The rare biosphere harbors immense microbial diversity, yet most low-abundance taxa remain uncultured and functionally enigmatic. Here, we isolated strain D14T from deep-sea water, and propose to classify it as a novel species, Metabolovarius oceani sp. nov., within the novel family Metabolovariaceae fam. nov. M. oceani represents the first cultivated member of the candidate family NORP267, a globally distributed but elusive alphaproteobacterial lineage known only from metagenome-assembled genomes. It possesses broad metabolic capabilities, including CO2 fixation, polyhydroxyalkanoate biosynthesis, complete denitrification and thiosulfate oxidation, and is capable of aerobic growth under both heterotrophic and autotrophic conditions and of anaerobic autotrophic denitrification via thiosulfate oxidation. Despite its versatile metabolic repertoire and global distribution, Metabolovariaceae remains consistently low in abundance across diverse habitats. The isolation of M. oceani permits direct experimental insights into the evolutionary adaptations, physiological resilience, and potential ecosystem roles of rare but metabolically versatile microorganisms within the microbial dark matter.

Chlorinated paraffins (CPs) are widely used, structurally complex mixtures of chlorinated alkanes whose ecological risks in aquatic ecosystems have raised increasing concern. However, the toxic effects and molecular mechanisms of CPs on primary aquatic producers remain poorly understood. In this study, we used the eukaryotic green algae Chlorella sp. and the prokaryotic cyanobacterium Microcystis aeruginosa (M. aeruginosa) as test organisms to systematically investigate the effects of CPs with different carbon chain lengths, namely short-chain CPs (SCCPs), medium-chain CPs (MCCPs), and long-chain CPs (LCCPs), on algal growth, photosynthetic pigment content, antioxidant systems, cellular ultrastructure, and the underlying molecular responses. Our results showed that CPs toxicity to algae is significantly dependent on both CPs carbon-chain length and algal species. Exposure to 1.0 mg/L SCCPs for 96 h produced a growth inhibition of Chlorella sp. of 14.45%. CPs’ exposure significantly altered algal Chl-a content and elicited antioxidant defense responses, and affected the synthesis and extracellular release of MC-RR and MC-LR in M. aeruginosa. Ultrastructural observations revealed cell surface wrinkling and deformation in both Chlorella sp. and M. aeruginosa. Chlorella sp. additionally exhibited thylakoid disintegration and plasmolysis. Transcriptomic analysis indicated that CPs with different chain lengths significantly downregulated genes in Chlorella sp. associated with DNA replication and mismatch repair, suggesting impairment of replication initiation and elongation and compromised genome stability. Concurrently, genes encoding photosynthetic antenna proteins and carbon fixation were upregulated. In M. aeruginosa, CPs exposure markedly disturbed energy metabolism pathways, including glycolysis/gluconeogenesis and oxidative phosphorylation, which were generally downregulated. This study provides a comparative assessment of CPs’ toxicity between the eukaryotic algae Chlorella sp. and the prokaryotic algae M. aeruginosa, revealing that toxicity is co-determined by carbon chain length and algal species. Additionally, it provides critical toxicological data and establishes a theoretical foundation for the scientific assessment of the aquatic ecological risks posed by CPs with different carbon chain lengths.

Microplastics (MPs), as emerging contaminants, are increasingly prevalent in the environment, posing significant threats to ecosystems and human health. However, the ecological risks associated with different polymer types, particularly their toxic effects and underlying molecular mechanisms on cyanobacteria, remain poorly understood. This study comprehensively investigated the toxicological impacts of four common MPs—polyethylene (PE), polystyrene (PS), polyvinyl chloride (PVC), and polytetrafluoroethylene (PTFE)—on Microcystis aeruginosa (M. aeruginosa) over a 12-day exposure period. Results showed that all four MPs significantly inhibited M. aeruginosa growth, with maximum inhibition rates of 68.3 % (50 mg/L PE, day 6), 61.0 % (50 mg/L PS, day 4), 68.2 % (200 mg/L PVC, day 8), and 63.3 % (100 mg/L PTFE, day 6), respectively. Additionally, MPs exposure led to reduced chlorophyll content, impaired photosynthetic activity, and induced oxidative stress, though these effects exhibited temporal dynamics and partial reversibility. Integrated transcriptomic and physiological analyses revealed polymer-specific mechanisms: PE, PVC, and PTFE primarily disrupted M. aeruginosa growth by targeting ABC transporter and oxidative phosphorylation pathways, whereas PS affected ABC transporter and amino sugar and nucleotide sugar metabolism pathways. This study elucidates the toxicological mechanisms of different MP polymer types and provides critical insights for assessing their ecological risks.

Deep-sea microorganisms comprise the Earth's largest and least explored microbiome, yet the vast majority remain uncultivated due to challenges of preserving in situ high hydrostatic pressure and preventing loss of viability and diversity during recovery, which limits our ability to explore their ecological functions and adaptive strategies. Here, we introduce DeepDrop, a microfluidics platform that enables high-throughput single-cell cultivation under pressures spanning the full ocean depth directly aboard research vessels, following direct colony formation via pipette-generated double emulsions. Applying to hadal samples, DeepDrop recovered >50% more microbial diversity than conventional high-pressure bulk cultivation, including rare taxa with streamlined genomes and distinctive genetic features associated with pressure adaptation. Combined metagenomic and transcriptomic analyses revealed that DeepDrop enriched pressure-adapted taxa carrying key stress-related genes and induced coordinated transcriptional reprogramming, characterized by upregulation of stress pathways and repression of motility. By integrating shipboard deployment, pressure-stable droplet cultivation, and efficient recovery, DeepDrop offers a powerful platform for accessing deep-sea microbial dark matter and illuminating microbial life strategies under extreme environmental constraints.

Uncultured UBA5794 actinobacteria are frequently found in marine and inland water environments by using metagenomic approaches. However, knowledge about these actinobacteria is limited, hindering their isolation and cultivation, and they are always confused with “Candidatus Actinomarinales” based on 16S rRNA gene classification. Here, to conduct genomic characterization of them, we obtained three high-quality UBA5794 metagenome-assembled genomes (MAGs) from a hydrothermal sediment on the Carlsberg Ridge (CR) and retrieved 131 high-quality UBA5794 genomes from public datasets. Phylogenomic analysis confirms UBA5794 as an independent order within the class Acidimicrobiia. Genome-based metabolic predictions reveal that flexible metabolism and diversified energy acquisition, as well as heavy metal(loid) detoxification capacity, are crucial for the ability of UBA5794 to thrive in diverse environments. Moreover, there is separation between sponge-associated and free-living UBA5794 groups in phylogeny and functional potential, which can be attributed to the symbiotic nature of the sponge-associated group and the extensive horizontal gene transfer (HGT) events observed in these bacteria. Ancestral state reconstruction suggests that the UBA5794 clade may have originated from a free-living environment and then some members gradually migrated to the sponge host. Overall, our study sheds light on the ecological adaptation and evolutionary history of the ubiquitous but poorly understood UBA5794 actinobacteria.

The proliferation of antibiotics, driven by rapid advancements in medical treatment and animal husbandry, has led to widespread environmental contamination and ecological concerns. In this study, we compared the response mechanisms of the eukaryotic microalga Chlorella sp. and the prokaryotic cyanobacterium Microcystis aeruginosa to sulfanilamide (SD). SD exposure stimulated the overall growth of Chlorella sp. but inhibited M. aeruginosa. With increasing SD concentration, the chlorophyll a (Chl-a) content in Chlorella sp. exhibited an initial slight decline followed by an increase. In contrast, Chl-a content in M. aeruginosa decreased linearly with rising SD concentration, culminating in a significant 57.9 % reduction at 100.0 mg/L (p < 0.05). At 1.0 mg/L SD, both species activated antioxidant defense mechanisms to mitigate reactive oxygen species induced damage, and both showed significant increases in soluble protein content (p < 0.05). Notably, M. aeruginosa additionally exhibited increased production of the toxin microcystin-LR. Under 100.0 mg/L SD, Chlorella sp. cells displayed pronounced surface wrinkling and structural collapse, indicative of irreversible cellular damage. Conversely, the structural integrity of M. aeruginosa remained comparatively less compromised under equivalent treatment. Transcriptomic analysis revealed that Chlorella sp. significantly upregulated genes involved in porphyrin metabolism and carbon fixation pathways, enhancing chlorophyll biosynthesis and CO2 assimilation under SD stress. In contrast, M. aeruginosa downregulated genes associated with ABC transporters, sulfur metabolism, and the endoplasmic reticulum folding factor small heat shock factor, likely impairing sulfide and glutathione synthesis, promoting misfolded protein accumulation, exacerbating cellular stress, and inhibiting growth. This study elucidates fundamental differences in the sensitivity and adaptive strategies of phylogenetically distinct algae (eukaryotic vs. prokaryotic) to antibiotic stress.

Microplastics (MPs) have become ubiquitous pollutants in diverse ecosystems, with aquatic environments increasingly identified as major sinks. Nevertheless, the ecological risks and toxic effects of MPs on submerged macrophytes remain poorly understood. This study examined the impacts of three common MPs including polyvinyl chloride (PVC), polystyrene (PS) and polyethylene (PE) at varying concentrations (10 mg/L; 50 mg/L; 100 mg/L) on two submerged plant, Vallisneria natans (V. natans) and Myriophyllum verticillatum (M. verticillatum). The results demonstrated that MPs significantly inhibited the growth of submerged macrophytes, triggered antioxidant responses, and caused membrane damage. Metabolomics analysis revealed that PVC MPs disrupted key metabolic pathways, including pyrimidine metabolism, alanine, aspartate, and glutamate metabolism, as well as β-alanine degradation in V. natans. Furthermore, MPs reduced dissolved oxygen (DO) and oxidation-reduction potential (ORP) levels in the water, promoting the proliferation of Bacteroidetes, Firmicutes, and Chloroflexi in sediments and biofilms. These findings suggest that the toxic mechanisms of MPs on submerged macrophytes primarily involve water quality degradation, shifts in the abundance of dominant microorganisms in sediments and biofilms, and the induction of physiological and metabolic disturbances within the plants. The study provides new insights into the broader ecological implications of MPs in aquatic ecosystems.

Despite the significant importance of bioconversion in coal seams by indigenous microorganisms, a comparative study of microbial diversity on a global scale has not yet been reported, even with the immense advantages offered by ultra-high-throughput sequencing.. In this study, we conducted a comprehensive co-analysis of 16S rRNA gene amplicon sequencing data generated in this study alongside the data from publicly available datasets (including both pyrosequencing and Illumina sequencing) with an aim to investigate microbiome profiles and assess their potential roles in carbon, nitrogen, sulfur, and methane transformations during biogeochemical degradation across diverse regional coal seams. The results revealed significant variations in microbial diversity across different regions. However, the major phyla responsible for the macromolecule breakdown, which include Firmicutes, Proteobacteria, Actinobacteriota, Bacteroidota and Campylobacterota, are consistently present across all samples. The discrepancies in microbial diversities at genus level and metabolic features among regions, are observed to be correlated with coal ranks, physiochemical parameters and geology of the in-situ conditions, indicating a combined effect of environmental selection. Furthermore, we have enhanced the Coal Seam Microbiome (CSMB) Reference Dataset by significantly increasing the number of Operational Taxonomic Units (OTUs). The previous version, CSMB reference dataset V1.0, contained 5,305 OTUs, which has now been upgraded to 8,660 OTUs in CSMB reference dataset V2.0. This substantial increase greatly enriches the microbiome database, enabling more comprehensive and robust comparative analyses across coal seam ecosystems. The present investigation of the coal seam microbiome is anticipated to significantly advance our understanding of the microbial ecology within deep coal reservoirs and provide prospective strategies for optimizing biogas production.

Although homologs of the eukaryotic Urm1 (ubiquitin-related modifier-1) have been characterized in Archaea, the bona fide substrates and roles of the archaeal Urm1 remain poorly understood. Here, we report a proteomic analysis of Urm1 modification in Saccharolobus islandicus using a highly efficient method, which involves the introduction of an H81R substitution into Urm1 encoded by the strain, treatment of the strain with the proteasome inhibitor bortezomib, and affinity enrichment of urmylated peptides with an anti-K-ε-Gly-Gly antibody following peptide fractionation. Extensive protein urmylation was observed, with a total of 783 Urm1 conjugation sites, mapped to 330 proteins, identified in the cell. Among the seven lysine residues in Urm1, six were sites of modification, of which K7 and K37 were preferentially modified. Treatment with the proteasome inhibitor bortezomib resulted in K37-linked chains being the sole major modification species, suggesting that K37 linkage served as a primary trigger of proteasomal degradation. The modified proteins were involved in a number of cellular processes, such as cell division, chromosomal organization, DNA replication, translation, proteasomal protein degradation, and sulfur relay. Protein urmylation was dynamic and influenced by growth conditions and stress treatments. Attempts to delete urm1 were unsuccessful, pointing to the essentiality of the gene. The knockdown of urm1 resulted in substantial growth delay, during which a drastic reduction in cellular concentration of cell division proteins (CdvB, CdvB1, CdvB2) occurred. Our results shed significant light on the landscape and potential roles of protein urmylation in Archaea.IMPORTANCEAlthough protein urmylation has been documented in Archaea for over a decade, the authentic substrates and functional roles of archaeal Urm1 remain largely unknown. In this study, we generated the largest Urm1 modification data set in Archaea through an efficient in vivo approach and investigated its physiological functions in Saccharolobus islandicus. Extensive protein urmylation was observed, with modified proteins implicated in key cellular processes such as cell division, chromosomal organization, translation, and proteasomal degradation. Our findings challenge the prevailing notion that Urm1 homologs modify only a limited number of substrates. Six out of seven lysine residues in Urm1 were modified, suggesting the presence of diverse Urm1 chain structures. These results provide cellular evidence supporting the hypothesis that eukaryotic Ub/Ubl systems have an archaeal origin. We also explored how various factors affect global protein urmylation and examined the impact of urm1 knockdown on cell growth.

The persistence of per- and polyfluoroalkyl substances (PFAS) in surface water can pose risks to ecosystems, while due to data limitations, the occurrence, risks, and future trends of PFAS at large scales remain unknown. This study investigated the ecological risks of PFAS in surface water in China under different Shared Socioeconomic Pathways (SSPs) using machine learning modeling, based on concentration data collected from 167 published papers. The results indicated that long-chain PFAS currently dominated in most basins and posed significant risks, especially PFOA. Population density and temperature were key factors influencing risks of long-chain PFAS, while secondary industry and precipitation affected the risks of PFBS and PFHxS significantly, respectively. In the future, the ecological risks of long-chain PFAS would overall decrease, with risk probabilities of PFOA and PFOS decreasing significantly in SSP5 (8.15 % and 14.95 % reduction compared to 2020, respectively). The risks of short-chain PFAS were expected to increase, but stabilize in the late stage of SSP1. Nevertheless, the risks of long-chain PFAS would remain higher than those of short-chain PFAS, with high-risk areas concentrated in Southeast China. This study suggests changes in ecological risks of PFAS driven by future climate and human activities, providing new insights for risk management.

Seamounts are critical marine biodiversity hot spots, while the metabolic activity of their microbial community remains largely unknown. In this study, we investigated the diversity and activity of free-living and particle-attached microorganisms in the surface, middle, and bottom layers of seawater at the Zhenbei seamount in the South China Sea using omics approaches, including 16S ribosomal RNA (rRNA)/16S rDNA ratio analysis. Over 20 phyla were detected, with Proteobacteria, Actinobacteriota, Cyanobacteria, Bacteroidota, Thaumarchaeota, and Planctomycetota being predominant. Surprisingly, Bdellovibrionota and Myxococcota, the two well-known predatory bacteria, exhibited exceptionally higher rRNA/rDNA ratios than the other phyla, with rRNA abundances being 10- or even 200-fold higher than their rDNA abundances. These metabolically active predatory bacteria are mainly uncultured species. A total of 23 Myxococcota metagenome-assembled genomes (MAGs) and 12 Bdellovibrionota MAGs were assembled. The most highly overexpressed genes frequently detected in these MAGs were those that encode flagellum and pilus proteins as well as T4-like virus tail tube protein, indicating that these predator bacteria were likely active in hunting. Our results suggest that seamounts may serve as hunting grounds for predatory bacteria, which may be involved in controlling the flows of elements and energy in the seamount microbial communities and, thus, in shaping the seamount ecosystems.

C2H2-type zinc finger protein (C2H2-ZFP) transcription factors play evident roles in regulating plant growth and development and abiotic stress responses. However, the role of C2H2-ZFP from Mentha canadensis remains uncertain. We identified the multifunctional C2H2-ZFP gene McZFP1 from M. canadensis based on phylogenetic analysis. The McZFP1 gene was highly expressed in stems, responding to abiotic stress and phytohormone treatments. McZFP1 localized in the nucleus and showed no transcriptional autoactivation activity in yeast. McZFP1 overexpression in Arabidopsis thaliana significantly reduced the number of trichomes and root hairs, root hair length, and salt stress tolerance. Further study revealed that McZFP1 overexpression increased the expression of negative regulator genes and decreased that of positive regulator genes to inhibit plant trichome and root hair development. Malondialdehyde accumulation was promoted, but the proline content and catalase, superoxide dismutase, and peroxidase activities were reduced and the expression of stress response genes was inhibited in McZFP1 overexpression lines under salt treatment, thereby compromising plant salt tolerance. Overall, these results indicate that McZFP1 is a novel C2H2-ZFP transcription factor that plays negative roles in trichome and root hair development and salt stress tolerance.

Hydrogenedentota, a globally distributed bacterial phylum-level lineage, is poorly understood. Here, we established a comprehensive genomic catalog of Hydrogenedentota, including a total of seven clades (or families) with 179 genomes, and explored the metabolic potential and evolutionary history of these organisms. We show that a single genome, especially those belonging to Clade 6, often encodes multiple hydrogenases with genomes in Clade 2, which rarely encode hydrogenases being the exception. Notably, most members of Hydrogenedentota contain a group A3 [FeFe]-hydrogenase (BfuABC) with a non-canonical electron bifurcation mechanism, in addition to substrate-level phosphorylation and electron transport-linked phosphorylation pathways, in energy conservation. Furthermore, we show that BfuABC from Hydrogenedentota fall into five sub-types. Phylogenetic analysis reveals five independent routes for the evolution of BfuABC homologs in Hydrogenedentota. We speculate that the five sub-types of BfuABC might be acquired from Bacillota (synonym Firmicutes) through separate horizontal gene transfer events. These data shed light on the diversity and evolution of bifurcating [FeFe]-hydrogenases and provide insight into the strategy of Hydrogenedentota to adapt to survival in various habitats. IMPORTANCE The phylum Hydrogenedentota is widely distributed in various environments. However, their physiology, ecology, and evolutionary history remain unknown, primarily due to the limited availability of the genomes and the lack of cultured representatives of the phylum. Our results have increased the knowledge of the genetic and metabolic diversity of these organisms and shed light on their diverse energy conservation strategies, especially those involving electron bifurcation with a non-canonical mechanism, which are likely responsible for their wide distribution. Besides, the organization and phylogenetic relationships of gene clusters coding for BfuABC in Hydrogenedentota provide valuable clues to the evolutionary history of group A3 electron bifurcating [FeFe]-hydrogenases.

Short-chain Perfluorinated compounds (PFCs), used as substitutes for highly toxic long-chain PFCs, are increasingly entering the aquatic environment. However, the toxicity of short-chain PFCs in the environment is still controversial. This study investigated the effects of short-chain perfluorobutanesulfonic acid (PFBS) at different concentrations (2.5, 6, 14.4, 36, and 90mg/L) on M. aeruginosa growth under 12-day exposure and explored the molecular mechanism of toxicity using transcriptomics. The results showed that M. aeruginosa exhibited hormetic effects after exposure to PFBS. Low PFBS concentrations stimulated algal growth, whereas high PFBS concentrations inhibited it, and this inhibitory effect became progressively more pronounced with increasing PFBS exposure concentrations. Transcriptomics showed that PFBS promoted the pathways of photosynthesis, glycolysis, energy metabolism and peptidoglycan synthesis, providing the energy required for cell growth and maintaining cellular morphology. PFBS, on the other hand, caused growth inhibition in algae mainly through oxidative stress, streptomycin synthesis, and genetic damage. Our findings provide new insights into the toxicity and underlying mechanism of short-chain PFCs on algae and inform the understanding of the hormetic effect of short-chain PFCs, which are crucial for assessing their ecological risks in aquatic environments.

Hydrogen sulfide (H2S) is a typical odour compound mainly causing respiratory and central nervous system symptoms. However, the immunotoxicity of inhaled H2S and the underlying mechanisms remain largely unknown. In this study, a low-dose inhalation exposure to H2S was arranged to observe inflammatory response and immunotoxicity in lung tissue of rats. Low concentrations of H2S exposure affected the immune level of pulmonary tissue and peripheral blood. Significant pathological changes in lung tissue in the exposure group were observed. At low concentration, H2S not only induced the upregulation of AQP-4 and MMP-9 expression but also stimulated immune responses, initiating various anti-inflammatory and inflammatory factors, altering tissue homeostatic environments. The TNF and chemokine signaling pathway played an important role which can promote the deterioration of pulmonary inflammatory processes and lead to lung injury and fibrosis. Excessive immune response causes an inflammatory effect and blood-gas barrier damage. These data will be of value in evaluating future occupational health risks and providing technical support for the further development of reliable, sensitive, and easy-to-use screening indicators of exposure injury.

Most PAHs produced by human activities can be absorbed and accumulated by edible organisms and pose a potential hazard to human health. However, the source apportionment and human health risk of PAHs accumulated in edible organisms remains largely unknown. Therefore, we conducted source analysis and health risk assessment based on the PAH concentrations in ten marine fish from coastal areas of Guangdong, China. Results showed that the pollution of PAHs in fish organisms was at "Minimally polluted" level, and that all marine fish had the ability to accumulate PAHs. Risk assessment indicated Carcinogenic risk of PAHs in four populations was at a "Cautionary risk" level, with urban children suffered the highest risk. Petroleum pollution, Coal and biomass combustion, and Marine transport emissions were identified as the main anthropogenic sources for PAHs in organisms, and Marine transport emissions accounted for the highest Carcinogenic risk. The Acceptable daily intake for all populations were far below their actual daily intake without causing "Cautionary risk". Our findings provide new insights into the source apportionment and health risk of PAHs from a "source-organism-human" perspective, and suggested that joint management of three anthropogenic sources would be an effective way to prevent the health risks of PAHs.

Climate change and anthropogenic activities are increasingly threatening estuarine and coastal zones. These effects lead to complex positive and negative feedback among sustainable development pillars of human, society, economy and environment according to the integrated sustainability perspective. Only limited studies have calculated comprehensive impact assessments of land conversions between land and sea, invasive species expansion, and inundation impacts on natural wetlands under future scenarios. To fill-in this research gap, this study aims to conduct a long-term temporal analysis (1960–2015) of land use and land cover change (LULC), and future ecosystem service value (ESV) loss for intertidal wetlands predicted in the Yangtze River Estuary (YRE). The results show that, over recent decades, impervious constructed areas and Spartina alterniflora-covered saltmarsh have increased to 10.7% and 2.61%, respectively, whereas native species saltmarshes and tidal flats have decreased to 0.04% and 1.1%, respectively. The total ESV increased significantly during 1960–2000 but significantly declined during 2000–2015. The highest total ESV was US$ 3.8 billion in 2010, considering the approximate contributions of natural and artificial wetlands. Similarly, the ESV of the S. alterniflora saltmarshes reached US$ 0.7 billion in 2015. The total intertidal wetlands area could decrease to 8071–8248/ha by 2100. The total ESV of intertidal wetland ecosystems would decrease by approximately one billion dollars between 2015 and 2050. An enhanced understanding of the economic impacts regarding coastal management, restoration, and conservation is of profound importance for improving coastal resilience, sustainable development, and adaptation of coastal societies to climate change in the Yangtze River Estuary.

As plastic pollution continues to increase and plastic waste is shredded to form smaller plastic particles, there is growing concern about the potential impact of nanoplastics (NPs) on freshwater ecosystems. In this work, the effects of three surface-modified NPs, including polystyrene (PS), PS-NH2, and PS-COOH, on the growth, photosynthetic activity, oxidative damage, and microcystins (MCs) production/release of Microcystis aeruginosa (M. aeruginosa) were investigated. Results indicated that all three NPs significantly inhibited the growth of M. aeruginosa after a 96 h exposure, and the growth inhibition followed the order of PS-NH2 > PS > PS-COOH (p < 0.05). Meanwhile, all three NPs at the concentration of 100 mg/L significantly increased the content of intra-MCs (115 %, 147 %, and 121 % higher than the control, respectively) and extra-MCs (142 %, 175 %, and 151 % higher than the control, respectively) after a 96 h exposure (p < 0.05). Moreover, our findings also suggested that the potential mechanisms of surface-modified PS NPs on M. aeruginosa growth and MCs production/release were associated with physical constraints, photosynthetic activity obstruct, and oxidative damage. Our findings provided direct evidence for different kinds of surface modifications of PS NPs on freshwater algae and improve the understanding of the potential risk of NPs in aquatic ecosystems.

The occurrence of microplastics (MPs) within aquatic ecosystems attracts a major environmental concern. It was demonstrated MPs could cause various ecotoxicological effects on microalgae. However, existing data on the effects of MPs on microalgae showed great variability among studies. Here, we performed a meta-analysis of the latest studies on the effects of MPs on photosynthesis and oxidative stress in microalgae. A total of 835 biological endpoints were investigated from 55 studies extracted, and 37 % of them were significantly affected by MPs. In this study, the impact of MPs against microalgae was concentration-dependent and size-dependent, and microalgae were more susceptible to MPs stress in freshwater than marine. Additionally, we summarized the biological functions of microalgae that are primarily affected by MPs. Under MPs exposure, the content of chlorophyll a (Chl-a) was reduced and electron transfer in the photosynthetic system was hindered, causing electron accumulation and oxidative stress damage, which may also affect biological processes such as energy production, carbon fixation, lipid metabolism, and nucleic acid metabolism. Finally, our findings provide important insights into the effects of MPs stress on photosynthesis and oxidative stress in microalga and enhance the current understanding of the potential risk of MPs pollution on aquatic organisms.

Perfluorinated or polyfluorinated compounds (PFCs) continue entering to the environmental as individuals or mixtures, but their toxicological information remains largely unknown. Here, we investigated the toxic effects and ecological risks of Perfluorooctane sulfonic acid (PFOS) and its substitutes on prokaryotes (Chlorella vulgaris) and eukaryotes (Microcystis aeruginosa). Based on the calculated EC50 values, the results showed that PFOS was significantly more toxic to both algae than its alternatives including Perfluorobutane sulfonic acid (PFBS) and 6:2 Fluoromodulated sulfonates (6:2 FTS), and the PFOS-PFBS mixture was more toxic to both algae than the other two PFC mixtures. The action mode of binary PFC mixtures on Chlorella vulgaris was mainly shown as antagonistic and on Microcystis aeruginosa as synergistic, by using Combination index (CI) model coupled with Monte Carlo simulation. The mean risk quotient (RQ) value of three individual PFCs and their mixtures were all below the threshold of 10-1, but the risk of those binary mixtures were higher than that of PFCs individually because of their synergistic effect. Our findings contribute to enhance the understanding of the toxicological information and ecological risks of emerging PFCs and provide a scientific basis for their pollution control.