Precise coordination of high-loading Fe single atoms with sulfur boosts selective generation of nonradicals.

Nonradicals are effective in selectively degrading electron-rich organic contaminants, which unfortunately suffer from unsatisfactory yield and uncontrollable composition due to the competitive generation of radicals. Herein, we precisely construct a local microenvironment of the carbon nitride-supported high-loading (~9 wt.%) Fe single-atom catalyst (Fe SAC) with sulfur via a facile supermolecular self-assembly strategy. Short-distance S coordination boosts the peroxymonosulfate (PMS) activation and selectively generates high-valent iron-oxo species (FeIV=O) along with singlet oxygen (1O2), significantly increasing the 1O2 yield, PMS utilization, and p-chlorophenol reactivity by 6.0, 3.0, and 8.4 times, respectively. The composition of nonradicals is controllable by simply changing the S content. In contrast, long-distance S coordination generates both radicals and nonradicals, and could not promote reactivity. Experimental and theoretical analyses suggest that the short-distance S upshifts the d-band center of the Fe atom, i.e., being close to the Fermi level, which changes the binding mode between the Fe atom and O site of PMS to selectively generate 1O2 and FeIV=O with a high yield. The short-distance S-coordinated Fe SAC exhibits excellent application potential in various water matrices. These findings can guide the rational design of robust SACs toward a selective and controllable generation of nonradicals with high yield and PMS utilization.

Multifunctional biomolecular corona-inspired nanoremediation of antibiotic residues.

Facing complex and variable emerging antibiotic pollutants, the traditional development of functional materials is a "trial-and-error" process based on physicochemical principles, where laborious steps and long timescales make it difficult to accelerate technical breakthroughs. Notably, natural biomolecular coronas derived from highly tolerant organisms under significant contamination scenarios can be used in conjunction with nanotechnology to tackling emerging contaminants of concern. Here, super worms (Tubifex tubifex) with high pollutant tolerance were integrated with nano-zero valent iron (nZVI) to effectively reduce the content of 17 antibiotics in wastewater within 7 d. Inspired by the synergistic remediation, nZVI-augmented worms were constructed as biological nanocomposites. Neither nZVI (0.3 to 3 g/L) nor worms (104 to 105 per liter) alone efficiently degraded florfenicol (FF, as a representative antibiotic), while their composite removed 87% of FF (3 µmol/L). Under antibiotic exposure, biomolecules secreted by worms formed a corona on and modified the nZVI particle surface, enabling the nano-bio interface greater functionality, including responsiveness, enrichment, and reduction. Mechanistically, FF exposure activated glucose-alanine cycle pathways that synthesize organic acids and amines as major metabolites, which were assembled into vesicles and secreted, thereby interacting with nZVI in a biologically response design strategy. Lactic acid and urea formed hydrogen bonds with FF, enriched analyte presence at the heterogeneous interface. Succinic and lactic acids corroded the nZVI passivation layer and promoted electron transfer through surface conjugation. This unique strategy highlights biomolecular coronas as a complex resource to augment nano-enabled technologies and will provide shortcuts for rational manipulation of nanomaterial surfaces with coordinated multifunctionalities.

Metagenomic and proteomic insights into the self-adaptive cell surface hydrophobicity of Sphingomonas sp. strain PAH02 reducing the migration of cadmium-phenanthrene co-pollutant in rice.

Cell surface hydrophobicity (CSH) dominates the interactions between rhizobacteria and pollutants at the soil-water interface, which is critical for understanding the dissipation of pollutants in the rhizosphere microzone of rice. Herein, we explored the effects of self-adaptive CSH of Sphingomonas sp. strain PAH02 on the translocation and biotransformation behaviour of cadmium-phenanthrene (Cd-Phe) co-pollutant in rice and rhizosphere microbiome. We evidenced that strain PAH02 reduced the adsorption of Cd-Phe co-pollutant on the rice root surface while enhancing the degradation of Phe and adsorption of Cd via its self-adaptive CSH in the hydroponic experiment. The significant upregulation of key protein expression levels such as MerR, ARHDs and enoyl-CoA hydratase/isomerase, ensures self-adaptive CSH to cope with the stress of Cd-Phe co-pollutant. Consistently, the bioaugmentation of strain PAH02 promoted the formation of core microbiota in the rhizosphere soil of rice (Oryza sativa L.), such as Bradyrhizobium and Streptomyces and induced gene enrichment of CusA and PobA that are strongly associated with pollutant transformation. Consequently, the contents of Cd and Phe in rice grains at maturity decreased by 17.2% ± 0.2% and 65.7% ± 0.3%, respectively, after the bioaugmentation of strain PAH02. These findings present new opportunities for the implementation of rhizosphere bioremediation strategies of co-contaminants in paddy fields.

D-Ring Modifications of Tetracyclines Determine Their Ability to Induce Resistance Genes in the Environment.

The widespread utilization of tetracyclines (TCs) in agriculture and medicine has led to the borderless spread of tetracycline resistance in humans, animals, and the environment, posing huge risks to both the ecosystem and human society. Changes in the functional group modifications resulted in a higher bacteriostatic efficacy of the new generation of TCs, but their effect on the emergence and evolution of antibiotic resistance genes (ARGs) is not yet known. To this end, four TCs from three generations were chosen to compare their structural effects on influencing the evolution of ARGs in soil microbial communities. The findings revealed that low-generation TCs, such as tetracycline and oxytetracycline, exhibited a greater propensity to stimulate the production and proliferation of ARGs than did high-generation tigecycline. Molecular docking analysis demonstrated that modifications of the D-ring functional group determined the binding capacity of TCs to the substrate-binding pocket of transcriptional regulators and efflux pumps mainly involved in drug resistance. This can be further evidenced by reverse transcription-quantitative polymerase chain reaction quantification and intracellular antibiotic accumulation assessment. This study sheds light on the mechanism of the structural effect of antibiotic-induced ARG production from the perspective of compound-protein binding, therefore providing theoretical support for controlling the dissemination of antibiotic resistance.

Unveiling the Mechanism and Kinetics of Pollutant Attenuation by Free Radicals Triggered from Goethite in Water Distribution Systems.

Investigating the fate of persistent organic pollutants in water distribution systems (WDSs) is of great significance for preventing human health risks. The role of iron corrosion scales in the migration and transformation of organics in such systems remains unclear. Herein, we determined that hydroxyl (•OH), chlorine, and chlorine oxide radicals are generated by Fenton-like reactions due to the coexistence of oxygen vacancy-related Fe(II) on goethite (a major constituent of iron corrosion scales) and hypochlorous acid (HClO, the main reactive chlorine species of residual chlorine at pH ∼ 7.0). •OH contributed mostly to the decomposition of atrazine (ATZ, model compound) more than other radicals, producing a series of relatively low-toxicity small molecular intermediates. A simplified kinetic model consisting of mass transfer of ATZ and HClO, •OH generation, and ATZ oxidation by •OH on the goethite surface was developed to simulate iron corrosion scale-triggered residual chlorine oxidation of organic compounds in a WDS. The model was validated by comparing the fitting results to the experimental data. Moreover, the model was comprehensively applicable to cases in which various inorganic ions (Ca2+, Na+, HCO3-, and SO42-) and natural organic matter were present. With further optimization, the model may be employed to predict the migration and accumulation of persistent organic pollutants under real environmental conditions in the WDSs.

Aerobic Microbial Transformation of Fluorinated Liquid Crystal Monomer: New Pathways and Mechanism.

Fluorinated liquid crystal monomers (FLCMs) have been suggested as emerging contaminants, raising global concern due to their frequent occurrence, potential toxic effects, and endurance capacity in the environment. However, the environmental fate of the FLCMs remains unknown. To fill this knowledge gap, we investigated the aerobic microbial transformation mechanisms of an important FLCM, 4-[difluoro(3,4,5-trifluorophenoxy)methyl]-3, 5-difluoro-4'-propylbiphenyl (DTMDPB), using an enrichment culture termed as BG1. Our findings revealed that 67.5 ± 2.1% of the initially added DTMDPB was transformed in 10 days under optimal conditions. A total of 14 microbial transformation products obtained due to a series of reactions (e.g., reductive defluorination, ether bond cleavage, demethylation, oxidative hydroxylation and aromatic ring opening, sulfonation, glucuronidation, O-methylation, and thiolation) were identified. Consortium BG1 harbored essential genes that could transform DTMDPB, such as dehalogenation-related genes [e.g., glutathione S-transferase gene (GST), 2-haloacid dehalogenase gene (2-HAD), nrdB, nuoC, and nuoD]; hydroxylating-related genes hcaC, ubiH, and COQ7; aromatic ring opening-related genes ligB and catE; and methyltransferase genes ubiE and ubiG. Two DTMDPB-degrading strains were isolated, which are affiliated with the genus Sphingopyxis and Agromyces. This study provides a novel insight into the microbial transformation of FLCMs. The findings of this study have important implications for the development of bioremediation strategies aimed at addressing sites contaminated with FLCMs.

Controllable chemical redox reactions to couple microbial degradation for organic contaminated sites remediation: A review.

Global environmental concern over organic contaminated sites has been progressively conspicuous during the process of urbanization and industrial restructuring. While traditional physical or chemical remediation technologies may significantly destroy the soil structure and function, coupling moderate chemical degradation with microbial remediation becomes a potential way for the green, economic, and efficient remediation of contaminated sites. Hence, this work systematically elucidates why and how to couple chemical technology with microbial remediation, mainly focused on the controllable redox reactions of organic contaminants. The rational design of materials structure, selective generation of reactive oxygen species, and estimation of degradation pathway are described for chemical oxidation. Meanwhile, current progress on efficient and selective reductions of organic contaminants (i.e., dechlorination, defluorination, -NO2 reduction) is introduced. Combined with the microbial remediation of contaminated sites, several consideration factors of how to couple chemical and microbial remediation are proposed based on both fundamental and practical points of view. This review will advance the understanding and development of chemical-microbial coupled remediation for organic contaminated sites.

Pollution characteristics and source apportionment of heavy metal(loid)s in soil and groundwater of a retired industrial park.

Heavy metal(loid)s (HMs) pollution has become a common and complex problem in industrial parks due to rapid industrialization and urbanization. Here, soil and groundwater were sampled from a retired industrial park to investigate the pollution characteristics of HMs. Results show that Ni, Pb, Cr, Zn, Cd, and Cu were the typical HMs in the soil. Source analysis with the positive matrix factorization model indicates that HMs in the topsoil stemmed from industrial activities, traffic emission, and natural source, and the groundwater HMs originated from industrial activities, groundwater-soil interaction, groundwater-rock interaction, and atmosphere deposition. The sequential extraction of soil HMs reveals that As and Hg were mainly distributed in the residue fraction, while Ni, Pb, Cr, Zn, Cd, and Cu mainly existed in the mobile fraction. Most HMs either in the total concentration or in the bioavailable fraction preferred to retain in soil as indicated by their high soil-water partitioning coefficients (Kd), and the Kd values were correlated with soil pH, groundwater redox potential, and dissolved oxygen. The relative stable soil-groundwater circumstance and the low active fraction contents limited the vertical migration of soil HMs and their release to groundwater. These findings increase our knowledge about HMs pollution characteristics of traditional industrial parks and provide a protocol for HMs pollution scrutinizing in large zones.

Amino Acid Transporter as a Potential Carrier Protein for the Root-to-Shoot Translocation of Polybrominated Diphenyl Ethers in Rice.

As typical persistent organic pollutants, polybrominated diphenyl ethers (PBDEs) tend to accumulate in edible parts of rice, posing great ecological and health risks. The translocation of PBDEs from underground to aboveground parts of rice is a crucial procedure to determine the final bioaccumulation level. Herein, this study aimed to identify the transporter proteins for PBDEs in rice plants in order to strengthen our understanding of the bioaccumulation mechanism and the potential prevention strategy of the PBDE risk. Similar time-dependent patterns were observed among the root-to-shoot translocation factors (TFs) of PBDEs, the expression of lysine histidine transporter (LHT) protein, and the relative levels of LHT substrates (phenylalanine or tyrosine), implying the potential co-transport of PBDEs, phenylalanine, and tyrosine by the carrier LHT. Fluorescence spectra and circular dichroism showed that PBDE congeners interfered with LHT via static fluorescence quenching and changes in the protein's secondary structure. The in vitro sorption fraction of LHT to PBDEs, as revealed by sorption equilibrium analysis, was comparable to the in vivo TF values. Knockout of OsLHT1 in rice using CRISPR/Cas9 technology caused a 48.2-78.4% decrease in PBDE translocation. Molecular docking simulation suggested that PBDEs, phenylalanine, and tyrosine were inserted into the same ligand-binding cavity of LHT, substantiating the potential carrier role of LHT for PBDEs from a conformational perspective. Quantitative structure activity relationship analysis demonstrated that the ether-bond oxygen and the carbons at the site 4 and 4' of PBDE molecules are significant determinants of the binding affinity with the LHT protein and in vivo translocation of PBDEs. In summary, this study discovered that LHT acts as the cellular carrier for PBDEs and offered a comprehensive molecular explanation for the bioaccumulation and translocation of PBDEs in rice plants, covering both biological and chemical perspectives. These findings fill in a knowledge gap on the endogenous transporter proteins for exogenous organic pollutants.

Potential Toxic Mechanisms of Neonicotinoid Insecticides in Rice: Inhibiting Auxin-Mediated Signal Transduction.

Inappropriate application of pesticides not only causes sub-lethal effects on ecosystem service providers but also reduces crop yield and quality. As a xenobiotic signal molecule, pesticides may interact with signal transduction receptors in crops, resulting in oxidative damage and even metabolic perturbations. We discovered that three neonicotinoid insecticides (NIs), namely, imidacloprid, thiamethoxam, and clothianidin, at 0.06-0.12 kg ai/ha significantly inhibited the auxin signal pathway in rice leaves, thereby reducing the intracellular auxin (IAA) content. Molecular simulation further confirmed that NIs occupied the binding site where auxin transporter-like proteins 1 (LAX11) and 2 (LAX12), in which Thr253 and Asn66 of LAX11, as well as Thr244 and Asn57 of LAX12, were bound to the nitroguanidine of NIs via H-bonds. Meanwhile, Asn66 of LAX11 and Asn57 of LAX12 interacted with nitroguanidine via aromatic H-bonds. Moreover, phenylpropanoid biosynthesis was significantly disturbed because of the inhibited auxin signal pathway. Notably, peroxidase-coding genes were downregulated with a maximum value greater than 10-fold, resulting in decreased antioxidant metabolites flavone (37.82%) and lignin content (20.15%). Ultimately, rice biomass was reduced by up to 25.41% due to the decline in IAA content and antioxidant capacity. This study deeply explored the molecular mechanism of metabolic perturbations in crops stressed by pesticides, thus providing a scientific basis for pesticide environmental risk assessment and agricultural product safety.

Benzotriazole Ultraviolet Stabilizers (BUVSs) as Potential Protein Kinase Antagonists in Rice.

The ubiquitous occurrence of benzotriazole ultraviolet stabilizers (BUVSs) in the environment and organisms has warned of their potential ecological and health risks. Studies showed that some BUVSs exerted immune and chronic toxicities to animals by disturbing signaling transduction, yet limited research has investigated the toxic effects on crop plants and the underlying mechanisms of signaling regulation. Herein, a laboratory-controlled hydroponic experiment was conducted on rice to explore the phytotoxicity of BUVSs by integrating conventional biochemical experiments, transcriptomic analysis, competitive sorption assays, and computational studies. The results showed that BUVSs inhibited the growth of rice by 6.30-20.4% by excessively opening the leaf stomas, resulting in increased transpiration. BUVSs interrupted the transduction of abscisic acid (ABA) signal through competitively binding to Ca2+-dependent protein kinase (CDPK), weakening the CDPK phosphorylation and further inhibiting the downstream signaling. As structural analogues of ATP, BUVSs acted as potential ABA signaling antagonists, leading to physiological dysfunction in mediating stomatal closure under stresses. This is the first comprehensive study elucidating the effects of BUVSs on the function of key proteins and the associated signaling transduction in plants and providing insightful information for the risk evaluation and control of BUVSs.

Deterministic Effect of pH on Shaping Soil Resistome Revealed by Metagenomic Analysis.

Soil is recognized as the major reservoir of antibiotic resistance genes (ARGs), harboring the most diverse naturally evolved ARGs on the planet. Multidrug resistance genes are a class of ARGs, and their high prevalence in natural soil ecosystems has recently raised concerns. Since most of these genes express proton motive force (PMF) driven efflux pumps, studying whether soil pH is a determinant for the selection of multidrug efflux pump genes and thus shaping the soil resistome are of great interest. In this study, we collected 108 soils with pH values ranging from 4.37 to 9.69 from multiple ecosystems and profiled the composition of ARGs for metagenomes and metagenome-assembled genomes. We observed the multidrug efflux pump genes enriched in the acidic soil resistome, and their abundances have significant soil pH dependence. This reflects the benefits of high soil proton activity on the multidrug efflux pump genes, especially for the PMF-driven inner membrane transferase. In addition, we preliminary indicate the putative microbial participants in pH shaping the soil resistome by applying ecological analyzing tools such as stepwise regression and random forest model fitting. The decisive influence of proton activity on shaping the resistome is more impactful than any other examined factors, and as the consequence, we revisited the influence of edaphic factors on the soil resistome; i.e., the deterministic selection of resistance mechanisms by edaphic factors could lead to the bottom-up shaping of the ARG composition. Such natural developing mechanisms of the resistome are herein suggested to be considered in assessing human-driven ARG transmissions.

Nematodes Degrade Extracellular Antibiotic Resistance Genes by Secreting DNase II Encoded by the nuc-1 Gene.

This study investigated the degradation performance and mechanism of extracellular antibiotic resistance genes (eARGs) by nematodes using batch degradation experiments, mutant strain validation, and phylogenetic tree construction. Caenorhabditis elegans, a representative nematode, effectively degraded approximately 99.999% of eARGs (tetM and kan) in 84 h and completely deactivated them within a few hours. Deoxyribonuclease (DNase) II encoded by nuc-1 in the excretory and secretory products of nematodes was the primary mechanism. A neighbor-joining phylogenetic tree indicated the widespread presence of homologs of the NUC-1 protein in other nematodes, such as Caenorhabditis remanei and Caenorhabditis brenneri, whose capabilities of degrading eARGs were then experimentally confirmed. C. elegans remained effective in degrading eARGs under the effects of natural organic matter (5, 10, and 20 mg/L, 5.26-6.22 log degradation), cation (2.0 mM Mg2+ and 2.5 mM Ca2+, 5.02-5.04 log degradation), temperature conditions (1, 20, and 30 °C, 1.21-5.26 log degradation), and in surface water and wastewater samples (4.78 and 3.23 log degradation, respectively). These findings highlight the pervasive but neglected role of nematodes in the natural decay of eARGs and provide novel approaches for antimicrobial resistance mitigation biotechnology by introducing nematodes to wastewater, sludge, and biosolids.

Efficient Degradation of Intracellular Antibiotic Resistance Genes by Photosensitized Erythrosine-Produced 1O2.

Intracellular antibiotic resistance genes (iARGs) constitute the important part of wastewater ARGs and need to be efficiently removed. However, due to the dual protection of intracellular DNA by bacterial membranes and the cytoplasm, present disinfection technologies are largely inefficient in iARG degradation. Herein, we for the first time found that erythrosine (ERY, an edible dye) could efficiently degrade iARGs by producing abundant 1O2 under visible light. Seven log antibiotic-resistant bacteria were inactivated within only 1.5 min, and 6 log iARGs were completely degraded within 40 min by photosensitized ERY (5.0 mg/L). A linear relationship was established between ARG degradation rate constants and 1O2 concentrations in the ERY photosensitizing system. Surprisingly, a 3.2-fold faster degradation of iARGs than extracellular ARGs was observed, which was attributed to the unique indirect oxidation of iARGs induced by 1O2. Furthermore, ERY photosensitizing was effective for iARG degradation in real wastewater and other photosensitizers (including Rose Bengal and Phloxine B) of high 1O2 yields could also achieve efficient iARG degradation. The findings increase our knowledge of the iARG degradation preference by 1O2 and provide a new strategy of developing technologies with high 1O2 yield, like ERY photosensitizing, for efficient iARG removal.

Improved Electronic Structure from Spin-State Reconstruction of a Heteronuclear Fe-Co Diatomic Pair to Boost the Fenton-like Reaction.

Dual-atom catalysts (DACs) are promising candidates for various catalytic reactions, including electrocatalysis, chemical synthesis, and environmental remediation. However, the high-activity origin and mechanism underlying intrinsic activity enhancement remain elusive, especially for the Fenton-like reaction. Herein, we systematically compared the catalytic performance of dual-atom FeCo-N/C with its single-atom counterparts by activating peroxymonosulfate (PMS) for pollutant abatement. The unusual spin-state reconstruction on FeCo-N/C is demonstrated to effectively improve the electronic structure of Fe and Co in the d orbital and enhance the PMS activation efficiency. Accordingly, the dual-atom FeCo-N/C with an intermediate-spin state remarkably boosts the Fenton-like reaction by almost 1 order of magnitude compared with low-spin Co-N/C and high-spin Fe-N/C. Moreover, the established dual-atom-activated PMS system also exhibits excellent stability and robust resistance against harsh conditions. Combined theoretical calculations reveal that unlike unitary Co atom or Fe atom transferring electrons to the PMS molecule, the Fe atom of FeCo-N/C provides extra electrons to the neighboring Co atom and positively shifts the d band of the Co center, thereby optimizing the PMS adsorption and decomposition into a unique high-valent FeIV-O-CoIV species via a low-energy barrier pathway. This work advances a conceptually novel mechanistic understanding of the enhanced catalytic activity of DACs in Fenton-like reactions and helps to expand the application of DACs in various catalytic reactions.

Methoxylated Modification of Glutathione-Mediated Metabolism of Halobenzoquinones In Vivo and In Vitro.

Xenobiotics were generally detoxified in organisms through interaction with endogenous molecules, which may also generate metabolites of increased toxicity. Halobenzoquinones (HBQs), a group of highly toxic emerging disinfection byproducts (DBPs), can be metabolized by reacting with glutathione (GSH) to form various glutathionylated conjugates (SG-HBQs). In this study, the cytotoxicity of HBQs in CHO-K1 cells showed a wavy curve as a function of increased GSH dosage, which was inconsistent with the commonly recognized progressive detoxification curve. We hypothesized that the formation and cytotoxicity of GSH-mediated HBQ metabolites contribute to the unusual wave-shaped cytotoxicity curve. Results showed that glutathionyl-methoxyl HBQs (SG-MeO-HBQs) were identified to be the primary metabolites significantly correlated with the unusual cytotoxicity variation of HBQs. The formation pathway was initiated by stepwise metabolism via hydroxylation and glutathionylation to produce detoxified hydroxyl HBQs (OH-HBQs) and SG-HBQs, followed by methylation to generate SG-MeO-HBQs of potentiated toxicity. To further verify the occurrence of the aforementioned metabolism in vivo, SG-HBQs and SG-MeO-HBQs were detected in the liver, kidney, spleen, testis, bladder, and feces of HBQ-exposed mice, with the highest concentration quantified in the liver. The present study supported that the co-occurrence of metabolism can be antagonistic, which enhanced our understanding of the toxicity and metabolic mechanism of HBQs.

Interaction between Phthalate Ester and Rice Plants: Novel Transformation Pathways and Metabolic-Network Perturbations.

Our understanding is limited concerning the interaction mechanism between widespread phthalate esters and staple crops, which have strong implications for human exposure. Therefore, this study was aimed at illuminating the transformation pathways of di-n-butyl phthalate (DnBP) in rice using an untargeted screening method. UPLC-QTOF-MS identified 16 intermediate transformation products formed through hydroxylation, hydrolysis, and oxidation in phase I metabolism and further by conjugation with amino acids, glutathione, and carbohydrates in phase II metabolism. Mono-2-hydroxy-n-butyl phthalate-l-aspartic acid (MHBP-asp) and mono-2-hydroxy-n-butyl phthalate-d-alanyl-ß-d-glucoside (MHBP-ala-glu) products were observed for the first time. The proteomic analysis demonstrated that DnBP upregulated the expression of rice proteins associated with transporter activity, antioxidant synthesis, and oxidative stress response and downregulated that of proteins involved in photosynthesis, photorespiration, chlorophyll binding, and mono-oxygenase activity. Molecular docking revealed that DnBP can affect protein molecular activity via pi-sigma, pi-alkyl, and pi-pi interactions or by forming carbon-hydrogen bonds. The metabolomic analysis showed that key metabolic pathways including citrate cycle, biosynthesis of aminoacyl-tRNA, and metabolism of amino acids, sphingolipids, carbohydrates, nucleotides, and glutathione were activated in rice plants exposed to DnBP and its primary metabolite mono-n-butyl phthalate (MnBP). Furthermore, exposure to 80 ng/mL MnBP significantly perturbed the metabolic profile and molecular function in plants, with downregulation of the levels of beta-alanine (0.56-fold), cytosine (0.48-fold), thymine (0.62-fold), uracil (0.48-fold), glucose (0.59-fold), and glucose-1-phosphate (0.33-fold), as well as upregulation of the levels of l-glutamic acid (2.97-fold), l-cystine (2.69-fold), and phytosphingosine (38.38-fold). Therefore, the degradation intermediates of DnBP pose a potentially risk to plant metabolism and raise concerns for crop safety related to plasticizer pollution.

Biotransformation of Organophosphate Esters by Rice and Rhizosphere Microbiome: Multiple Metabolic Pathways, Mechanism, and Toxicity Assessment.

The biotransformation behavior and toxicity of organophosphate esters (OPEs) in rice and rhizosphere microbiomes were comprehensively studied by hydroponic experiments. OPEs with lower hydrophobicity were liable to be translocated acropetally, and rhizosphere microbiome could reduce the uptake and translocation of OPEs in rice tissues. New metabolites were successfully identified in rice and rhizosphere microbiome, including hydrolysis, hydroxylated, methylated, and glutathione-, glucuronide-, and sulfate-conjugated products. Rhizobacteria and plants could cooperate to form a complex ecological interaction web for OPE elimination. Furthermore, active members of the rhizosphere microbiome during OPE degradation were revealed and the metagenomic analysis indicated that most of these active populations contained OPE-degrading genes. The results of metabolomics analyses for phytotoxicity assessment implied that several key function metabolic pathways of the rice plant were found perturbed by metabolites, such as diphenyl phosphate and monophenyl phosphate. In addition, the involved metabolism mechanisms, such as the carbohydrate metabolism, amino acid metabolism and synthesis, and nucleotide metabolism in Escherichia coli, were significantly altered after exposure to the products mixture of OPEs generated by rhizosphere microbiome. This work for the first time gives a comprehensive understanding of the entire metabolism of OPEs in plants and associated microbiome, and provides support for the ongoing risk assessment of emerging contaminants and, most critically, their transformation products.

Development and challenges of smart actuators based on water-responsive materials.

Water-responsive (WR) materials, due to their controllable mechanical response to humidity without energy actuation, have attracted lots of attention to the development of smart actuators. WR material-based smart actuators can transform natural humidity to a required mechanical motion and have been widely used in various fields, such as soft robots, micro-generators, smart building materials, and textiles. In this paper, the development of smart actuators based on different WR materials has been reviewed systematically. First, the properties of different biological WR materials and the corresponding actuators are summarized, including plant materials, animal materials, and microorganism materials. Additionally, various synthetic WR materials and their related applications in smart actuators have also been introduced in detail, including hydrophilic polymers, graphene oxide, carbon nanotubes, and other synthetic materials. Finally, the challenges of the WR actuator are analyzed from the three perspectives of actuator design, control methods, and compatibility, and the potential solutions are also discussed. This paper may be useful for the development of not only soft actuators that are based on WR materials, but also smart materials applied to renewable energy.

Molecular Structure and Sulfur Content Affect Reductive Dechlorination of Chlorinated Ethenes by Sulfidized Nanoscale Zerovalent Iron.

Sulfidized nanoscale zerovalent iron (SNZVI) with desirable properties and reactivity has recently emerged as a promising groundwater remediation agent. However, little information is available on how the molecular structure of chlorinated ethenes (CEs) affects their dechlorination by SNZVI or whether the sulfur content of SNZVI can alter their dechlorination pathway and reactivity. Here, we show that the reactivity (up to 30-fold) and selectivity (up to 70-fold) improvements of SNZVI (compared to NZVI) toward CEs depended on the chlorine number, chlorine position, and sulfur content. Low CEs (i.e., vinyl chloride and cis-1,2-dichloroethene) and high CEs (perchloroethene) tended to be dechlorinated by SNZVI primarily via atomic H and direct electron transfer, respectively, while SNZVI could efficiently and selectively dechlorinate trichloroethene and trans-1,2-dichloroethene via both pathways. Increasing the sulfidation degree of SNZVI suppressed its ability to produce atomic H but promoted electron transfer and thus altered the relative contributions of atomic H and electron transfer to the CE dechlorination, resulting in different reactivities and selectivities. These were indicated by the correlations of CE dechlorination rates and improvements with CE molecular descriptors, H2 evolution rates, and electron transfer indicators of SNZVI. These mechanistic insights indicate the importance of determining the structure-specific properties and reactivity of both SNZVI materials and their target contaminants and can lead to a more rational design of SNZVI for in situ groundwater remediation of various CEs.