Realizing Highly-Ordered Laser-Reduced Graphene for High-Performance Flexible Microsupercapacitor.

Laser reduction of graphene oxide (GO) with direct-write technology is promising to develop miniaturized energy storage devices because of highly flexible, mask-free, and chemical-free merits. However, laser reduction of GO is often accompanied with deflagration (spectacular and violent deoxygenating reaction), leading reduced graphene oxide (rGO) films into brittle and irregular internal structure which is harmful to the applications. Here, a pre-reduction strategy is demonstrated to avoid this deflagration and realize a uniform laser-reduced GO (LrGO) matrix for the application of flexible micro-supercapacitors (MSCs).The pre-reduction process with ascorbic acid decreases the content of oxygen-containing functional groups on GO in advance, and thus relieves gases emission and avoids unconstrained expansion during the laser reduction process. In addition, a self-assembled skeleton with pre-reduced GO (PGO) nanosheets could be constructed which is a more appropriate aforehand framework for laser reduction to establish controllable rGO films with the homogenous porosity. The quasi-solid-state MSCs assembled with laser-reduced PGO exhibit the maximum areal capacitance of 88.32 mF cm-2 , good cycling performance (capacitance retention of 82% after 2000 cycles), and outstanding flexibility (no capacitance degradation after bending for 5000 times). This finding provides opportunities to enhance quality of LrGO which is promising for micro-power devices and beyond.

The inhibition and recovery mechanisms of the diatom Phaeodactylum tricornutum in response to high light stress - A study combining physiological and transcriptional analysis.

By combining physiological/biochemical and transcriptional analysis, the inhibition and recovery mechanisms of Phaeodactylum tricornutum in response to extreme high light stress (1300 µmol photons · m-2  · s-1 ) were elucidated. The population growth was inhibited in the first 24 h and started to recover from 48 h. At 24 h, photoinhibition was exhibited as the changes of PSII photosynthetic parameters and decrease in cellular pigments, corresponding to the downregulation of genes encoding light-harvesting complex and pigments synthesis. Changes in those photosynthetic parameters and genes were kept until 96 h, indicating that the decrease of light absorption abilities might be one strategy for photoacclimation. In the meanwhile, we observed elevated cellular ROS levels, dead cells proportions, and upregulation of genes encoding antioxidant materials and proteasome pathway at 24 h. Those stress-related parameters and genes recovered to the controls at 96 h, indicating a stable intracellular environment after photoacclimation. Finally, genes involving carbon metabolisms were upregulated from 24 to 96 h, which ensured the energy supply for keeping high base and nucleotide excision repair abilities, leading to the recovery of cell cycle progression. We concluded that P. tricornutum could overcome photoinhibition by decreasing light-harvesting abilities, enhancing carbon metabolisms, activating anti-oxidative functions, and elevating repair abilities. The parameters of light harvesting, carbon metabolisms, and repair processes were responsible for the recovery phase, which could be considered long-term adaptive strategies for diatoms under high light stress.

The adsorption and absorption kinetics of BDE-47 by Chlorella sp. and the role of extracellular polymer substances influenced by environmental factors.

Microalgae act as the entrance of polybrominated diphenyl ethers (PBDEs) from abiotic to biotic environments, which controlled the environmental fate of PBDEs in aquatic environments. Combing with typical coastal environmental characteristics including extracellular polymer substances (EPS) enrichment, light limitation and nitrogen starvation, the changes of adsorption and absorption kinetics of BDE-47 by Chlorella sp. and the role of EPS therein were investigated. The results quantified the adsorption and absorption kinetics of BDE-47 by Chlorella sp. cells and fitted it by the Lagergren pseudo first order model. Furthermore, we found the adsorption and absorption kinetics could be changed by the above mentioned environmental factors. To be specific, the total BDE-47 adsorption amounts per microalgal cell were increased as the increase of ambient EPS (proteins or carbohydrates), attributing to the increase of soluble (SL)-EPS contents; increased total BDE-47 adsorption amounts but decreased absorption rates were found under light limitation and nitrogen starvation, which were attributed to increased bound (B)-EPS contents and protein/carbohydrates (P/C) ratios therein, respectively. Therefore, our study elucidated the adsorption and absorption kinetics of PBDEs by microalgae could be influenced by ambient environmental changes, clarified the roles of SL-EPS, B-EPS contents and P/C ratios, providing a solid basis for evaluating the environmental fate of PBDEs in the marine environments.

Paper Device Combining CRISPR/Cas12a and Reverse-Transcription Loop-Mediated Isothermal Amplification for SARS-CoV-2 Detection in Wastewater.

Wastewater-based surveillance of the COVID-19 pandemic holds great promise; however, a point-of-use detection method for SARS-CoV-2 in wastewater is lacking. Here, a portable paper device based on CRISPR/Cas12a and reverse-transcription loop-mediated isothermal amplification (RT-LAMP) with excellent sensitivity and specificity was developed for SARS-CoV-2 detection in wastewater. Three primer sets of RT-LAMP and guide RNAs (gRNAs) that could lead Cas12a to recognize target genes via base pairing were used to perform the high-fidelity RT-LAMP to detect the N, E, and S genes of SARS-CoV-2. Due to the trans-cleavage activity of CRISPR/Cas12a after high-fidelity amplicon recognition, carboxyfluorescein-ssDNA-Black Hole Quencher-1 and carboxyfluorescein-ssDNA-biotin probes were adopted to realize different visualization pathways via a fluorescence or lateral flow analysis, respectively. The reactions were integrated into a paper device for simultaneously detecting the N, E, and S genes with limits of detection (LODs) of 25, 310, and 10 copies/mL, respectively. The device achieved a semiquantitative analysis from 0 to 310 copies/mL due to the different LODs of the three genes. Blind experiments demonstrated that the device was suitable for wastewater analysis with 97.7% sensitivity and 82% semiquantitative accuracy. This is the first semiquantitative endpoint detection of SARS-CoV-2 in wastewater via different LODs, demonstrating a promising point-of-use method for wastewater-based surveillance.

Different effecting mechanisms of two sized polystyrene microplastics on microalgal oxidative stress and photosynthetic responses.

Increasing marine microplastics (MPs) pollution potentially threatens the stability of phytoplankton community structures in marine environments. MPs toxicities to microalgae are largely determined by particle size, while the size-dependent mechanisms are still not fully understood. In this study, two sizes (0.1 µm and 1 µm) of polystyrene (PS) MPs were used as experimental targets to systemically compare their different effecting mechanisms on the marine model diatom Thalassiosira pseudonana with respect to oxidative stress and photosynthesis. The results indicated the toxicity of 1 µm sized MPs was higher than 0.1 µm sized MPs regarding to population growth. In condition of similar microalgal population inhibition rates, we found more enhanced cellular oxidative stress and cell death happened in the 1 µm MPs treatments, which could be linked to higher zeta potential of 1 µm MPs and more severe cell surface damage; microalgal surface light shading and cellular pigments decline were more obvious in the 0.1 µm MPs treatment, which could be linked to high aggregation abilities of 0.1 µm MPs. Gene expressions supported the morphological and physiological findings on the transcriptional level. Environmental related MPs concentrations (5 µg L-1) also aroused gene expression changes of T. pseudonana while more changing genes were found under 0.1 µm MPs than 1 µm MPs. These results provide novel insights into the size-dependent mechanisms of MPs toxicity on marine microalgae, as well as their potential influence on the marine environment.

Improved lithium-ion battery performance by introducing oxygen-containing functional groups by plasma treatment.

Metal sulfides are often used as cathode materials for lithium-ion batteries (LIBs) owing to their high theoretical specific capacity; however, excessively fast capacity decay during charging/discharging and rapid shedding during cycling limits their practical application in batteries. In this study, we proposed a strategy using plasma treatment combined with the solvothermal method to prepare cobalt sulfide (Co1-xS)-carbon nanofibers (CNFs) composite. The plasma treatment could introduce oxygen-containing polar groups and defects, which could improve the hydrophilicity of the CNFs for the growth of the Co1-xS, thereby increasing the specific capacity of the composite electrode. The results show that the composite electrode present a high discharge specific capacity (839 mAh g-1at a current density of 100 mA g-1) and good cycle stability (the capacity retention rate almost 100% at 2000 mA g-1after 500 cycles), attributing to the high conductivity of the CNFs. This study proves the application of plasma treatment and simple vulcanization method in high-performance LIBs.

Combined SRC inhibitor saracatinib and anti-ErbB2 antibody H2-18 produces a synergistic antitumor effect on trastuzumab-resistant breast cancer.

Despite of the effectiveness of the anti-ErbB2 humanized antibody trastuzumab, trastuzumab resistance emerges as a major and common clinical problem. Thus, circumventing trastuzumab resistance has become an urgent need. Recently, Src inhibitor saracatinib has drawn great attention for its key role in trastuzumab response. As shown in our previous study, H2-18, an anti-ErbB2 antibody, could potently induce programmed cell death (PCD) in trastuzumab-resistant breast cancer cells. Here we combined H2-18 and a Src inhibitor, saracatinib, and studied the antitumor activity of this drug combination in trastuzumab-resistant breast cancer cell lines. The results showed that H2-18 and saracatinib could synergistically inhibit cell proliferation of BT-474, SKBR-3, HCC-1954 and HCC-1419 breast cancer cell lines in vitro. H2-18 plus saracatinib could also inhibit the HCC-1954 tumor growth more effectively in vivo than each drug alone. H2-18 plus saracatinib showed a significantly more potent PCD-inducing activity compared with either H2-18 or saracatinib alone. We conclude that enhanced PCD may contribute to the superior antitumor efficacy of this combination therapy. The combination of H2-18 and SRC inhibitor has the potential to be translated into clinic.

Hemicyanine-based high resolution ratiometric near-infrared fluorescent probe for monitoring pH changes in vivo.

Intracellular pH is an important parameter associated with cellular behaviors and pathological conditions. Quantitative sensing pH and monitoring its changes by near-infrared (NIR) fluorescence imaging with high resolution in living systems are essential but challenging due to the lack of effective probes. To achieve good adaptability, in this study, a class of resolution-tunable ratiometric NIR fluorescent probes, which possess a stable NIR hemicyanine skeleton bearing different substituents, are rationally designed and synthesized, enabling detection through noninvasive optical imaging of organisms. Based on the protonation/deprotonation of the hydroxy group, a marked NIR emission shift provides a ratio signal in response to pH. Meanwhile, two states exhibit good photostability, sensitivity and reversibility, conducive to longtime monitoring of persistent pH changes without disturbance of other biological active species. Among the series, NIR-Ratio-BTZ modified with an electron-withdrawing substituent of benzothiazole exhibited the largest emission shift of about 76 nm from 672 to 748 nm with the pH environment changing from acidic to basic, which could be considered as a good candidate for high resolution pH imaging in live cells, tissues and organisms. Moreover, NIR-Ratio-BTZ has an ideal pK(a) value (pK(a) ≈ 7.2) for monitoring the minor fluctuations of physiological pH near neutrality. The ratiometric fluorescence measurement is beneficial to ensure the accuracy of quantitative measuring pH changes, as well as the real-time monitoring pH-related physiological effects both in living cells and living mice. The results demonstrate that NIR-Ratio-BTZ is a highly sensitive ratiometric pH probe in vivo, giving it potential for biological applications.

Selective tracking of lysosomal Cu2+ ions using simultaneous target- and location-activated fluorescent nanoprobes.

Levels of lysosomal copper are tightly regulated in the human body. However, few methods for monitoring dynamic changes in copper pools are available, thus limiting the ability to diagnostically assess the influence of copper accumulation on health status. We herein report the development of a dual target and location-activated rhodamine-spiropyran probe, termed Rhod-SP, activated by the presence of lysosomal Cu(2+). Rhod-SP contains a proton recognition unit of spiropyran, which provides molecular switching capability, and a latent rhodamine fluorophore for signal transduction. Upon activation by lysosomal acidic pH, Rhod-SP binds with Cu(2+) by spiropyran-based proton activation, promoting, in turn, rhodamine ring opening, which shows a "switched on" fluorescence signal. However, to protect Rhod-SP from degradation and interference by the physiological environment, it is engineered on mesoporous silica nanoparticles (MSNs), and the surface of Rhod-SP@MSNs is further anchored with ß-cyclodextrin (ß-CD) to enhance the solubility and bioavailability of Rhod-SP@MSN-CD. Next, to enhance cell specificity, a guiding unit of c(RGDyK) peptide conjugated adamantane (Ad-RGD) as prototypical system, is incorporated on the surface of Rhod-SP@MSN-CD to target integrin αvß3 and αvß5 overexpressed on cancer cells. Fluorescence imaging showed that both Rhod-SP@MSN-CD and Rhod-SP@MSN-CD-RGD were suitable for visualizing exogenous and endogenous Cu(2+) in lysosomes of living cells. This strategy addresses some common challenges of chemical probes in biosensing, such as spatial resolution in cell imaging, the solubility and stability in biological system, and the interference from intracellular species. The newly designed nanoprobe, which allows one to track, on a location-specific basis, and visualize lysosomal Cu(2+), offers a potentially rich opportunity to examine copper physiology in both healthy and diseased states.

Design of a simultaneous target and location-activatable fluorescent probe for visualizing hydrogen sulfide in lysosomes.

Molecular tools capable of providing information on a target analyte in an organelle of interest are especially appreciated. Traditionally, organelle-targetable probes are designed by incorporating an organelle-specific guiding unit to target the probe molecules into the organelle. The imperfect targeting function of the guiding unit and nonspecific distribution of the analyte in cytosol and each organelle would lead to low spatiotemporal resolution and limited sensitivity. To solve this problem, we report herein a new approach for detection of a target analyte in a specific organelle by engineering a target and location dual-controlled molecular switch. For this proof-of-concept study, fluorescent detection of H2S in lysosomes was performed with a simultaneous H2S and proton-activatable probe based on the acidic environment of lysosomes. The new synthesized fluorescent sensor, "SulpHensor", which contains a spirolactam moiety to bind hydrogen protons and an azide group to react with H2S, displays highly sensitive and selective fluorescence response to H2S under lysosomal pH environment but is out of operation in neutral cytosol and other organelles. Fluorescence imaging shows that SulpHensor is membrane-permeable and suitable for visualization of both the exogenous and endogenous H2S in lysosomes of living cells. The good performance of our proposed approach for H2S sensing demonstrates that this strategy might open up new opportunities for the development of efficient subcellular molecular tools for bioanalytical and biomedical applications.

Reactive oxygen species mediated extracellular polymeric substances production assisting the recovery of Thalassiosira pseudonana from polystyrene micro and nanoplastics exposure.

As emerging pollutants in the aquatic environments, micro- and nano-plastics (MNPs) aroused widespread environmental concerns for their potential threats to the ecological health. Previous research has proved that microalgae growth could recover from the MNPs toxicities, in which the extracellular polymeric substances (EPS) might play the key role. In order to comprehensively investigate the recovery process of microalgae from MNPs stress and the effecting mechanisms of EPS therein, this study conducted a series of experiments by employing two sizes (0.1 and 1 µm) of polystyrene (PS) MNPs and the marine model diatom Thalassiosira pseudonana during 14 days. The results indicated: the pigments accumulations and photosynthetic recovery of T. pseudonana under MPs exposure showed in the early stage (4-5 days), while the elevation of reactive oxygen species (ROS) and EPS contents lasted longer time period (7-8 days). EPS was aggregated with MNPs particles and microalgal cells, corresponding to the increased settlement rates. More increase of soluble (SL)-EPS contents was found than bound (B)-EPS under MNPs exposure, in which the increase of the protein proportion and humic acid-like substances in SL-EPS was found, thus facilitating aggregates formation. ROS was the signaling molecule mediating the overproduction of EPS. The transcriptional results further proved the enhanced EPS biosynthesis on the molecular level. Therefore, this study elucidated the recovery pattern of microalgae from MNPs stress and linked "ROS-EPS production changes-aggregation formation" together during the growth recovery process, with important scientific and environmental significance.

Dissemination of antibiotic resistance genes from aboveground sources to groundwater in livestock farms.

Antibiotic resistant bacteria (ARB) and antibiotic resistance genes (ARGs) are prevalent in various environments on livestock farms, including livestock waste, soil, and groundwater. Contamination of groundwater by ARB and ARGs in livestock farms is a growing concern as it may have potentially huge risks to human health. However, the source of groundwater-borne ARB and ARGs in animal farms remains largely unknown. In this study, different types of samples including groundwater and its potential contamination sources from aboveground (pig feces, wastewater, and soil) from both working and abandoned swine feedlots in southern China were collected and subjected to metagenomic sequencing and ARB isolation. The source tracking based on metagenomic analysis revealed that 56-95 % of ARGs in groundwater was attributable to aboveground sources. Using metagenomic assembly, we found that 45 ARGs predominantly conferring resistance to aminoglycosides, sulfonamides, and tetracyclines could be transferred from the aboveground sources to groundwater, mostly through plasmid-mediated horizontal gene transfer. Furthermore, the full-length nucleotide sequences of sul1, tetA, and TEM-1 detected in ARB isolates exhibited the close evolutionary relationships between aboveground sources and groundwater. Some isolated strains of antibiotic-resistant Pseudomonas spp. from aboveground sources and groundwater had the high similarity (average nucleotide identity > 99 %). Notably, the groundwater-borne ARGs were identified as mainly carried by bacterial pathogens, potentially posing risks to human and animal health. Overall, this study underscores the dissemination of ARGs from aboveground sources to groundwater in animal farms and associated risks.

A High-Energy Tellurium Redox-Amphoteric Conversion Cathode Chemistry for Aqueous Zinc Batteries.

Rechargeable aqueous zinc batteries are potential candidates for sustainable energy storage systems at a grid scale, owing to their high safety and low cost. However, the existing cathode chemistries exhibit restricted energy density, which hinders their extensive applications. Here, a tellurium redox-amphoteric conversion cathode chemistry is presented for aqueous zinc batteries, which delivers a specific capacity of 1223.9 mAh gTe -1 and a high energy density of 1028.0 Wh kgTe -1. A highly concentrated electrolyte (30 mol kg-1 ZnCl2) is revealed crucial for initiating the Te redox-amphoteric conversion as it suppresses the H2O reactivity and inhibits undesirable hydrolysis of the Te4+ product. By carrying out multiple operando/ex situ characterizations, the reversible six-electron Te2-/Te0/Te4+ conversion with TeCl4 is identified as the fully charged product and ZnTe as the fully discharged product. This finding not only enriches the conversion-type battery chemistries but also establishes a critical step in exploring redox-amphoteric materials for aqueous zinc batteries and beyond.

ROS meditated paralytic shellfish toxins production changes of Alexandrium tamarense caused by microplastic particles.

A variety of studies have investigated the toxic effects of microplastics (MPs) on microalgae, but few of them considered their influence on dinoflagellate toxins production, which could cause significant ecological safety concerns in coastal areas. This research investigated the impacts of 5 µg L-1 and 5 mg L-1 polystyrene (PS) MPs on the changes of paralytic shellfish toxins (PSTs) production and their relationship with cellular oxidative stress of Alexandrium tamarense, a common harmful algal blooms causative dinoflagellate. The results showed elevation of reactive oxygen species (ROS) levels, activation of antioxidant system and overproduction of PSTs were positively correlated under PS MPs exposure (especially under 5 mg L-1 PS MPs), and the PSTs changes were eliminated by the ROS inhibitor. Further transcriptomic analysis revealed that ROS could enhance biosynthesis of glutamate, providing raw materials for PSTs precursor arginine, accompanied with enhanced acetyl-CoA and ATP production, finally leading to the overproduction of PSTs. Moreover, the oxidative intracellular environments might block the reduction process from STX to C1&C2, leading to the increase of STX and decrease of C1&C2 proportions. This work brings the first evidence that ROS could mediate PSTs production and compositions of Alexandrium under MPs exposure, with important scientific and ecological significance.

UV-B radiation alleviated detrimental effects of polymethyl methacrylate microplastics on marine diatom Thalassiosira pseudonana.

Microplastics (MPs) in marine environments simultaneously affect microalgae with UV-B radiation, while their joint effecting mechanisms remain largely unknown. To fill this research gap, the joint effects of polymethyl methacrylate (PMMA) MPs and UV-B radiation (natural environments intensity) on the model marine diatom Thalassiosira pseudonana were investigated. Antagonism was found between the two factors with regards to population growth. Furthermore, we found more inhibited population growth and photosynthetic parameters when pre-treated with PMMA MPs compared to pre-treated with UV-B radiation before joint-treated by the two factors. Transcriptional analysis elucidated that UV-B radiation could alleviate the down-regulation of photosynthetic (PSII, cyt b6/f complex and photosynthetic electron transport) and chlorophyll biosynthesis genes caused by PMMA MPs. Besides, the genes encoding carbon fixation and metabolisms was up-regulated under UV-B radiation, which could provide extra energy for the enhanced anti-oxidative activities and DNA replication-repair processes. These consequences showed that the toxicity of PMMA MPs was comprehensively alleviated when T. pseudonana was jointed treated by UV-B radiation. Our results reveled the underlying molecular mechanisms of antagonistic effects between PMMA MPs and UV-B radiation. This study provides important information that environmental factors like UV-B radiation should be considered when accessing the ecological risks of MPs on marine organisms.

Toxicity of 2, 2', 4, 4'-tetrabromodiphenyl ether (BDE-47) on the green microalgae Chlorella sp. and the role of cellular oxidative stress.

Polybrominated diphenyl ethers (PBDEs) are toxic to marine organisms including the major primary producer phytoplankton, while the toxic mechanisms haven't yet been fully clarified. Therefore, we comprehensively studied the toxic mechanisms of BDE-47 on the marine chlorophyte Chlorella sp., with a focus on the role of cellular oxidative stress. The results indicate that BDE-47 stress resulted in the inhibition of population growth as well as cell death and programmed cell death. The antioxidant system was activated in both low and high BDE-47 treatments, but only microalgal cells in the high BDE-47 treatment showed cellular oxidative stress. By adding ROS inhibitor, the relief of photosynthetic inhibition, Ca2+ overproduction and cell death was found. Therefore, we conclude that photosynthetic damage, cell death and cellular oxidative stress were the major mechanisms of BDE-47 toxicity to Chlorella sp., and that cellular oxidative stress played an important role in mediating the other mechanisms.

The effects of two sized polystyrene nanoplastics on the growth, physiological functions, and toxin production of Alexandrium tamarense.

Micro- and nano-plastics (MNPs) are increasingly prevalent pollutants in marine ecosystems and result in various deleterious effects on marine organisms. There have been studies evaluated the toxic effects of MNPs on marine microalgae, but few of them focused on the effects of MNPs on dinoflagellate species and their toxins production, which could have significant implications on human health and ecological safety in coastal areas. In this study, the common harmful algal blooms-causing dinoflagellate Alexandrium tamarense was exposed to 0.1 and 1 µm sized polystyrene nanoplastics (NPs) to investigate the responding patterns of population growth, multiple physiological functions, as well as the intracellular paralytic shellfish toxins (PSTs) productions. The results indicated the population growth, photosynthetic parameters, nutrients (nitrate and phosphate) uptake rates and extracellular carbonic anhydrase activities (CAext) were all inhibited by the two sized NPs, accompanied by the prolonged and more aggregated microalgal cells under the observation of scanning electron microscope (SEM), and the inhibition effects were more severe under 1 µm sized NPs than 0.1 µm sized NPs. Finally, we found the intracellular PSTs contents increased 73.59% exposed to 0.1 µm sized NPs while decreased 85.50% exposed to 1 µm sized NPs comparing the controls at 96 h, without significant changes of relative compositions. These results provided evidence that MNPs were toxic to A. tamarense and affected their intracellular PSTs productions within 96 h, which is critical to consider when evaluating the potential risks of MNPs in marine ecosystems.

The molecular response mechanisms of a diatom Thalassiosira pseudonana to the toxicity of BDE-47 based on whole transcriptome analysis.

Polybrominated diphenyl ethers (PBDEs) are ubiquitously distributed persistent organic pollutants (POPs) in marine environments. Phytoplankton are the entrance of PBDEs entering to biotic environments from abiotic environments, while the responding mechanisms of phytoplankton to PBDEs have not been full established. Therefore, we chose the model diatom Thalassiosira pseudonana in this study, by integrating whole transcriptome analysis with physiological-biochemical data, to reveal the molecular responding mechanisms of T. pseudonana to the toxicity of BDE-47. Our results indicated the changes of genes expressions correlated to the physiological-biochemical changes, and there were multiple molecular mechanisms of T. pseudonana responding to the toxicity of BDE-47: Gene expressions evidence explained the suppression of light reaction and proved the occurrence of cellular oxidative stress; In the meanwhile, up-regulations of genes in pathways involving carbon metabolisms happened, including the Calvin cycle, glycolysis, TCA cycle, fatty acid synthesis, and triacylglycerol synthesis; Lastly, DNA damage was found and three outcome including DNA repair, cell cycle arrest and programmed cell death (PCD) happened, which could finally inhibit the cell division and population growth of T. pseudonana. This study presented the most complete molecular responding mechanisms of phytoplankton cells to PBDEs, and provided valuable information of various PBDEs-sensitive genes with multiple functions for further research involving organic pollutants and phytoplankton.

ROS-mediated programmed cell death (PCD) of Thalassiosira pseudonana under the stress of BDE-47.

Polybrominated diphenyl ethers (PBDEs) are a series of highly persistent organic pollutants (POPs) ubiquitously distributed in marine environments. As key primary producers, microalgae are the start of PBDEs bioaccumulations and vulnerable to their toxicities. In order to deeply investigate the toxic mechanism of PBDEs on microalgal cells, the occurrence of programmed cell death (PCD) in a model diatom Thalassiosira pseudonana and its possible mediating mechanism were studied. The results indicated: cell death of T. pseudonana happened under the stress of BDE-47, which was proved to be PCD based on the correlations with three biochemical markers (DNA fragmentation, phosphatidylserine externalization and caspase activity) and three molecular markers [Metacaspase 2 gene (TpMC2), Death-associated protein gene (DAP3) and Death-specific protein 1 gene (TpDSP1)]; Furthermore, the changes of cellular ROS levels were correlated with the PCD markers and the dead cell rates, and the cell membrane and the chloroplast were identified as the major ROS production sites. Therefore, we concluded that PCD might be an important toxic mechanism of PBDEs on microalgal cells, and that chloroplast- and cell membrane-produced ROS was an important signaling molecule to mediate the PCD activation process. Our research firstly indicated microalgal PCD could be induced by PBDEs, and increased our knowledge of the toxic mechanisms by which POPs affect microalgal cells.