation in shrimp tissues. Increased levels of intestinal pathogenic bacteria and decreased levels of growth-promoting metabolites may be the key causes of growth inhibition. Harmful bacteria Vibrio and Maribacter may be associated with the inhibition of growth-promoting metabolite expression and may be involved in disrupting intestinal metabolic functions, ultimately impairing shrimp growth potential. This study sheds light on the potential toxicological mechanisms of chronic Cd inhibition on shrimp growth performance, offering new insights into Cd toxicity studies in aquaculture.

The assembly and ecological roles of biofilms attached to plastic debris of Ashmore reef

Plastic pollution in the ocean is a global environmental hazard aggravated by poor management of plastic waste and growth of annual plastic consumption. Microbial communities colonizing the plastic's surface, the plastisphere, has gained global interest resulting in numerous efforts to characterize the plastisphere. However, there are insufficient studies deciphering the underlying metabolic processes governing the function of the plastisphere and the plastic they reside upon. Here, we collected plastic and seawater samples from Ashmore Reef in Australia to examine the planktonic microbes and plastic associated biofilm (PAB) to investigate the ecological impact, pathogenic potential, and plastic degradation capabilities of PAB in Ashmore Reef, as well as the role and impact of bacteriophages on PAB. Using high-throughput metagenomic sequencing, we demonstrated distinct microbial communities between seawater and PAB. Similar numbers of pathogenic bacteria were found in both sample types, yet plastic and seawater select for different pathogen populations. Virulence Factor analysis further illustrated stronger pathogenic potential in PAB, highlighting the pathogenicity of environmental PAB. Furthermore, functional analysis of Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways revealed xenobiotic degradation and fatty acid degradation to be enriched in PABs. In addition, construction of metagenome-assembled genomes (MAG) and functional analysis further demonstrated the presence of a complete Polyethylene (PE) degradation pathway in multiple Proteobacteria MAGs, especially in Rhodobacteriaceae sp. Additionally, we identified viral population presence in PAB, revealing the key role of bacteriophages in shaping these communities within the PAB. Our result provides a comprehensive overview of the various ecological processes shaping microbial community on marine plastic debris.

Distribution, community structure and assembly patterns of phytoplankton in the northern South China Sea

A cruise was conducted in the summer of 2023 from the Pearl River Estuary (PRE) to the adjacent waters of the Xisha Islands in the northern South China Sea (NSCS) to investigate the distribution, community structure, and assembly patterns of eukaryotic and prokaryotic phytoplankton using high-throughput sequencing (HTS) and microscopic observation. Dinophyta were the most abundant phylum in the eukaryotic phytoplankton community based on HTS, accounting for 92.17% of the total amplicon sequence variants (ASVs). Syndiniales was the most abundant order among eukaryotic phytoplankton, whereas Prochlorococcus was the most abundant genus within cyanobacteria. The alpha diversity showed the lowest values in the PRE area and decreased gradually with depth, while cyanobacteria exhibited higher alpha diversity indices in the PRE and at depths ranging from 75 m to 750 m. The morphological results were different from the data based on HTS. Diatoms (37 species) dominated the phytoplankton community, with an average abundance of 3.01 × 104 cells L-1, but only six species of dinoflagellate were observed. Spearman correlation analysis and redundancy analysis (RDA) showed that the distribution and community structure of phytoplankton were largely influenced by geographical location and environmental parameters in the NSCS. The neutral community model (NCM) and null model indicated that deterministic processes played a significant role in the assembly of eukaryotic phytoplankton, with heterogeneous selection and homogeneous selection accounting for 47.27 and 29.95%, respectively. However, stochastic processes (over 60%) dominated the assembly of cyanobacteria and undominated processes accounted for 63.44%. In summary, the formation of eukaryotic phytoplankton was mainly influenced by environmental factors and geographic location, but the assembly of cyanobacteria was shaped by both stochastic processes, which accounted for over 60%, and environmental selection in the NSCS.

Anthropogenic restoration exhibits more complex and stable microbial co-occurrence patterns than natural restoration in rubber plantations

Forest restoration is an effective method for restoring degraded soil ecosystems (e.g., converting primary tropical forests into rubber monoculture plantations; RM). The effects of forest restoration on microbial community diversity and composition have been extensively studied. However, how rubber plantation-based forest restoration reshapes soil microbial communities, networks, and inner assembly mechanisms remains unclear. Here, we explored the effects of jungle rubber mixed (JRM; secondary succession and natural restoration of RM) plantation and introduction of rainforest species (AR; anthropogenic restoration established by mimicking the understory and overstory tree species of native rainforests) to RM stands on soil physico-chemical properties and microbial communities. We found that converting tropical rainforest (RF) to RM decreased soil fertility and simplified microbial composition and co-occurrence patterns, whereas the conversion of RM to JRM and AR exhibited opposite results. These changes were significantly correlated with pH, soil moisture content (SMC), and soil nutrients, suggesting that vegetation restoration can provide a favorable soil microenvironment that promotes the development of soil microorganisms. The complexity and stability of the bacterial-fungal cross-kingdom, bacterial, and fungal networks increased with JRM and AR. Bacterial community assembly was primarily governed by stochastic (78.79 %) and deterministic (59.09 %) processes in JRM and AR, respectively, whereas stochastic processes (limited dispersion) predominantly shaped fungal assembly across all forest stands. AR has more significant benefits than JRM, such as a relatively slower and natural vegetation succession with more nutritive soil conditions, microbial diversity, and complex and stable microbial networks. These results highlight the importance of sustainable forest management to restore soil biodiversity and ecosystem functions after extensive soil degradation and suggest that anthropogenic restoration can more effectively improve soil quality and microbial communities than natural restoration in degraded rubber plantations.

Biofilms on Plastic Debris and the Microbiome

Plastic pollution has become a global environmental problem, and the large number of microorganisms attached to plastic debris in the environment has become a hot topic due to their rapid response to pollutants and environmental changes. In this study, we used high-throughput sequencing to investigate the microbial community structure of and explore the metagenome in the biofilm of two types of plastic debris, polystyrene (PS) and polyethylene terephthalate (PET), and compared them with a water sample collected at the sampling site. The phylum Proteobacteria dominated both the PET and PS samples, at 93.43% and 65.95%, respectively. The metagenome data indicated that the biofilm is enriched with a number of hydrocarbon (petroleum, microplastics, etc.) degrading genes. Our results show that the type of plastic determined the bacterial community structure of the biofilm, while the environment had relatively little effect.

Insight into effect of polyethylene microplastic on nitrogen removal in moving bed biofilm reactor: Focusing on microbial community and species interactions

Microplastics (MPs) pollution has emerged as a global concern, and wastewater treatment plants (WWTPs) are one of the potential sources of MPs in the environment. However, the effect of polyethylene MPs (PE) on nitrogen (N) removal in moving bed biofilm reactor (MBBR) remains unclear. We hypothesized that PE would affect N removal in MBBR by influencing its microbial community. In this study, we investigated the impacts of different PE concentrations (100, 500, and 1000 μg/L) on N removal, enzyme activities, and microbial community in MBBR. Folin-phenol and anthrone colorimetric methods, oxidative stress and enzyme activity tests, and high-throughput sequencing combined with bioinformation analysis were used to decipher the potential mechanisms. The results demonstrated that 1000 μg/L PE had the greatest effect on NH4+-N and TN removal, with a decrease of 33.5 % and 35.2 %, and nitrifying and denitrifying enzyme activities were restrained by 29.5-39.6 % and 24.6-47.4 %. Polysaccharide and protein contents were enhanced by PE, except for 1000 μg/L PE, which decreased protein content by 65.4 mg/g VSS. The positive links of species interactions under 1000 μg/L PE exposure was 52.07 %, higher than under 500 μg/L (51.05 %) and 100 μg/L PE (50.35 %). Relative abundance of some metabolism pathways like carbohydrate metabolism and energy metabolism were restrained by 0.07-0.11 % and 0.27-0.4 %. Moreover, the total abundance of nitrification and denitrification genes both decreased under PE exposure. Overall, PE reduced N removal by affecting microbial community structure and species interactions, inhibiting some key metabolic pathways, and suppressing key enzyme activity and functional gene abundance. This paper provides new insights into assessing the risk of MPs to WWTPs, contributing to ensuring the health of aquatic ecosystems.

Colonization and Biodegradation Potential of Fungal Communities on Immersed Polystyrene vs. Biodegradable Plastics: A Time Series Study in a Marina Environment

Plastic pollution of the ocean is a major environmental threat. In this context, a better understanding of the microorganisms able to colonize and potentially degrade these pollutants is of interest. This study explores the colonization and biodegradation potential of fungal communities on foamed polystyrene and alternatives biodegradable plastics immersed in a marina environment over time, using the Brest marina (France) as a model site. The methodology involved a combination of high-throughput 18S rRNA gene amplicon sequencing to investigate fungal taxa associated with plastics compared to the surrounding seawater, and a culture-dependent approach to isolate environmentally relevant fungi to further assess their capabilities to utilize polymers as carbon sources. Metabarcoding results highlighted the significant diversity of fungal communities associated with both foamed polystyrene and biodegradable plastics, revealing a dynamic colonization process influenced by the type of polymer and immersion time. Notably, the research suggests a potential for certain fungal species to utilize polymers as a carbon source, emphasizing the need for further exploration of fungal biodegradation potential and mechanisms.

Ammonia-oxidizing archaea adapted better to the dark, alkaline oligotrophic karst cave than their bacterial counterparts

Subsurface karst caves provide unique opportunities to study the deep biosphere, shedding light on microbial contribution to elemental cycling. Although ammonia oxidation driven by both ammonia-oxidizing bacteria (AOB) and ammonia-oxidizing archaea (AOA) is well explored in soil and marine environments, our understanding in the subsurface biosphere still remained limited to date. To address this gap, weathered rock and sediment samples were collected from the Xincuntun Cave in Guilin City, an alkaline karst cave, and subjected to high-throughput sequencing and quantification of bacterial and archaeal amoA, along with determination of the potential nitrification rates (PNR). Results revealed that AOA dominated in ammonia oxidation, contributing 48-100% to the PNR, and AOA amoA gene copies outnumbered AOB by 2 to 6 orders. Nitrososphaera dominated in AOA communities, while Nitrosopira dominated AOB communities. AOA demonstrated significantly larger niche breadth than AOB. The development of AOA communities was influenced by deterministic processes (50.71%), while AOB communities were predominantly influenced by stochastic processes. TOC, NH4+, and Cl- played crucial roles in shaping the compositions of ammonia oxidizers at the OTU level. Cross-domain co-occurrence networks highlighted the dominance of AOA nodes in the networks and positive associations between AOA and AOB, especially in the inner zone, suggesting collaborative effort to thrive in extreme environments. Their high gene copies, dominance in the interaction with ammonia oxidizing bacteria, expansive niche breadth and substantial contribution to PNR collectively confirmed that AOA better adapted to alkaline, oligotrophic karst caves environments, and thus play a fundamental role in nitrogen cycling in subsurface biosphere.

Powdery mildew-induced changes in phyllosphere microbial community dynamics of cucumber

As an important habitat for microorganisms, the phyllosphere has a great impact on plant growth and health, and changes in phyllosphere microorganisms are closely related to the occurrence of leaf diseases. However, there remains a limited understanding regarding alterations to the microbial community in the phyllosphere resulting from pathogen infections. Here, we analyzed and compared the differences in phyllosphere microorganisms of powdery mildew cucumber from three disease severity levels (0% < L1 < 30%, 30% ≤ L2 < 50%, L3 ≥ 50%, the number represents the lesion coverage rate of powdery mildew on leaves). There were significant differences in α diversity and community structure of phyllosphere communities under different disease levels. Disease severity altered the community structure of phyllosphere microorganisms, Rosenbergiella, Rickettsia, and Cladosporium accounted for the largest proportion in the L1 disease grade, while Bacillus, Pantoea, Kocuria, and Podosphaera had the highest relative abundance in the L3 disease grade. The co-occurrence network analysis of the phyllosphere microbial community indicated that the phyllosphere bacterial community was most affected by the severity of disease. Our results suggested that with the development of cucumber powdery mildew, the symbiotic relationship between species was broken, and the entire bacterial community tended to compete.

Multi-omics reveals different impact patterns of conventional and biodegradable microplastics on the crop rhizosphere in a biofertilizer environment

Microplastics (MPs) from the incomplete degradation of agricultural mulch can stress the effectiveness of biofertilizers and ultimately affect the rhizosphere environment of crops. Yet, the involved mechanisms are poorly known and robust empirical data is generally lacking. Here, conventional polyethylene (PE) MPs and poly(butylene adipate-co-butylene terephthalate) (PBAT) / poly(lactic acid) (PLA) biodegradable MPs (PBAT-PLA BioMPs) were investigated to assess their potential impact on the rhizosphere environment of Brassica parachinensis in the presence of Bacillus amyloliquefaciens biofertilizer. The results revealed that both MPs caused different levels of inhibited crop both above- and belowground crop biomass (up to 50.11% and 57.09%, respectively), as well as a significant decrease in plant height (up to 48.63% and 25.95%, respectively), along with an imbalance of microbial communities. Transcriptomic analyses showed that PE MPs mainly affected root's vitamin metabolism, whereas PBAT-PLA BioMPs mainly interfered with the lipid's enrichment. Metabolomic analyses further indicated that PE MPs interfered with amino acid synthesis that involved in crops' oxidative stress, and that PBAT-PLA BioMPs mainly affected the pathways associated with root growth. Additionally, PBAT-PLA BioMPs had a bigger ecological negative impact than did PE MPs, as evidenced by more pronounced alterations in root antioxidant abilities, a higher count of identified differential metabolites, more robust interrelationships among rhizosphere parameters, and a more intricate pattern of impacts on rhizosphere metrics. This study highlights the MPs' impact on crop rhizosphere in a biofertilizer environment from a rhizosphere multi-omics perspective, and has theoretical implications for scientific application of biofertilizers.